Exam Specifications
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A Level
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GCSE Physics
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Key Stage 4
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AQA GCSE Additional Science (4463) Biology
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AQA GCSE Additional Science (4463) Chemistry
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I. Chemistry 2
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1. How do sub-atomic particles help us to understand the structure of substances?
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All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of protons.
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An ionic compound is a giant structure of ions. Ionic compounds are held together by strong forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding.
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Atoms have a small central nucleus made up of protons and neutrons around which there are electrons. The relative electrical charges are as shown: Proton +1 ; Neutron 0 ; Electron –1
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Chemical bonding involves either transferring or sharing electrons in the highest occupied energy levels (shells) of atoms.
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Compounds are substances in which atoms of two, or more, elements are not just mixed together but chemically combined.
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Electrons occupy particular energy levels. Each electron in an atom is at a particular energy level (shell). The electrons in an atom occupy the lowest available energy levels (innermost available shells).
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Elements in the same group in the periodic table have the same number of electrons in the highest energy levels (outer electrons).
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In an atom, the number of electrons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge.
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Metals consist of giant structures of atoms arranged in a regular pattern. The electrons in the highest occupied energy levels (outer shell) of metal atoms are delocalised and so free to move through the whole structure.
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The elements in Group 1 of the periodic table, the alkali metals, have similar chemical properties. They all react with non-metal elements to form ionic compounds in which the metal ion has a single positive charge.
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The elements in Group 7 of the periodic table, the halogens, have similar chemical properties. They react with the alkali metals to
form ionic compounds in which the halide ions have a single negative charge.
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The number of protons in an atom is called its atomic number (proton number). Atoms are arranged in the modern periodic table in order of their atomic number (proton number).
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to represent the bonding in metals in the following form: schematic representation of the shell structure of atoms in metals or model of crystal lattice of metals.
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to represent the covalent bonds in molecules such as water, ammonia, hydrogen, hydrogen chloride, chlorine, methane and oxygen and in giant structures such as diamond and silicon dioxide in the different forms.
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to represent the electronic structure of the first twenty elements of the periodic table in the following forms: for sodium - schematic representation of the shell structure and number of electrons placed in each shell (2,8,1).
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to represent the electronic structure of the ions in sodium chloride, magnesium oxide and calcium chloride in the following forms:
for sodium ion (Na+ ) and illustration 2. and [2,8]+
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to write balanced chemical equations for reactions.
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When atoms form chemical bonds by transferring electrons, they form ions. Atoms that lose electrons become positively charged ions. Atoms that gain electrons become negatively charged ions. Ions have the electronic structure of a noble gas.
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When atoms share pairs of electrons, they form covalent bonds (strong). Some covalently bonded substances consist of simple molecules such as H2, Cl2, O2, HCl, H2O and CH4. Others have giant covalent structures, such as diamond and silicon dioxide.
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2. How do structures influence the properties and uses of substances?
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Atoms that share electrons can also form giant structures or macromolecules. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures (lattices) of atoms (with very high melting points).
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In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard.
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In graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other and so graphite is soft and slippery.
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In graphite, one electron from each carbon atom is delocalised. These delocalised electrons allow graphite to conduct heat and electricity.
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Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces in all directions between oppositely charged ions. These compounds have high
melting points and high boiling points.
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Metals conduct heat and electricity because of the delocalised electrons in their structures.
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Nanoscience refers to structures that are 1-100 nm in size, of the order of a few hundred atoms. Nanoparticles show different properties to the same materials in bulk and have a high surface area to volume ratio, which may lead to new developments.
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Substances that consist of simple molecules are gases, liquids or solids that have relatively low melting points and boiling points.
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Substances that consist of simple molecules do not conduct electricity because the molecules do not have an overall electric charge.
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Substances that consist of simple molecules have only weak forces between the molecules (intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.
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The layers of atoms in metals are able to slide over each other and so metals can be bent and shaped.
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to evaluate developments and applications of new materials, eg nanomaterials, smart materials.
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to relate the properties of substances to their uses
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to suggest the type of structure of a substance given its properties
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When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and carry the current.
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3. How much can we make and how much do we need to use?
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Although reversible reactions may not go to completion, they can still be used efficiently in continuous industrial processes, such as the Haber process that is used to manufacture ammonia.
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Atoms can be represented as symbol of element with mass number and atomic number.
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Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element.
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Even though no atoms are gained or lost in a chemical reaction, it is not always possible to obtain the calculated amount of a product. Explain why.
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In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called reversible reactions and are represented by using double arrow.
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On cooling, the ammonia liquefies and is removed. The remaining hydrogen and nitrogen is re-cycled.
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The amount of a product obtained is known as the yield. When compared with the maximum theoretical amount as a percentage, it is called the percentage yield.
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The atom economy (atom utilisation) is a measure of the amount of starting materials that end up as useful products. It is important
for sustainable development and for economical reasons to use reactions with high atom economy.
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The masses of reactants and products can be calculated from balanced symbol equations.
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The percentage of an element in a compound can be calculated from the relative mass of the element in the formula and the relative formula mass of the compound.
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The purified gases are passed over a catalyst of iron at a high temperature and a high pressure. Some of the hydrogen and nitrogen reacts to form ammonia. The reaction is reversible so ammonia breaks down again into nitrogen and hydrogen.
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The raw materials for the Haber process are nitrogen and hydrogen. Nitrogen is obtained from the air and hydrogen may be obtained from natural gas or other sources.
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The reaction conditions are chosen to produce a reasonable yield of ammonia quickly.
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The relative amounts of all the reacting substances at equilibrium depend on the conditions of the reaction.
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The relative atomic mass of an element (Ar) compares the mass of atoms of the element with the 12C isotope. It is an average value
for the isotopes of the element.
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The relative formula mass (Mr) of a compound is the sum of the relative atomic masses of the atoms in the numbers shown in the
formula.
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The relative formula mass of a substance, in grams, is known as one mole of that substance.
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The relative masses of protons, neutrons and electrons are: Proton - 1 ; Neutron - 1 ; Electron - very small
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The total number of protons and neutrons in an atom is called its mass number.
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to calculate chemical quantities involving empirical formulae reacting masses and percentage yield
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to calculate chemical quantities involving formula mass (Mr) and percentages of elements in compounds
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to calculate the atom economy for industrial processes and be able to evaluate sustainable development issues related to this economy.
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When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction.
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4. How can we control the rates of chemical reactions?
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5. Do chemical reactions always release energy?
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An endothermic reaction is one that takes in energy, often as heat, from the surroundings. Endothermic reactions include thermal decompositions.
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An exothermic reaction is one that transfers energy, often as heat, to the surroundings. Examples of exothermic reactions include combustion, many oxidation reactions and neutralisation.
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If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction. The same amount of energy is transferred in each case.
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If the temperature is lowered, the yield from the endothermic reaction decreases and the yield from the exothermic reaction increases.
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If the temperature is raised, the yield from the endothermic reaction increases and the yield from the exothermic reaction decreases.
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In gaseous reactions, an increase in pressure will favour the reaction that produces the least number of molecules as shown by the symbol equation for that reaction.
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It is important for sustainable development as well as economic reasons to minimise energy requirements and energy wasted in industrial processes. Non-vigorous conditions mean less energy is used and less is released into the environment.
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The relative amounts of all the reacting substances at equilibrium depend on the conditions of the reaction.
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These factors, together with reaction rates, are important when determining the optimum conditions in industrial processes, including the Haber process.
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to describe the effects of changing the conditions of temperature and pressure on a given reaction or process
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to evaluate the conditions used in industrial processes in terms of energy requirements.
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When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction.
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When chemical reactions occur, energy is transferred to or from the surroundings.
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6. How can we use ions in solutions?
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Ammonia dissolves in water to produce an alkaline solution. It is used to produce ammonium salts. Ammonium salts are important
as fertilisers.
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At the negative electrode, positively charged ions gain electrons (reduction) and at the positive electrode, negatively charged ions lose electrons (oxidation).
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Copper can be purified by electrolysis using a positive electrode made of the impure copper and a negative electrode of pure copper in a solution containing copper ions.
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During electrolysis, positively charged ions move to the negative electrode, and negatively charged ions move to the positive electrode.
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Hydrogen ions H+ (aq) make solutions acidic and hydroxide ions – OH-(aq) make solutions alkaline. The pH scale is a measure of the acidity or alkalinity of a solution.
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If there is a mixture of ions, the products formed depend on the reactivity of the elements involved.
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In neutralisation reactions, hydrogen ions react with hydroxide ions to produce water. This reaction can be represented by the
equation: H+ (aq) + OH-(aq) -› H2O(l).
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Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. Precipitation can be used to remove unwanted ions from solutions, for example in treating water for drinking or in treating effluent.
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Metal oxides and hydroxides are bases. Soluble hydroxides are called alkalis.
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Passing an electric current through ionic substances that are molten or in solution breaks them down into elements. This process is called electrolysis.
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Reactions at electrodes can be represented by half equations, for example:
2Cl- - › Cl2 + 2e-
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Salt solutions can be crystallised to produce solid salt.
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Soluble salts can be made from acids by reacting them with:
- metals,
- insoluble bases,
- alkalis.
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The electrolysis of sodium chloride solution produces hydrogen and chlorine. Sodium hydroxide solution is also produced. These are important reagents for the chemical industry.
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The particular salt produced in any reaction between an acid and a base or alkali depends on:
- the acid used,
- the metal in the base or alkali.
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The state symbols in equations are (s), (l), (g) and (aq).
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to complete and balance supplied half equations for the reactions occurring at the electrodes during electrolysis.
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to explain and evaluate processes that use the principles described in this unit
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to predict the products of electrolysing solutions of ions
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to suggest methods to make a named salt
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When an ionic substance is melted or dissolved in water, the ions are free to move about within the liquid or solution.
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II. Additional materials
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AQA GCSE Biology (4411)
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II. Biology 1
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1.How do human bodies respond to changes inside them and to their
environment?
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Hormones regulate the functions of many organs and cells. E.g., the monthly release of an egg from a woman’s ovaries and the changes in the thickness of the lining of her womb are controlled by hormones secreted by: the pituitary gland and the ovaries
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Information from receptors passes along cells (neurones) in nerves to the brain. The brain coordinates the response.
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Internal conditions which are controlled include:
- the water content of the body,
- the ion content of the body,
- temperature,
- blood sugar levels.
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Many processes within the body are coordinated by chemical substances called hormones. Hormones are secreted by glands and are transported to their target organs by the bloodstream.
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Receptors detect stimuli which include light, sound, changes in position, chemicals, touch, pressure, pain and temperature. (The structure and functions of sense organs such as the eye and the ear are not required.)
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Reflex actions are automatic and rapid. They often involve sensory, relay and motor neurones.
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Several hormones are involved in the menstrual cycle of a woman. Those hormones involved in promoting the release of an egg include: FSH and Oestrogen.
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The nervous system enables humans to react to their surroundings and coordinate their behaviour.
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The role of receptors, sensory neurones, motor neurones, relay neurones, synapses and effectors in simple reflex actions.
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The uses of hormones in controlling fertility include: - giving oral contraceptives which contain hormones to inhibit FSH production, - giving FSH as a ‘fertility drug’ to a woman whose level of FSH is too low (stimulate eggs to mature).
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to evaluate the benefits of, and the problems that may arise from, the use of hormones to control fertility, including IVF
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to evaluate the claims of manufacturers about sports drinks.
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2. What can we do to keep our bodies healthy?
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3. How do we use/abuse medical and recreational drugs?
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4. What causes infectious diseases and how can our bodies defend themselves against them?
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5. What determines where particular species live and how many of them there are?
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6. Why are individuals of the same species different from each other? What new methods do we have for producing plants and animals with the characteristics we prefer?
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7. Why have some species of plants and animals died out?
How do new species of plantsand animals develop?
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8. How do humans affect the environment?
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Carbon dioxide and methane in the atmosphere absorb most of the energy radiated by the Earth. Some of this energy is re-radiated back to the Earth and so keeps the Earth warmer. Increasing levels of these gases may be causing global warming.
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Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste.
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Improving the quality of life without compromising future generations is known as sustainable development. Planning is needed at local, regional and global levels to manage sustainability.
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Increases in the numbers of cattle and rice fields have increased the amount of methane released into the atmosphere.
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Large scale deforestation in tropical areas has:
- increased the release of carbon dioxide into the atmosphere,
- reduced the rate at which carbon dioxide is removed from the atmosphere and ‘locked-up’ for many years as wood.
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Living organisms can be used as indicators of pollution:
- lichens can be used as air pollution indicators
- invertebrate animals can be used as water pollution indicators.
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Loss of forest leads to reduction in biodiversity. Some of the organisms that are lost may have been of future use.
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More waste is being produced which, unless properly handled, may pollute:
- water,
- air,
- land.
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Rapid growth in the human population and an increase in the standard of living means that:
- raw materials, are rapidly being used up
- more waste is produced
- pollution will be caused.
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to analyse and interpret scientific data concerning environmental issues
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to evaluate methods used to collect environmental data and consider their validity and reliability as evidence for environmental change.
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to weigh evidence and form balanced judgements about some of the major environmental issues facing society, including the importance of sustainable development
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III.Biology 2
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III.Biology 3
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1. How do dissolved materials get into and out of animals and plants?
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2. How are dissolved materials transported around the body?
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3. How does exercise affect the exchanges taking place within the body?
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4. How do exchanges in the kidney help us to maintain the internal environment in mammals and how has biology helped us to treat kidney disease?
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5. How are microorganisms used to make food and drink?
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6. What other useful substances can we make using microorganisms?
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Ethanol-based fuels can be produced by the anaerobic fermentation of sugar cane juices and from glucose derived from maize starch by the action of carbohydrase. The ethanol is
distilled from the products of the fermentation.
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Fuels can be made from natural products by fermentation. Biogas, mainly methane, can be produced by anaerobic fermentation of a wide range of plant products or waste material containing carbohydrates.
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Microorganisms can be grown in large vessels called fermenters to produce useful products such as antibiotics. Industrial fermenters usually have:
- an air supply,
- a stirrer,
- a water-cooled jacket,
- instruments.
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On a large scale, waste from, for example, sugar factories or sewage works can be used. On a small scale, biogas generators can be used to supply the energy needs of individual families or farms.
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The antibiotic, penicillin, is made by growing the mould Penicillium, in a fermenter. The medium contains sugar and other nutrients eg a source of nitrogen. The Penicillium only starts to make penicillin after using up most of the nutrients for growth.
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The fungus Fusarium is used to make mycoprotein, a protein-rich food suitable for vegetarians. The fungus is grown on starch in aerobic conditions and the biomass is harvested and purified.
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to evaluate the advantages and disadvantages of given designs of biogas generator.
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to interpret economic and environmental data relating to production of fuels by fermentation and their use
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7. How can we be sure we are using microorganisms safely?
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IV.Biology
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AQA GCSE Chemistry (4421)
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I. Chemistry 1
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10. How do rocks provide building materials?
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All substances are made of atoms. A substance that is made of only one sort of atom is called an element. There are about 100 different elements. Elements are shown in the periodic table. The groups contain elements with similar properties.
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Atoms and symbols are used to represent and explain what is happening to the substances in chemical reactions.
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Atoms have a small central nucleus around which there are electrons.
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Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium.
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Calcium carbonate can be decomposed by heating (thermal decomposition) to make calcium oxide (quicklime) and carbon dioxide.
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Carbonates of other metals decompose on heating in a similar way.
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Limestone and its products have many uses, including slaked lime, mortar, cement, concrete and glass.
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Limestone, containing the compound calcium carbonate (CaCO3), is quarried and can be used as a building material.
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No atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants and we can write balanced equations showing the atoms involved.
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Quicklime (calcium oxide) reacts with water to produce slaked lime (calcium hydroxide).
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The formula of a compound shows the number and type of atoms that are joined together to make the compound.
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to consider and evaluate the environmental, social and economic effects of exploiting limestone and producing building materials from it
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to evaluate the developments in using limestone, cement, concrete and glass as building materials, and their advantages and disadvantages over other materials.
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When elements react, their atoms join with other atoms to form compounds. This involves giving, taking or sharing electrons and the atoms are held together by chemical bonds.
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11. How do rocks provide metals and how are metals use
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12. How do we get fuels from crude oil?
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A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.
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Alkane molecules can be represented in the forms of molecular formula and structural formula.
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Crude oil is a mixture of a very large number of compounds.
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Most fuels contain carbon and/or hydrogen and may also contain some sulfur. The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide and sulfur dioxide. Particles may also be released.
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Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only (hydrocarbons). Most of these are saturated hydrocarbons called alkanes, which have the general formula CnH2n+2
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Some properties of hydrocarbons depend on the size of their
molecules. These properties influence how hydrocarbons are used
as fuels.
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Sulfur can be removed from fuels before they are burned, for example in vehicles. Sulfur dioxide can be removed from the waste gases after combustion, for example in power stations.
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Sulfur dioxide causes acid rain, carbon dioxide causes global warming, and particles cause global dimming.
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The many hydrocarbons in crude oil may be separated into fractions, each of which contains molecules with a similar number of carbon atoms. This process is fractional distillation.
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to consider and evaluate the social, economic and environmental impacts of the uses of fuels
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to evaluate developments in the production and uses of better fuels, for example ethanol and hydrogen.
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to evaluate the impact on the environment of burning hydrocarbon fuels
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13. How are polymers and ethanol made from oil?
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Alkenes can be used to make polymers such as poly(ethene) and poly(propene). In these reactions, many small molecules (monomers) join together to form very large molecules (polymers).
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Ethene can be reacted with steam in the presence of a catalyst to produce ethanol.
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Hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules. This process involves heating the hydrocarbons to vaporise them and passing the vapours over a hot catalyst. A thermal decomposition reaction then occurs.
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Many polymers are not biodegradable, so they are not broken down by microorganisms and this can lead to problems with waste disposal.
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Polymers have many useful applications and new uses are being developed, for example: new packaging materials, waterproof coatings for fabrics, dental polymers, wound dressings, hydrogels,
smart materials, including shape memory polymers.
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Polymers have properties that depend on what they are made from and the conditions under which they are made. For example, slime with different viscosities can be made from poly(ethenol).
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Some of the products of cracking are useful as fuels.
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The products of cracking include alkanes and unsaturated hydrocarbons called alkenes. Alkenes have the general formula CnH2n
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to evaluate the advantages and disadvantages of making ethanol from renewable and non-renewable sources.
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to evaluate the social and economic advantages and disadvantages of using products from crude oil as fuels or as raw materials for plastic and other chemicals
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to evaluate the social, economic and environmental impacts of the uses, disposal and recycling of polymers
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Unsaturated hydrocarbon molecules can be represented in the forms of molecular formula and structural formula.
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14. How can plant oils be used?
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15. What are the changes in the Earth and its atmosphere?
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II. Chemistry 2
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16. How do sub-atomic particles help us to understand the structure of substances?
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All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of protons.
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An ionic compound is a giant structure of ions. Ionic compounds are held together by strong forces of attraction between oppositely charged ions. These forces act in all directions in the
lattice and this is called ionic bonding.
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Atoms have a small central nucleus made up of protons and neutrons around which there are electrons.
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Chemical bonding involves either transferring or sharing electrons in the highest occupied energy levels (shells) of atoms.
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Compounds are substances in which atoms of two, or more, elements are not just mixed together but chemically combined.
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Electrons occupy particular energy levels. Each electron in an atom is at a particular energy level (in a particular shell). The electrons in an atom occupy the lowest available energy levels (innermost available shells).
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Elements in the same group in the periodic table have the same number of electrons in the highest energy levels (outer electrons).
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In an atom, the number of electrons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge.
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Metals consist of giant structures of atoms arranged in a regular pattern. The electrons in the highest occupied energy levels (outer shell) of metal atoms are delocalised and so free to move through the whole structure.
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The elements in Group 1 of the periodic table, the alkali metals, have similar chemical properties. They all react with non-metal elements to form ionic compounds in which the metal ion has a
single positive charge.
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The elements in Group 7 of the periodic table, the halogens, have similar chemical properties. They react with the alkali metals to form ionic compounds in which the halide ions have a single
negative charge.
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The number of protons in an atom is called its atomic number (proton number). Atoms are arranged in the modern periodic table in order of their atomic number (proton number).
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The relative electrical charges: proton = +1, neutron = 0 and electron = –1.
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to represent the bonding in metals in the following form: schematic representation of the shell structure of atoms in metals or model of crystal lattice of metals.
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to represent the covalent bonds in molecules such as water, ammonia, hydrogen, hydrogen chloride, chlorine, methane and oxygen and in giant structures such as diamond and silicon dioxide.
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to represent the electronic structure of the first twenty elements of the periodic table in the following forms: schematic representation of the shell structure and number of electrons placed in each shell.
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to represent the electronic structure of the ions in sodium chloride, magnesium oxide and calcium chloride in the following forms: schematic representation of the shell structure and number of electrons placed in each shell.
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to write balanced chemical equations for reactions.
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When atoms form chemical bonds by transferring electrons, they form ions. Atoms that lose electrons become positively charged ions. Atoms that gain electrons become negatively charged ions.
Ions have the electronic structure of a noble gas (Group 0).
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When atoms share pairs of electrons, they form covalent bonds. Some covalently bonded substances consist of simple molecules such as H2, Cl2, O2, HCl, H2O and CH4 . Others have giant covalent structures such as diamond and silicon dioxide.
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17. How do structures influence the properties and uses of substances?
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Atoms that share electrons can also form giant structures or macromolecules. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures (lattices) of atoms.
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In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard.
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In graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other and so graphite is soft and slippery.
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In graphite, one electron from each carbon atom is delocalised. These delocalised electrons allow graphite to conduct heat and electricity.
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Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces in all directions between oppositely charged ions. These compounds have high
melting points and high boiling points.
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Metals conduct heat and electricity because of the delocalised electrons in their structures.
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Nanoscience refers to structures that are 1-100 nm in size, of the order of a few hundred atoms. Nanoparticles show different properties to the same materials in bulk, which may lead to the development of new computers, new catalysts, new coatings.
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Substances that consist of simple molecules are gases, liquids or solids that have relatively low melting points and boiling points.
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Substances that consist of simple molecules do not conduct electricity because the molecules do not have an overall electric charge.
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Substances that consist of simple molecules have only weak forces between the molecules (intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds,
when the substance melts or boils.
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The layers of atoms in metals are able to slide over each other and so metals can be bent and shaped.
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to evaluate developments and applications of new materials, eg nanomaterials, smart materials.
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to relate the properties of substances to their uses
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to suggest the type of structure of a substance given its properties
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When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and carry the current.
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18. How much can we make and how much do we need to use?
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Although reversible reactions may not go to completion, they can still be used efficiently in continuous industrial processes, such as the Haber process that is used to manufacture ammonia.
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Atoms can be represented as shown: Mass number 23, Na, Atomic Number 11
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Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element.
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Even though no atoms are gained or lost in a chemical reaction, it is not always possible to obtain the calculated amount of a product.
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In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called reversible reactions and are represented by reaction equation with double arrow.
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On cooling, the ammonia liquefies and is removed. The remaining hydrogen and nitrogen is re-cycled.
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The amount of a product obtained is known as the yield. When compared with the maximum theoretical amount as a percentage, it is called the percentage yield.
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The atom economy (atom utilisation) is a measure of the amount of starting materials that end up as useful products. It is important for sustainable development and for economical reasons to use reactions with high atom economy.
-
The masses of reactants and products can be calculated from balanced symbol equations.
-
The percentage of an element in a compound can be calculated from the relative mass of the element in the formula and the relative formula mass of the compound.
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The purified gases are passed over a catalyst of iron at a high temperature (about 450 °C) and a high pressure (about 200 atmospheres). Some of the hydrogen and nitrogen reacts to form ammonia.
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The raw materials for the Haber process are nitrogen and hydrogen. Nitrogen is obtained from the air and hydrogen may be obtained from natural gas or other sources.
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The reaction conditions are chosen to produce a reasonable yield of ammonia quickly.
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The relative amounts of all the reacting substances at equilibrium depend on the conditions of the reaction.
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The relative atomic mass of an element (Ar) compares the mass of atoms of the element with the 12C isotope. It is an average value for the isotopes of the element.
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The relative formula mass (Mr) of a compound is the sum of the relative atomic masses of the atoms in the numbers shown in the formula.
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The relative formula mass of a substance, in grams, is known as one mole of that substance.
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The relative masses of protons, neutrons and electrons: proton = 1, neutron = 1, electron = very smal l
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The total number of protons and neutrons in an atom is called its mass number.
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to calculate chemical quantities involving empirical formulae, reacting masses and percentage yield
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to calculate chemical quantities involving formula mass (Mr) and percentages of elements in compounds
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to calculate the atom economy for industrial processes and be able to evaluate sustainable development issues related to this economy.
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to explain and evaluate the development, advantages and disadvantages of using catalysts in industrial processes.
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When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction.
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19. How can we control the rates of chemical reactions?
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20. Do chemical reactions always release energy?
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An endothermic reaction is one that takes in energy, often as heat, from the surroundings. Endothermic reactions include thermal decompositions.
-
An exothermic reaction is one that transfers energy, often as heat, to the surroundings. Examples of exothermic reactions include combustion, many oxidation reactions and neutralisation.
-
If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction. The same amount of energy is transferred in each case.
-
If the temperature is raised, the yield from the endothermic reaction increases and the yield from the exothermic reaction decreases.
-
In gaseous reactions, an increase in pressure will favour the reaction that produces the least number of molecules as shown by the symbol equation for that reaction.
-
It is important for sustainable development as well as economic reasons to minimise energy requirements and energy wasted in industrial processes. Non-vigorous conditions mean less energy is used and less is released into the environment.
-
The relative amounts of all the reacting substances at equilibrium depend on the conditions of the reaction.
-
These factors, together with reaction rates, are important when determining the optimum conditions in industrial processes, including the Haber process.
-
to describe the effects of changing the conditions of temperature and pressure on a given reaction or process
-
to evaluate the conditions used in industrial processes in terms of energy requirements.
-
When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction.
-
When chemical reactions occur, energy is transferred to or from the surroundings.
-
21. How can we use ions in solutions?
-
Ammonia dissolves in water to produce an alkaline solution. It is used to produce ammonium salts. Ammonium salts are important as fertilisers.
-
At the negative electrode, positively charged ions gain electrons (reduction) and at the positive electrode, negatively charged ions lose electrons (oxidation).
-
Copper can be purified by electrolysis using a positive electrode made of the impure copper and a negative electrode of pure copper in a solution containing copper ions.
-
During electrolysis, positively charged ions move to the negative electrode, and negatively charged ions move to the positive electrode.
-
Hydrogen ions H+(aq) make solutions acidic and hydroxide ions OH– (aq) make solutions alkaline. The pH scale is a measure of the acidity or alkalinity of a solution.
-
If there is a mixture of ions, the products formed depend on the reactivity of the elements involved.
-
In neutralisation reactions, hydrogen ions react with hydroxide ions to produce water. This reaction can be represented by the equation: H+(aq) + OH– (aq) → H2O(l).
-
Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. Precipitation can be used to remove unwanted ions from solutions, for example in treating water for drinking or in treating effluent.
-
Metal oxides and hydroxides are bases. Soluble hydroxides are called alkalis.
-
Passing an electric current through ionic substances that are molten or in solution breaks them down into elements. This process is called electrolysis.
-
Reactions at electrodes can be represented by half equations, for example: 2Cl– → Cl2 + 2e–
-
Salt solutions can be crystallised to produce solid salt.
-
Soluble salts can be made from acids by reacting them with: − metals - not all metals are suitable, − insoluble bases – the base is added to the acid − alkalis - an indicator can be used.
-
The electrolysis of sodium chloride solution produces hydrogen and chlorine. Sodium hydroxide solution is also produced. These are important reagents for the chemical industry.
-
The particular salt produced in any reaction between an acid and a base or alkali depends on:
− the acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates)
− the metal in the base or alkali.
-
The state symbols in equations are (s), (l), (g) and (aq).
-
to complete and balance supplied half equations for the reactions occurring at the electrodes during electrolysis.
-
to explain and evaluate processes that use the principles described in this unit
-
to predict the products of electrolysing solutions of ions
-
to suggest methods to make a named salt
-
When an ionic substance is melted or dissolved in water, the ions are free to move about within the liquid or solution.
-
III. Chemistry 3
-
22. How was the periodic table developed and how can it help us understand the reactions of elements?
-
A more reactive halogen can displace a less reactive halogen from
an aqueous solution of its salt.
-
Compared with the elements in Group 1, transition elements:
− have higher melting points (except for mercury) and higher
densities
− are stronger and harder
− are much less reactive and so do not react as vigorously with
water or oxygen.
-
In Group 1, the further down the group an element is:
− the more reactive the element
− the lower its melting point and boiling point.
-
In Group 7, the further down the group an element is:
− the less reactive the element
− the higher its melting point and boiling point.
-
In the periodic table between Groups 2 and 3 is a block of
elements known as the transition elements. These elements are all
metals.
-
Many transition elements have ions with different charges, form
coloured compounds and are useful as catalysts.
-
Newlands, and then Mendeleev, attempted to classify the elements by arranging them in order of their atomic weights. The list can be arranged in a table, The table is called a periodic table.
-
The early periodic tables were incomplete and some elements were placed in inappropriate Groups if the strict order of atomic
weights was followed. Mendeleev overcame some of the problems.
-
The elements in Group 1 of the periodic table: − are metals with low density − react with non-metals − react with water releasing hydrogen − form hydroxides which dissolve in water to give alkaline solutions.
-
The elements in Group 7 of the periodic table (known as halogens): − have coloured vapours − consist of molecules which are made up of pairs of atoms − form ionic salts − form molecular compounds with other non-metallic elements.
-
The modern periodic table can be seen as an arrangement of the
elements in terms of their electronic structures. Elements in the
same Group have the same number of electrons in their highest
occupied energy level (outer sh
-
The transition elements have similar properties and some special properties because a lower energy level (inner shell) is being filled
in the atoms of the elements between Groups 2 and 3.
-
The trends in reactivity within Groups in the periodic table can be
explained because the higher the energy level:
− the more easily electrons are lost
− the less easily electrons are gained.
-
to explain how attempts to classify elements in a systematic way,
including those of Newlands and Mendeleev, have led through
the growth of chemical knowledge to the modern periodic table
-
to explain why scientists regarded a periodic table of the elements
first as a curiosity, then as a useful tool and finally as an important
summary of the structure of atoms.
-
When electrons, protons and neutrons were discovered early in
the 20th century, the periodic table was arranged in order of
atomic (proton) numbers. When this was done, all elements were
placed in appropriate groups.
-
23. What are strong and weak acids and alkalis? How can we find the amounts of acids and alkalis in solutions?
-
24. What is in the water we drink?
-
25. How much energy is involved in chemical reactions?
-
26. How do we identify and analyse substances?
-
Aluminium, calcium and magnesium ions form white precipitates with sodium hydroxide solution but only the aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution. Copper(II), iron(II) and iron(III) ions form coloured precipitates.
-
Ammonium ions react with sodium hydroxide solution to form
ammonia.
Ammonia gas turns damp litmus paper blue.
-
Carbonates react with dilute acids to form carbon dioxide.
Carbon dioxide turns limewater milky.
-
Copper carbonate and zinc carbonate decompose on heating and
can be identified by the distinctive colour changes.
-
Elements and compounds can be detected and identified using a variety of instrumental methods. Instrumental methods are accurate, sensitive and rapid and are particularly useful when the amount of a sample is very small.
-
Flame tests can be used to identify metal ions. Lithium, sodium,
potassium, calcium and barium compounds produce distinctive
colours in flame tests.
-
Halide ions in solution produce precipitates with silver nitrate
solution in the presence of dilute nitric acid. Silver chloride is
white, silver bromide is cream and silver iodide is yellow.
-
Nitrate ions are reduced by aluminium powder in the presence of sodium hydroxide solution to form ammonia.
-
Organic compounds burn or char when heated in air.
-
Some instrumental methods are suited to identifying elements, such as atomic absorption spectroscopy used in the steel industry. Some methods can be adapted for elements or compounds, such
as mass spectrometry.
-
Sulfate ions in solution produce a white precipitate with barium
chloride solution in the presence of dilute hydrochloric acid.
-
The development of modern instrumental methods has been
aided by the rapid progress in technologies such as electronics
and computing.
-
The empirical formula of an organic compound can be found
from the masses of the products formed when a known mass of
the compound is burned.
-
to evaluate the advantages and disadvantages of instrumental
methods of analysis and the features that influence that
development
-
to interpret and evaluate the results of instrumental analyses
carried out to identify elements and compounds for forensic,
health or environmental purposes.
-
to interpret results of the chemical tests in this specification
-
Unsaturated organic compounds containing double carbon carbon bonds decolourise bromine water.
-
IV. Chemistry
-
AQA GCSE Mathematics A (4301)
-
AQA GCSE Physics (4451)
-
I. Physics 2
-
1. How can we describe the way things move?
-
10. What are nuclear fission and nuclear fusion?
-
2. How do we make things speed up or slow down?
-
3. What happens to the movement energy when things speed up or slow down?
-
4. What is momentum?
-
5. What is static electricity, how can it be used and what is the connection between static electricity and electric currents?
-
6. What does the current through an electrical circuit depend on?
-
7. What is mains electricity and how can it be used safely?
-
8. Why do we need to know the power of electrical appliances?
-
Electric current is the rate of flow of charge.
-
Energy transformed, potential difference and charge are related by the equation:
ergy transformed (joule, J) = potential difference (volt, V) × charge (coulomb, C)
-
Power, potential difference and current are related by the equation: power (watt, W) = current (ampere, A) × potential difference (volt, V)
-
The amount of electrical charge that flows is related to current and time by the equation:
charge (coulomb, C) = current (ampere, A) × time (second, s)
-
The rate at which energy is transformed in a device is called the power. power (watt, W) = energy transformed (joule, J) /
time (second, s)
-
to calculate the current through an appliance from its power and the potential difference of the supply and from this determine the size of fuse needed.
-
When an electrical charge flows through a resistor, electrical energy is transformed into heat energy.
-
9. What happens to radioactive substances when they decay?
-
II. Additional materials
-
AQA GCSE Physics (4451)
-
I. How Science Works
-
II. Physics 1
-
III. Physics 1a
-
IV. Physics 1b
-
14. What are the uses and hazards of the waves that form the electromagnetic spectrum?
-
All types of electromagnetic waves travel at the same speed
through a vacuum (space).
-
Communication signals may be analogue (continuously varying) or
digital (discrete values only, generally on and off). Digital signals
are less prone to interference than analogue and can be easily
processed by computers.
-
Different wavelengths of electromagnetic radiation are reflected,
absorbed or transmitted differently by different substances and
types of surface.
-
Different wavelengths of electromagnetic radiation have different effects on living cells. These effects depend on the type of radiation and the size of the dose.
-
Electromagnetic radiation travels as waves and moves energy from
one place to another.
-
Electromagnetic waves obey the wave formula:
wave speed = frequency × wavelength
(metre/second, m/s) (hertz, Hz) (metre, m)
-
Infra red and visible light can be used to send signals along optical
fibres and so travel in curved paths.
-
Microwaves can pass through the Earth’s atmosphere and are
used to send information to and from satellites and within mobile
phone networks.
-
Radio waves, microwaves, infra red and visible light can be used
for communication.
-
The electromagnetic spectrum is continuous but the wavelengths
within it can be grouped into types of increasing wavelength and
decreasing frequency:
− gamma rays, X-rays, ultraviolet rays, visible light, infra red rays,
microwaves and radio waves.
-
The uses and the hazards associated with the use of each type of
radiation in the electromagnetic spectrum.
-
to evaluate methods to reduce exposure to different types of
electromagnetic radiation.
-
to evaluate the possible hazards associated with the use of
different types of electromagnetic radiation
-
When radiation is absorbed the energy it carries makes the
substance which absorbs it hotter and may create an alternating
current with the same frequency as the radiation itself.
-
15. What are the uses and dangers of emissions from radioactive substances?
-
16. What do we know about the origins of the Universe and how it continues to change?
-
V. Physics 2
-
17. How can we describe the way things move?
-
18. How do we make things speed up or slow down?
-
A body falling through a fluid will initially accelerate due to the
force of gravity. Eventually the resultant force on the body will be
zero and it will fall at its terminal velocity.
-
A driver’s reaction time can be affected by tiredness, drugs and
alcohol.
-
A number of forces acting on a body may be replaced by a single
force which has the same effect on the body as the original forces
all acting together. The force is called the resultant force.
-
A vehicle’s braking distance can be affected by adverse road and
weather conditions and poor condition of the vehicle.
-
Force, mass and acceleration are related by the equation: resultant force (newton, N) = mass (kilogram, kg) x acceleration (metre/second2, m/s2)
-
If the resultant force acting on a moving body is not zero the
body will accelerate in the direction of the resultant force.
-
If the resultant force acting on a moving body is zero the body
will continue to move at the same speed and in the same direction.
-
If the resultant force acting on a stationary body is not zero the
body will accelerate in the direction of the resultant force.
-
If the resultant force acting on a stationary body is zero the body
will remain stationary.
-
The faster a body moves through a fluid the greater the frictional
force which acts on it.
-
The greater the speed of a vehicle the greater the braking force
needed to stop it in a certain distance.
-
The stopping distance of a vehicle depends on the distance the
vehicle travels during the driver’s reaction time and the distance it
travels under the braking force.
-
to calculate the weight of a body using: weight (newton, N) = mass (kilogram, kg) x gravitational field strength (newton/kilogram, N/kg)
-
to draw and interpret velocity-time graphs for bodies that reach
terminal velocity, including a consideration of the forces acting on
the body
-
When a vehicle travels at a steady speed the frictional forces
balance the driving force.
-
Whenever two bodies interact, the forces they exert on each other
are equal and opposite.
-
19. What happens to the movement energy when things speed up or slow down?
-
20. What is momentum?
-
Force, change in momentum and time taken for the change are related by the equation: force (newton, N) = change in momentum (kilogram metre/second, kg(m/s)) / time taken for the change (second, s)
-
Momentum has both magnitude and direction.
-
Momentum is conserved in any collision/explosion provided no
external forces act on the colliding/exploding bodies.
-
Momentum, mass and velocity are related by the equation: momentum (kilogram metre/second, kg m/s) = mass (kilogram, kg) x velocity (metre/second, m/s)
-
to use the conservation of momentum (in one dimension) to
calculate the mass, velocity or momentum of a body involved in a
collision or explosion
-
to use the ideas of momentum to explain safety features.
-
When a force acts on a body that is moving, or able to move, a
change in momentum occurs.
-
21. What is static electricity, how can it be used and what is the connection between static electricity and electric currents?
-
22. What does the current through an electrical circuit depend on?
-
23. What is mains electricity and how can it be used safely?
-
24. Why do we need to know the power of electrical appliances?
-
Electric current is the rate of flow of charge.
-
Energy transformed, potential difference and charge are related by
the equation: energy transformed (joule, J) = potential difference (volt, V) x × charge
(joule, J) (volt, V) (coulomb, C)
-
Power, potential difference and current are related by the
equation: power (watt, W) = current (ampere, A) x potential difference (volt, V)
-
The amount of electrical charge that flows is related to current
and time by the equation: charge (coulomb, C) = current (ampere, A) x time (second, s)
-
The rate at which energy is transformed in a device is called the power. power (watt, W) = energy transformed (joule, J) / time (second, s)
-
to calculate the current through an appliance from its power and
the potential difference of the supply and from this determine the
size of fuse needed.
-
When an electrical charge flows through a resistor, electrical
energy is transformed into heat energy.
-
25. What happens to radioactive substances when they decay?
-
26. What are nuclear fission and nuclear fusion?
-
VI. Physics 3
-
VII. Additional materials
-
AQA GCSE Science A (4461) Biology
-
I. Biology 1a – Human Biology
-
1. How do human bodies respond to changes inside them and to their environment?
-
Hormones regulate the functions of many organs and cells.
-
Information from receptors passes along cells (neurones) in nerves to the brain. The brain coordinates the response.
-
Internal conditions which are controlled include:
- the water content of the body
- the ion content of the body
- temperature
- blood sugar levels
-
Many processes within the body are coordinated by chemical substances called hormones. Hormones are secreted by glands and are transported to their target organs by the bloodstream.
-
Receptors detect stimuli which include light, sound, changes in position, chemicals, touch, pressure, pain and temperature. (The structure and functions of sense organs such as the eye and the ear are not required.)
-
Reflex actions are automatic and rapid. They often involve sensory, relay and motor neurones.
-
Several hormones are involved in the menstrual cycle of a woman. Those hormones involved in promoting the release of an egg include: FSH and Oestrogen.
-
The nervous system enables humans to react to their surroundings and coordinate their behaviour.
-
The role of receptors, sensory neurones, motor neurones, relay neurones, synapses and effectors in simple reflex actions.
-
The uses of hormones in controlling fertility include:
- giving oral contraceptives which contain hormones to inhibit
FSH production,
- giving FSH as a ‘fertility drug’ to a woman whose own level of
FSH is too low to stimulate eggs to mature.
-
to evaluate the benefits of, and the problems that may arise from, the use of hormones to control fertility, including IVF
-
to evaluate the claims of manufacturers about sports drinks.
-
2. What can we do to keep our bodies healthy?
-
3. How do we use/abuse medical and recreational drugs?
-
4. What causes infectious diseases and how can our bodies defend themselves against them?
-
II. Unit Biology 1b – Evolution and Environment
-
III. Additional materials
-
AQA GCSE Science A (4461) Chemistry
-
I. Chemistry 1a – Products from Rocks
-
1. How do rocks provide building materials?
-
All substances are made of atoms. A substance that is made of only one sort of atom is called an element. There are about 100 different elements. Elements are shown in the periodic table. The groups contain elements with similar properties.
-
Atoms and symbols are used to represent and explain what is happening to the substances in chemical reactions.
-
Atoms have a small central nucleus around which there are electrons.
-
Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium.
-
Calcium carbonate can be decomposed by heating (thermal decomposition) to make calcium oxide (quicklime) and carbon dioxide.
-
Carbonates of other metals decompose on heating in a similar way.
-
Limestone and its products have many uses, including slaked lime, mortar, cement, concrete and glass.
-
Limestone, containing the compound calcium carbonate (CaCO3), is quarried and can be used as a building material.
-
No atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants and we can write balanced equations showing the atoms involved.
-
Quicklime (calcium oxide) reacts with water to produce slaked lime (calcium hydroxide).
-
The formula of a compound shows the number and type of atoms that are joined together to make the compound.
-
to consider and evaluate the environmental, social and economic effects of exploiting limestone and producing building materials from it
-
to evaluate the developments in using limestone, cement, concrete and glass as building materials, and their advantages and disadvantages over other materials.
-
When elements react, their atoms join with other atoms to form compounds. This involves giving, taking or sharing electrons and the atoms are held together by chemical bonds.
-
2. How do rocks provide metals and how are metals used?
-
Copper has properties that make it useful for electrical wiring and plumbing. Copper can be extracted by electrolysis of solutions containing copper compounds. The supply of copper-rich ores is limited.
-
Iron from the blast furnace contains about 96% iron. The impurities make it brittle and so it has limited uses.
-
Low density and resistance to corrosion make aluminium and titanium useful metals. These metals cannot be extracted from their oxides by reduction with carbon. Current methods of extraction are expensive (many stages, much energy).
-
Many metals in everyday use are alloys. Pure copper, gold, and aluminium are too soft for many uses and so are mixed with small amounts of similar metals to make them harder for veryday use.
-
Metals that are less reactive than carbon can be extracted from their oxides by reduction with carbon, for example iron oxide is reduced in the blast furnace to make iron. (Details of the blast furnace are not required.)
-
Most iron is converted into steels. Steels are alloys since they are mixtures of iron with carbon and other metals. Low carbon steels are easily shaped, high carbon steels are hard, and stainless steels are resistant to corrosion.
-
Ores contain enough metal to make it economical to extract the metal and this changes over time.
-
Removing all of the impurities would produce pure iron. Pure iron has a regular arrangement of atoms, with layers that can slide over each other, and so is soft and easily shaped, but too soft for many uses.
-
Smart alloys can return to their original shape after being deformed.
-
The elements in the central block of the periodic table are known as transition metals. Like other metals they are good conductors of heat and electricity and can be bent or hammered into shape. They are useful as structural materials.
-
to consider and evaluate the social, economic and environmental impacts of exploiting metal ores, of using metals and of recycling metals
-
to evaluate the benefits, drawbacks and risks of using metals as
structural materials and as smart materials
-
to explain how the properties of alloys (but not smart alloys) are related to models of their structures.
-
Unreactive metals such as gold are found in the Earth as the metal itself but most metals are found as compounds that require chemical reactions to extract the metal.
-
We should recycle metals because extracting them uses limited resources and is expensive in terms of energy and effects on the environment.
-
3. How do we get fuels from crude oil?
-
A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged. It is possible to separate the substances in a mixture by physical methods.
-
Alkane molecules can be represented in the following forms:
- C2H6 and strural form
-
Crude oil is a mixture of a very large number of compounds.
-
Most fuels contain carbon and/or hydrogen and may also contain some sulfur. The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide and sulfur dioxide. Particles may also be released.
-
Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only (hydrocarbons). Most of these are saturated hydrocarbons called alkanes, which have the general formula CnH2n+2
-
Some properties of hydrocarbons depend on the size of their molecules. These properties influence how hydrocarbons are used as fuels.
-
Sulfur can be removed from fuels before they are burned, for example in vehicles. Sulfur dioxide can be removed from the waste gases after combustion, for example in power stations.
-
Sulfur dioxide causes acid rain, carbon dioxide causes global warming, and particles cause global dimming.
-
The many hydrocarbons in crude oil may be separated into fractions, each of which contains molecules with a similar number of carbon atoms, by evaporating the oil and allowing it to condense at a nr of different temperatures (fractional distillation).
-
to consider and evaluate the social, economic and environmental impacts of the uses of fuels
-
to evaluate developments in the production and uses of better fuels, for example ethanol and hydrogen.
-
to evaluate the impact on the environment of burning hydrocarbon fuels
-
II. Chemistry 1b – Oils, Earth and Atmosphere
-
1. How are polymers and ethanol made from oil?
-
Alkenes can be used to make polymers such as poly(ethene) and poly(propene). In these reactions, many small molecules
(monomers) join together to form very large molecules
(polymers).
-
Ethene can be reacted with steam in the presence of a catalyst to produce ethanol.
-
Hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules. This process involves heating the hydrocarbons to vaporise them and passing the vapours over a hot catalyst. A thermal decomposition reaction then occurs.
-
Many polymers are not biodegradable, so they are not broken
down by microorganisms and this can lead to problems with
waste disposal.
-
Polymers have many useful applications and new uses are being developed, for example: new packaging materials, waterproof coatings for fabrics, dental polymers, wound dressings, hydrogels, smart materials, including shape memory polymers.
-
Polymers have properties that depend on what they are mad
from and the conditions under which they are made. For
example, slime with different viscosities can be made from
poly(ethenol).
-
Some of the products of cracking are useful as fuels.
-
The products of cracking include alkanes and unsaturated
hydrocarbons called alkenes. Alkenes have the general formula CnH2n
-
to evaluate the advantages and disadvantages of making ethanol from renewable and non-renewable sources.
-
to evaluate the social and economic advantages and disadvantages of using products from crude oil as fuels or as raw materials for plastic and other chemicals
-
to evaluate the social, economic and environmental impacts of the uses, disposal and recycling of polymers
-
Unsaturated hydrocarbon molecules can be represented in the
following forms:
C2H4 and structural form
-
2. How can plant oils be used?
-
3. What are the changes in the Earth and its atmosphere?
-
III. Additional materials
-
AQA GCSE Science A (4461) Physics
-
I. Physics 1a Energy and Electricity
-
1. How is heat (thermal energy) transferred and what factors affect the rate at which heat is transferred?
-
2. What is meant by the efficient use of energy?
-
3. Why are electrical devices so useful?
-
4. How should we generate the electricity we need?
-
Common energy sources include coal, oil and gas, which are burned to produce heat and uranium/plutonium, in which nuclear fission produces heat.
-
Electricity can be produced directly from the Sun’s radiation using solar cells.
-
Energy from renewable energy sources can be used to drive turbines directly.
-
In most power stations an energy source is used to heat water.
The steam produced drives a turbine which is coupled to an electrical generator.
-
In some volcanic areas hot water and steam rise to the surface. The steam can be tapped and used to drive turbines. This is known as geothermal energy.
-
Renewable energy sources used in this way include wind, the rise and fall of water due to waves and tides, and the falling of water in hydroelectric schemes.
-
The advantages and disadvantages of using fossil fuels, nuclear fuels and renewable energy sources to generate electricity (cost of building power stations, the start-up time, the reliability of the energy source, the relative cost of energy).
-
to compare and contrast the particular advantages and disadvantages of using different energy sources to generate electricity.
-
Using different energy resources has different effects on the environment. These effects include the release of substances into
the atmosphere, noise and visual pollution, and the destruction of
wildlife habitats.
-
II. Physics 1b - Radiation and the Universe
-
1. What are the uses and hazards of the waves that
form the electromagnetic spectrum?
-
All types of electromagnetic waves travel at the same speed through a vacuum (space).
-
Communication signals may be analogue (continuously varying) or digital (discrete values only, generally on and off). Digital signals are less prone to interference than analogue and can be easily processed by computers.
-
Different wavelengths of electromagnetic radiation are reflected absorbed or transmitted differently by different substances and types of surface.
-
Different wavelengths of electromagnetic radiation have different effects on living cells. Some radiations mostly pass through soft tissue without being absorbed, some produce heat, some may cause cancerous changes and some may kill cells.
-
Electromagnetic radiation travels as waves and moves energy from one place to another.
-
Electromagnetic waves obey the wave formula:
wave speed = frequency × wavelength
(metre/second, m/s) = (hertz, Hz) × (metre, m)
-
Infra red and visible light can be used to send signals along optical fibres and so travel in curved paths.
-
Microwaves can pass through the Earth’s atmosphere and are used to send information to and from satellites and within mobile phone networks.
-
Radio waves, microwaves, infra red and visible light can be used for communication.
-
The electromagnetic spectrum is continuous but the wavelengths within it can be grouped into types of increasing wavelength and decreasing frequency: gamma rays, X-rays, ultraviolet rays, visible light, infra red rays, microwaves and radio waves.
-
The uses and the hazards associated with the use of each type of radiation in the electromagnetic spectrum.
-
to evaluate methods to reduce exposure to different types of electromagnetic radiation.
-
to evaluate the possible hazards associated with the use of different types of electromagnetic radiation
-
When radiation is absorbed the energy it carries makes the substance which absorbs it hotter and may create an alternating current with the same frequency as the radiation itself.
-
2. What are the uses and dangers of emissions from radioactive substances?
-
3. What do we know about the origins of the Universe and
how it continues to change?
-
III. Additional materials
-
Key Stage 5
|