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170 Cards in this Set
- Front
- Back
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Ionic compounds |
Giant structures of ions |
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Ions |
Electrically charged atoms |
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How ionic compounds are held together |
Strong forces of attraction (electrostatic forces) between oppositely charged ions, that act in all directions |
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Features of ionic compounds |
Have high melting and boiling points |
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Ionic bond |
Occurs between a metal and a non metal. Involves transfer of electrons from one atom to the other Holds oppositely charged ions together in a giant structure of ionic compounds - regular as all ions are packed together neatly |
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What do ionic bonds form |
Electrically charged ions, each of which has a complete outer energy level |
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Charge of atoms that lose electrons |
Positive |
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Charge of atoms that gain electrons |
Negative |
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Name of group one |
Alkali metals |
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Features of alkali metals |
Have one electron in outermost shell |
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Name of group 7 |
The halogens |
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Features of the halogens |
Have seven electrons in their outermost shells |
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Definition of a mixture |
Two or more elements or compounds that are not chemically combined |
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Definition of compound |
Substances in which the atoms of two or more elements are chemically combined |
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Ways atoms form chemical bonds |
Share electrons (covalent bonds) |
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Arrangement of electrons when atoms form chemical bonds |
Each atom gets a complete outer shell |
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Substances that consist of simple molecules |
Gases, liquids and solids that have relatively low melting or boiling points, with no overall charge so they can't conduct electricity. |
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Why do simple molecular compounds have low melting and boiling points? |
They have weak intermolecular forces |
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Intermolecular forces |
Forces between molecules |
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Covalent bond |
A strong bond between non-metal atoms that is formed when pairs of electrons are shared to achieve stable electronic structures |
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Simple covalently bonded structures |
H2, CL2, O2, HCL, H2O and CH4 |
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Giant covalent structures |
Macromolecules (e.g diamond and silicone) |
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Properties of covalently bonded atoms |
Low melting and boiling points |
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Why do covalently bonded atoms have low melting and boiling points |
Because they often form molecules in which there are: |
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Properties of a giant covalent structure |
All the atoms are linked by strong covalent bonds, which means a very high melting point. |
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Structure of diamond |
Form of carbon |
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Structure of graphite |
Giant covalent structure, |
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Why is Diamond so hard? |
Because it has a large number of covalent bonds |
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Why is graphite soft and slippery? |
Because it has layers that can slide past each other |
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Other features of graphite |
Layers held together by weak intermolecular forces, one electron from each carbon atom is delocalised, which allow graphite to conduct heat and electricity. |
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Why is graphite good at conducting heat and electricity? |
Because one electron from each carbon atom is delocalised |
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Structure of silicone dioxide |
Lattice, each oxygen atom joined to two silicone atoms, and each silicone atom joined to four oxygen atoms |
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Lattice |
Giant, rigid, covalent structure |
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Fullerenes |
Molecules formed by carbon, which have different numbers of carbon atoms |
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Fullerene structure |
Based on hexagon rings of carbon atoms |
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Uses of fullerenes |
Used to deliver drugs in the body, in lubricants, as catalysts and in nanotubes for reinforcing materials, e.g, tennis rackets |
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Why can metals be bent and shaped? |
Because the layers of atoms are able to slide over each other |
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Atom |
The smallest particle of a chemical element that can exist. Consists of a nucleus made of protons and neutrons and surrounding rings filled with electrons |
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Structure of metals |
Giant structure in which electrons in the highest energy level can be delocalised, producing a regular arrangement (lattice) of positive ions that are held together by electrons using electrostatic attraction |
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Why can metals conduct heat and electricity? |
They have delocalised electrons that can move around freely |
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Alloy |
Mixture that contains a metal and at least one other element |
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Why are alloys usually stronger and harder than pure metals? |
Because the added element disturbs the regular arrangement of the metal atoms so the layers don't slide over each other so easily |
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Smart alloys |
Remember their shape. They can be deformed but will return to their original shape. |
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Examples of smart alloys |
Flexible spectacle frames |
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Group of materials smart alloys belong to |
Materials that are being developed to meet the demands of modern engineering and manifacturing. These materials respond to changes in their environment |
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Monomer |
A small hydrocarbon molecule containing a double bond |
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Polymer |
A giant, long chained hydrocarbon |
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Properties affecting polymers |
What monomer is used |
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One use of low density poly ethene |
Carrier bags |
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One use of high density poly ethene |
Used to make plastic bottles |
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Thermo softening |
Polymers that consist of individual polymer chains that are tangled together (like spaghetti) |
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Thermo-setting |
Polymers that consist of polymer chains that are joined together by cross links between them. |
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Properties of thermo-softening polymers |
Weak intermolecular forces between all of the polymer chains |
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Properties of thermo-setting polymers |
Contain cross links, so they don't melt when heated |
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Nano science |
Study of very small structures, roughly 1-100 nanometers in size |
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Nanoparticles |
Tiny particles that can combine to form structures called nanostructures |
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Nanometers |
One billionth of a meter |
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Atomic (proton) number |
Number of protons in the atom |
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Equation for number of neutrons |
Number of neutrons = mass number - atomic number |
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Number of electrons in an atom |
Equal to the number of protons, therefore atom has no overall charge |
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Relative mass of proton |
1 |
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Relative mass of neutron |
1 |
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Relative mass of electron |
Very small (negligible) |
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Isotopes |
Atoms of the same element that have different numbers of neutrons. They have the same atomic number but different mass number. |
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Chlorine number of Isotopes |
2 |
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Relative atomic mass |
Number of protons and neutrons in nucleus, usually the larger number on periodic table |
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Relative formula mass of a compound |
Relative atomic masses of all it's elements added together |
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Why are nano particles manipulated? |
So materials can be developed that have new and specific properties |
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Mass of a compound |
Relative formula mass in grams |
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Percentage mass= |
Relative mass of element in the compound (divided by) relative formula mass of compound (x100) |
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Empirical formula of a compound |
The simplest whole number ratio of each kind of atom in the compound |
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Mole |
A measure of the number of particles contained in a substance |
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Particle |
Atoms or molecules |
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Number of particles in one mole of any substance |
6x10 to the power of 23 |
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Number of moles of substance= |
Mass of substance (divided by) mass of one mole |
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If substance is a compound, mass of one mole of substance is always equal to... |
Relative formula mass of the substance in grams |
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Instrumental methods |
Where highly accurate instruments are used to analyse and identify substances |
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Retention time |
Time taken to pass through gas chromatograph |
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Properties of nanoparticles |
Different to the properties of the same material in bulk |
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Gas chromatography linked to mass spectroscopy |
Allows different substances, carried by a gas, to travel through a column packed with solid material at different speeds so they separate out. Each substance produces a separate peak on an output known as a gas chromatograph |
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Chemical analysis |
Can be Used to identify additives in food |
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Chromatography |
Can be used to identify artificial colours, by comparing them to known substances |
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Atoms in a chemical reaction are never... |
Lost or gained |
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Yield |
Amount of product obtained |
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Reasons that calculated amount of product may not be obtained |
Reaction is reversible; may not go to completion |
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Percentage yield = |
Yield from reaction (divided by) maximum theoretical yield (x 100) |
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Reversible reactions |
When products can react to produce original reactants |
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What happens to solid ammonium when heated and what is produced? |
Decomposes, produces ammonia and hydrogen chloride gas |
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Nano particles are sensitive to... |
Light, heat and magnetism |
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Research into nano particles may lead to the development of new... |
Computers |
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Width of human hair |
1x10 to the power of minus 5 |
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Length of virus/small bacteria |
1x10 to the power of minus 7 |
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Length of atoms and small molecules |
1x10 to the power of minus 9 |
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Nanometers |
One billionth of a meter |
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What is produced when ammonia reacts with hydrogen chloride gas? |
Clouds of white ammonium chloride powder |
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Chemical reactions only occur when... |
Particles collide with each other with sufficient energy |
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Activation energy |
The minimum amount of energy required to cause a reaction |
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Four factors that affect the rate of a reaction |
Temperature |
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In a cold reaction mixture the particles... |
Move quite slowly. They collide less often with less energy so fewer collisions are successful. |
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In a hot reaction mixture the particles... |
Move more quickly. They collide more often, with greater energy, so more collisions are successful |
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In a low concentration reaction, the particles are... |
Spread out. They collide less often, so there are fewer successful collisions. |
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In a high concentration reaction, the particles are... |
Crowded close together. They collide more often, so there are more successful collisions. |
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How to increase frequency of collisions in a concentration reaction. |
Increase the pressure of reacting gasses |
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Concentration of solutions given in... |
Moles per cubic decimetre (mol/dm3) |
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Large pieces of solid reactant have a... |
Small surface area in relation to their volume. Fewer particles exposed and available for collisions, which means fewer collisions and a slower reaction. |
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Small pieces of a solid reactant have a... |
Large surface area in relation to their volume, som more particles are exposed and available for collisions. This means more collisions and a faster reaction. |
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Catalyst |
Substance that changes the rate of a chemical reaction without being used up or altered in the process. |
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Different reactions need different catalysts. For example... |
The cracking of hydrocarbons uses broken pottery |
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A catalyst... |
Reduces the amount of energy needed for a successful collision |
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What does increasing the rate of a chemical reaction reduce in industry? |
Costs |
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Rate of reaction= |
Amount of reactant used OR product formed (divided by) time |
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Two ways to find the rate of a chemical reaction |
Measuring the amount of reactants used |
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3 things to remember when plotting reaction rates on a graph. |
1. The steeper the line, the faster the reaction |
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When chemical reactions occur... |
Energy is transferred to, or from the surroundings. |
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Exothermic reactions |
They give out heat to surroundings |
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Examples of exothermic reactions |
Neutralising alkalis with acids |
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Endothermic reactions |
They take in heat from surroundings |
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Examples of endothermic reactions |
Thermal decomposition |
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If a reaction is endothermic in one direction... |
It is exothermic in the opposite direction |
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Aqueous solution |
Produced when a substance is dissolved in water |
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All state symbols |
(S) solid |
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Metals react with dilute acid to form... |
A metal salt and hydrogen |
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Salt |
A word used to describe any metal compound made from a reaction between a metal and an acid |
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Metal reactions with acid |
Silver- no reaction |
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Bases |
Oxides and hydroxides of metals |
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Alkalis |
Soluble bases |
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Oxides and hydroxides of transition metals are... |
Insoluble |
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Preparation of salts of oxide and hydroxide metals |
1. The metal oxide or hydroxide is added to an acid until no more will react |
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Word equation for base salt preparation |
Acid + base = neutral salt solution + water |
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Neutralisation reaction of solutions of hydroxides with a particular acid |
Acid + alkaline hydroxide solution = neutral salt solution + water |
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Precipitate |
Solid substance |
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Insoluble salts made by... |
Mixing appropriate solutions of ions so that a precipitate is formed |
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Precipitation can be used to... |
Remove unwanted ions from a solution. E.g softening hard water. |
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How to soften hard water |
Precipitation, so the calcium ions a precipitated out as insoluble calcium carbonate. |
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Two chemical opposites |
Acids and alkalis |
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Acids contain... |
Hydrogen ions, H+ (aq) |
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Alkalis contain... |
Hydroxide ions, OH- (aq) |
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What happens if acids and alkalis are added together in the correct amounts |
They neutralise each other |
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Word equation for neutralisation reaction |
H+ + OH- = H2O |
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Ph1 is... |
Acidic |
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Ph14 is... |
Alkali |
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Ph7 is... |
Neutral |
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Ammonia |
Alkali gas that dissolves in water to make an alkaline solution |
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Indicators |
Dyes that change colour depending on whether they are in acidic or alkaline solutions |
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What does ammonia neutralise and produce |
Nitric acid to produce ammonium nitrate |
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Nitram |
Nitrate of ammonia |
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Nitrogen-based fertilisers |
Important chemicals that increase the yield of crops |
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Problems nitrates cause if they reach streams, rivers or ground water. |
Upset the natural balance of water |
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Ammonium salts produced by.... |
Ammonium hydroxide neutralised with acids |
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Litmus |
Indicator that changes colour from red to blue or vice versa |
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Universal indicator |
Mixture of dyes that show a range of colours to indicate how acidic or alkali a substance is |
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pH scale |
A measure of the acidity or alkalinity of an aqueous solution |
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What happens when substances dissolve in water? |
They dissociate into their individual ions |
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Electrolysis |
Breaking down of a compound containing ions into its elements using an electrical current |
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Electrolyte |
Substance in electrolysis being broken down |
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Ionic substances |
Chemical compounds that allow a current to pass through when they are molten or dissolved in water |
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During electrolysis |
Negatively charged ions move to the positive electrode and positively charged ions move to the negative electrode |
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Electrode |
A piece of metal or carbon that allows electric current to enter and leave during electrolysis |
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If there is a mixture of ions in a solution, the products formed... |
Depend on the reactivity of the elements involved |
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Redox reaction |
A chemical reaction where both reduction and oxidation occur |
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Reduction |
Positively charged ions gain electrons at the negative electrode |
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Oxidation |
Negatively charged ions lose electrons at the positive electrode |
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Electroplating |
When electrolysis is used to electroplate objects with metals like copper or silver |
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Aluminium is obtained by... |
Electrolysis of aluminium oxide mixed with cryolite. |
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Function of cryolite in extraction of aluminium |
Lowers the melting point of aluminium oxide for cheaper energy costs |
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Sodium chloride |
Common salt |
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Reagents produced from electrolysis of brine |
1.Chlorine gas (at positive electrode) |
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Use of chlorine in industry |
Kill bacteria in drinking water and swimming pools, and to manufacture hydrochloride acid, disinfectants, bleach and PVC |
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How chlorine is detected in a laboratory |
Bleaches damp litmus paper |
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Covalent bonding in elements |
group 7 - need to share one electron and so form a single covalent bonds group 6 - need to share two electrons and so form two covalent bonds group 5 can form three bonds and group 4 can form four bonds |
