C2 Chemistry

Additional Science

Key Recall Questions

*Cover up the answers, ask yourself a question (or get your partner to ask you), if you get it right then tick the chart, wrong put a cross. Keep practising until all columns are ticked!

Key terms

Key Recall Question Answer

1. What is a particle? A general word used by scientists to mean small part of matter (something)

2. What is an atom? The smallest particle that can be recognized as an element. If you break an element into its smaller pieces you can no longer recognize that it is an element.

3. What is an element? A substance that is composed of only one type of atom.

4. What is a mixture? Substances which are together (in the same space) but not chemically joined.

5. What is a compound? Substances in which atoms of two or more elements are chemically combined.

6. What is a molecule? A word to describe atoms which are chemically joined together. These might be two of the same type of atoms (an element molecule) or two or more different types of atom (a compound molecule)

7. What are the reactants of a chemical reaction? The substances which react together in a chemical reaction

8. What are the products of a chemical reaction? The substances which are produced as a result of a chemical reaction

9. Why is it important to show chemical reactions with an arrow?

The arrows shows ‘reacts to make’ and signifies that the reactants have been chemically changed into products and cannot be (easily) reversed

10. What are the four state symbols used in chemical reactions and what do they mean?

Solid (s), Liquid (l), Gas (g) and Aqueous (aq) which means dissolved in water

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C2.1 Structure and bonding_1

Key Recall Question Answer1. What is a compound? Substances in which atoms of two or more

elements are chemically combined.2. What are the two ways chemical bonds achieve the electronic structure of a noble gas?

They transfer or share electrons in the highest occupied energy levels (shells)

3. What do atoms become when they form chemical bonds by transferring electrons?

Ions

4. What charge do ions have when the atom which formed them lost an electron?

Positive (+)

5. What charge do ions have when the atom which formed them gains an electron?

Negative (-)

6. What charge do ions have when they are formed from an element in group 1?

+1

7. What charge do ions have when they are formed from an element in group 7?

-1

8. What charge do ions have when they are formed from an element in group 2?

+2

9. What charge do ions have when they are formed from an element in group 6?

-2

10. Which group of elements do not form ions? Group 0 (noble gases)Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date

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C2.1 Structure and bonding_2

Key Recall Question Answer1. What type of electron structure do ions have? The electron structure of a noble gas2. What are the elements in group 1 known as? Alkali metals3. When they react with non-metals, what charge does the metal ion have in the ionic compound formed?

A single positive charge

4. Can you name any elements in group 1? Lithium, sodium, potassium, rubidium, caesium, francium (it is important that you at least know sodium is a group 1 element)

5. What are the elements in group 7 known as? Halogens6. When they react with alkali metals, what charge does the halide ion have in the ionic compound formed?

A single negative charge

7. Can you name any elements in group 7? Fluorine, chlorine, bromine, iodine, astatine (It is important that you at least know chlorine is a group 7 element)

8. How are ionic compounds formed? Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions.

9. What is an ionic lattice? A structure formed as the result of all the electrostatic forces between ions attracting each other.

10. What is the name of the ionic compound formed when sodium and chlorine form ions?

Sodium chloride

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2.1 Structure and bonding_3

Key Recall Question Answer1. What type of bonding is formed when atoms share electrons?

Covalent

2. How strong are covalent bonds? Very strong3. Can you name seven small covalent molecules and give their formula?

Hydrogen (H2), Chlorine (Cl2), Oxygen (O2), Hydrochloric acid (HCl), Water (H2O), Ammonia (NH3) and Methane (CH4)

4. Can you name three macromolecules which have giant covalent structures?

Diamond, graphite and silicon dioxide.

5. What are the boiling points of small covalent molecules like and why?

They have low melting and boiling points (so are often gases) because the intermolecular forces (forces between molecules, not within) are weak so are easily broken

6. Do simple covalent molecules conduct electricity ad why/why not?

They do not conduct electricity because the molecules do not have an overall electric charge.

7. What is the structure of a metal like? Metals are giant structures of atoms arranged in a regular pattern. They have positive metal ions with electrons between the ions holding them together with strong electrostatic attraction.

8. What is special about the electrons in a metal? They are ‘delocalised’ so are free to move about through the whole structure

9. Name some reactive metals Potassium, sodium, magnesium, etc.10. Name some unreactive metals Gold, platinum, silver

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C2.2 How structure influences properties_1

Key Recall Question Answer1. When a small covalent molecule like water boils, what happens to it?

The weak intermolecular forces are broken (forces between the water molecules).

2. What is a giant ionic lattice? An ionic compound with a regular structure in which there are strong electrostatic forces in all directions between oppositely charged ions

3. What are the melting and boiling points of ionic compounds (lattices) like and why?

They are high because the forces of attraction are strong, and there are many of them, so a great deal of energy is needed to break these bonds.

4. Do most ionic compounds conduct electricity? Only when dissolved or melted as this means the charged ions are free to move and can therefore carry a current

5. Which chemicals are diamond, graphite and silicon dioxide made of?

Diamond (Carbon), Graphite (Carbon) and sulicon dioxide (Sulphur and Oxygen or ‘silica’)

6. What are the melting and boiling points of large covalent molecules like diamond, graphite and silicon dioxide like and why?

They are very high because the covalent bonds between atoms are very strong

7. How are the atoms in diamond arranged and which properties does this mean it has?

One carbon atom is covalently bonded to four other carbon atoms so diamond is very hard.

8. How are the atoms and electrons in graphite arranged and which properties does this mean it has?

One carbon atom is covalently bonded to three other carbon atoms to form layers. This means there are delocalised electrons therefore the layers are free to slide over each other because there are no covalent bonds between them. This means graphite is soft, slippery and able to conduct electricity and heat (unlike diamond).

9. What are fullerenes? Fullerenes are hexagonal rings of carbon atoms.10. What can fullerenes be used for? They can be used for drug delivery into the body, in

lubricants, as catalysts, and in nanotubes for reinforcing materials (e.g. tennis rackets)

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C2.2 How structure influences properties_2

Key Recall Question Answer1. In terms of their structure, why do metals conduct heat and electricity?

Because they have delocalised electrons in their structures.

2. What property do the layers in metals give them? They are able to be bent and shaped.3. What are alloys? Metals which are usually made from two or more

different metals.4. Why are alloys harder than pure metals? Because they have different sized atoms (due to

the two or more different type of metal) so the layers are distorted and find it difficult to slide over each other.

5. Can you name a shape memory alloy and describe what this term means?

Nitinol (used in dental braces), shape memory alloys can return to their original shape.

6. What is a polymer? A substance made up from repeating monomers7. What do the properties of polymers depend on? What they are made from and the conditions

(temperatures, etc.) in which they were made.8. What is the difference between how low density (LD) and high density (HD) poly(ethane) are made?

They are produced using different catalysts and reaction conditions.

9. What are thermosoftening polymers? Polymers which consist of individual, tangled polymer chains. This means they do not have strong intermolecular forces between the chains.

10. What are thermosetting polymers? Polymers which consist of polymer chains with cross links. This means that they have string forces between chains so do not melt.

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C2.2 How structure influences properties_3

Key Recall Question Answer1. How big are nanoparticles? 1-100nm (a few hundred atoms)2. What is the difference between nanoparticles and substances made of the same elements but larger?

They have different properties and have a high surface area to volume ratio.

3. What sorts of new technologies could nanoparticles be used to develop?

New computers, new catalysts, new coatings, highly selective sensors, stronger and lighter construction materials and new cosmetics such as sun tan creams and deodorants.

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C2.3 Atomic structure, analysis and quantitative chemistry_1

Key Recall Question Answer4. What are the names of the three parts of an atom? Proton, neutron and electron5. What can the ‘mass number’ of an element tell us? The number of protons and neutrons6. What can the ‘atomic number’ of an element tell us?

The number of protons

7. What is the relative mass and charge of a proton? 1 and +18. What is the relative mass and charge of a neutron? 1 and 09. What is the relative mass and charge of an electron?

0 and -1

10. What is an isotope? Atoms of the same element which have different numbers of neutrons (e.g. Hydrogen always has 1 proton but can have 1, 2 or 3 neutrons)

C2.3 Atomic structure, analysis and quantitative chemistry_2

Key Recall Question Answer

1. Which isotope is the relative atomic mass of an atom compared to?

Carbon 12 (6 protons and 6 neutrons), 12 is the average value for the isotopes of carbon.

2. What is the relative formula mass of a compound? It is the sum of the relative atomic masses of the atoms shown in the formula.

3. What is the relative formula mass of a substance when given in grams?

1 mole of the substance (which contains 6.02 x 1023

atoms)4. How do you calculate the relative formula mass of carbon dioxide? (C = 12 and O = 16)

Add all the relative atomic masses of all the atoms together; CO2; Carbon = 12 plus Oxygen = 16 plus another Oxygen = 16 (because it is CO2 meaning 1 atom of carbon and 2 atoms of Oxygen) so the relative formula mass is 12 + 16 + 16 = 44

5. Which methods are used to detect elements and compounds and why?

Instrumental methods because they are accurate, rapid and sensitive (think ARS) so can be used to identify elements and compounds in very small samples.

6. How is chemical analysis particularly useful in the food industry?

It can be used to identify additives in food.

7. Which technique is used to identify artificial colours?

Paper chromatography.

8. Which type of method is Gas chromatography linked to mass spectroscopy (GC-MS) an example of?

An instrumental method

9. What does GC-MS allow scientists to do? Separate a mixture of compounds.Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date

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C2.3 Atomic structure, analysis and quantitative chemistry_3

Key Recall Question Answer1. How is the substance to be analysed in GC-MS carried through the equipment?

Using a gas

2. What is the substance to be analysed passed through?

The gas chromatography column packed with a solid material.

3. What happens to the substance as it passes through the column?

Each element or compound within the substance travels through the column at different speeds, so the time taken can be used to help identify the compound.

4. What is the gas chromatography column linked to? A mass spectrometer5. What does the mass spectrometer show? It will give different peaks which show how long

each substance was in the column for (retention time). It will also give the relative molecular mass of each of the compounds separated.

6. What is the name of the peak which shows the molecular mass?

The molecular ion peak

7. If you want to calculate the percentage of a given element in a compound, which two pieces of information do you need?

The relative mass of the element and the relative formula mass of the compound

8. What is the empirical formula? The simplest ratio of elements in a compound9. What information do you need to calculate the empirical formula?

The masses or percentages of elements in a compound.

10. Why is it not always possible to obtain the calculated amount of a product when carrying out an experiment?

1. the reaction may not go to completion because it is reversible.2. some of the product is lost when separated from the reaction mixture.3. Some of the reactants may react in ways different from the expected reaction

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C2.3 Atomic structure, analysis and quantitative chemistry_4

Key Recall Question Answer1. What is another name for the ‘amount’ of product obtained in a chemical reaction?

Yield

2. What is ‘percentage yield’? The amount of product obtained compared with the maximum theoretical amount as a percentage (amount of product obtained/theoretical amount x 100)

3. What is a reversible reaction? When the products of a reaction can react together to produce the original reactants.

4. Give an example of a reaction which is reversible Ammonium chloride ammonia + hydrogen chloride. Hydrated copper sulphate (blue) anhydrous copper sulphate (white) + water

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C2.4 Rates of reaction 1

Key Recall Question Answer5. Which two ways can you measure rates of reaction?

1. Measuring the amount of reaction used in a given amount of time (amount of reactant used/time)2. Measuring the amount of product formed in a given amount of time (amount of product formed/time)

6. Under what circumstances do chemical reactions occur?

When reacting particles collide with each other with sufficient energy.

7. What is the ‘activation energy’ of a reaction? The minimum amount of energy particles must have to react.

8. What are the 5 ways to alter the rate of a reaction Temperature, concentration of reactants in a solution, gas pressure, surface area of solid reactants and presence of catalysts

C2.4 Rates of reaction_2

Key Recall Question Answer1. Why does increasing temperature increase the rate of reaction?

Because it increases the speed of the reacting particles (they have more energy) so they collide more frequently and more energetically.

2. Why does increasing pressure of reacting gases increase the rate of reaction?

Because it increases the frequency of collisions (particles are closer together)

3. Why does increasing the concentration of reactants in solutions increase the rate of reaction?

Because it increases the frequency of collisions (more particles so more likely to collide).

4. Why does increasing the surface area of solid reactants increase the rate of reaction?

Because it increases the frequency of collisions (more particles on the surface available for reactions)

5. How could you increase the surface area of a marble (calcium carbonate) chip?

You could grind it into a powder (if you added up the surface area of each tiny part of the powder this would be greater than surface area the original chip)

6. What is a catalyst? It is a substance which changes the rate of chemical reactions without being used up. Each catalyst is specific to each reaction.

7. Why are catalysts important in industry? They increase the rate of reaction and therefore can reduce costs.

8. Can you give some examples of catalysts? Platinum (in the ignition of hydrogen or the oxidation of ammonia). Manganese(IV) oxide or enzymes in yeast/potato (in the decomposition of hydrogen peroxide), etc.

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C2.5 Exothermic and endothermic reactions

Key Recall Question Answer1. What is an exothermic reaction? A reaction which transfers energy to the

surroundings (energy EXits)2. Can you give three examples of exothermic reactions?

Combustion reactions, many oxidation reactions and neutralisation.

3. Can you name some examples of everyday uses of exothermic reactions?

Self-heating cans (e.g. coffee) and hand warmers.

4. What is an endothermic reaction? A reaction which takes in energy from the surroundings (heat ENters)

5. Can you give an example of an endothermic reaction?

Thermal decompositions

6. Can you name some examples of everyday uses of endothermic reactions?

Sports injury packs.

7. If a reversible reaction is exothermic in one direction will it be exothermic or endothermic in the other direction?

Endothermic

8. Can you name an example of a reversible reaction which is endothermic and exothermic?

Hydrated copper sulphate (blue) anhydrous copper sulphate (white) + water This is endothermic in this direction but the reverse reaction is exothermic.

9. What does soluble mean? Dissolves in a solvent (typically water)10. What does insoluble mean? Does not dissolve in a solvent (typically water)

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C2.6 Acids, bases and salts_1

Key Recall Question Answer1. What are the four state symbols used in chemical reactions?

(s) solid, (l) liquid, (aq) aqueous and (g) gas.

2. What does aqueous mean? Dissolved in water (a solution)3. What three substances can be used to react with acids in order to make a soluble salt?

Metals, insoluble bases, alkalis

4. What is the difference between a base and an alkali?

Bases are insoluble metal hydroxides or oxides and alkalis are soluble hydroxides.

5. Why can you not use all metals when reacting them with acid to make a soluble salt?

Some are too reactive (e.g. sodium) and some are not reactive enough (e.g. gold)

6. How do you make an insoluble salt using an acid and a base?

Add the base to the acid until no more will react then filter the excess (unreacted) solid off.

7. What is used when an acid reacts with an alkali to make a soluble salt in order to detect when the reaction has happened to completion?

An indicator

8. How can you get a solid salt from a salt solution? Crystallise the solutions (allow the water to evaporate leaving behind the salt)

9. Can you suggest how to make sodium chloride? React sodium hydroxide (alkali) with hydrochloric acid (acid) to completion. Use universal indicator to detect a neutral solution which will be green colour. Add charcoal to remove the indicator then filter this away. Crystallise the salt using an evaporating dish and gentle heat.

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C2.6 Acids, bases and salts_2

Key Recall Question Answer1. How do you make an insoluble salt? Mix appropriate amounts of solutions of ions so

that a precipitate is formed.2. How can precipitation be used in industry? To remove unwanted ions from solutions, e.g. in

treating water or effluent.3. What are bases? Metal oxides and hydroxides which are insoluble.4. What are alkalis? Hydroxides which are soluble.5. In a reaction between an acid and a base or alkali, what does the name of the alt produced depend on?

The metal in the base or alkali and the type of acid used.

6. Which type of soluble salt does hydrochloric acid produce when reacted with a base or alkali?

Chlorides.

7. Which type of soluble salt does nitric acid produce when reacted with a base or alkali?

Nitrates.

8. Which type of soluble salt does sulphuric acid produce when reacted with a base or alkali?

Sulphates.

9. If sulphuric acid reacts with potassium hydroxide what is the name of the soluble salt produced?

Potassium sulphate.

10. If zinc oxide reacts with nitric acid what is the name of the soluble salt produced?

Zinc nitrate

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C2.6 Acids, bases and salts_3

Key Recall Question Answer1. When ammonia dissolves in water does it produce an acid or alkaline solution?

Alkaline

2. How is ammonia solution useful? It is used to produce ammonium salts which are useful as fertilisers

3. Which ion makes solutions acidic? H+4. Which ion makes solutions alkaline? OH-5. What does the pH scale measure? How acidic or alkaline a solution is (essentially how

many H+ or OH- ions are in the solution)6. What is the range of the pH scale? 0-147. What is a neutral pH? 78. What is the pH of a strong acid? 1 or 29. What is the pH of a strong alkali? 13 or 1410. What is a neutralisation reaction? When and acid and alkali react so the H+ ions react

with the OH- ions to produce water.H+(aq) + OH- (aq) H2O(l)

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C2.7 Electrolysis

Key Recall Question Answer1. Why must an ionic substance be melted or dissolved in water before electrolysis can be carried out?

Because when solid the ions are strongly attracted to each other so cannot move. Dissolving or melting the ionic substance means the ions are free to move within the liquid or solution.

2. In order to carry out electrolysis on lead bromide does it need to be dissolved or melted?

Melted

3. What happens when you pass an electric current through molten lead bromide?

It gets broken down into its elements (lead and bromine)

4. What is the term used for a substance that is broken down by electrolysis?

Electrolyte.

5. What happens to the positive and negative ions during electrolysis?

Positively charged ions move to the negative electrode and negatively charged ions move to the positive electrode.

6. What happens to the positive ions at the negative electrode?

The positive ions gain electrons (reduction)

7. What happens to the negative ions at the positive electrode?

The negative ions lose electrons (oxidation)

8. Does oxidation-reduction reactions always involved oxygen?

No, it is about the loss or gain of electrons. Oxidation Is the Loss of electrons and Reduction Is the Gain. (OILRIG)

9. If there is a mixture of ions in the electrolyte, what will the products formed depend on?

The reactivity of the elements involved. The least reactive will be most likely to gain or lose electrons at the electrodes.

10. How are reactions at electrodes represented? By half equations e.g. 2Cl- Cl2 + 2e- or 2Cl- - 2e- Cl2 (where e- represents an electron)

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C2.7 Electrolysis_2

Key Recall Question Answer1. What is electroplating? Where electrolysis is used to plate objects for a

variety of reasons e.g. copper plating or silver plating (cutlery, etc.)

2. How is electrolysis used to manufacture aluminium?

Using a molten (melted) mixture of aluminium oxide and a substance called cryolite.

3. Why is cryolite required in the electrolysis to produce aluminium?

It lowers the melting point of aluminium oxide.

4. In the electrolysis of aluminium oxide, what is formed at the negative electrode?

Aluminium

5. In the electrolysis of aluminium oxide, what is formed at the positive electrode?

Oxygen

6. Which element are electrodes typically made from?

Carbon

7. If oxygen is formed at an electrode, what usually happens?

The oxygen reacts with the carbon in the electrode to form carbon dioxide and the electrode will need to be regularly replaced.

8. What are the products of the electrolysis of sodium chloride solution?

Hydrogen and chlorine (at electrodes). Sodium hydroxide solution is also produced.

9. How are the products of the electrolysis of sodium chloride solution use in industry?

Sodium hydroxide is important for the production of soap and chlorine for the production of bleach and plastics.

10. Can you write the half equation for the oxidation reaction at the positive electrode in the electrolysis of sodium chloride solution?

2Cl- - 2e- Cl2

11. Can you write the half equation for the reduction reaction at the negative electrode in the electrolysis of sodium chloride solution?

2H+ + 2e- H2

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