everything in year 8 exams chemistery

Question 1

State the meaning of fuel and combustion.

Answer 1

Fuel is a substance burned for energy. Combustion is a chemical reaction where a fuel reacts with oxygen, releasing energy.

Question 2

Describe the reactants and products in the combustion of hydrocarbons.

Answer 2

Reactants: hydrocarbon + oxygen. Products: carbon dioxide + water.

Question 3

Name the fuel used in a fuel cell.

Answer 3

Hydrogen.

Question 4

Describe the tests for carbon dioxide and water.

Answer 4

Carbon dioxide turns limewater cloudy. Water turns cobalt chloride paper from blue to pink.

Question 5

Write word equations to model reactions.

Answer 5

Example: methane + oxygen → carbon dioxide + water.

Question 6

State the meaning of oxidation.

Answer 6

Oxidation is a chemical reaction where a substance gains oxygen.

Question 7

Describe the reactions of metals with oxygen.

Answer 7

Metals react with oxygen to form metal oxides.

Question 8

Identify reactants and products of oxidation using word equations.

Answer 8

Example: magnesium + oxygen → magnesium oxide.

Question 9

State what happens to mass in a chemical reaction.

Answer 9

Mass is conserved (no overall change).

Question 10

Explain changes in mass seen in reactions.

Answer 10

Mass can appear to change if gases enter or leave during the reaction.

Question 11

Compare and contrast the oxygen and phlogiston theories.

Answer 11

Oxygen theory states substances react with oxygen

Question 12

Name the three sides of a fire triangle and recognise hazard symbols.

Answer 12

Heat, fuel, oxygen. Hazard symbols warn of dangers like flammability.

Question 13

Describe what is meant by an exothermic change.

Answer 13

A change that releases energy, usually as heat.

Question 14

Explain why different types of fire need to be put out in different ways.

Answer 14

Different materials react differently

Question 15

Evaluate data on burning fuels.

Answer 15

Analyze results to judge the efficiency and pollution levels of fuels.

Question 16

Identify variables that need to be controlled in an experiment.

Answer 16

Variables like temperature, concentration, and time should be kept the same.

Question 17

Plan ways in which to control variables in an experiment.

Answer 17

Use the same equipment and settings, control environmental factors.

Question 18

Recall examples of pollutants formed by burning fossil fuels.

Answer 18

Carbon dioxide, carbon monoxide, sulfur dioxide, nitrogen oxides.

Question 19

Describe the reactions of non-metals with oxygen.

Answer 19

Non-metals form acidic oxides with oxygen.

Question 20

Explain the products of complete and incomplete combustion of fossil fuels.

Answer 20

Complete combustion produces carbon dioxide and water

Question 21

Explain how sulfur dioxide and nitrogen can cause acid rain.

Answer 21

They dissolve in water in the atmosphere forming acidic solutions.

Question 22

Explain how pollution from fossil fuel combustion can be reduced.

Answer 22

Use cleaner fuels, scrubbers, and catalytic converters.

Question 23

Evaluate measures for reducing pollution from fossil fuel combustion.

Answer 23

Judge different methods’ effectiveness and costs.

Question 24

State the meaning of greenhouse effect, global warming and climate change.

Answer 24

Greenhouse effect: gases trap heat. Global warming: Earth’s temperature rises. Climate change: long-term changes in weather patterns.

Question 25

Explain how human activities are affecting global warming.

Answer 25

Burning fossil fuels increases greenhouse gases.

Question 26

Explain how methods of controlling carbon dioxide emissions work.

Answer 26

Methods include using renewable energy, capturing carbon, and planting trees.

Question 27

Write and identify the chemical symbols for elements.

Answer 27

Example: H for hydrogen, O for oxygen.

Question 28

Describe Dalton’s ideas on atoms, molecules, elements and compounds.

Answer 28

All matter is made of atoms

Question 29

Write word equations for simple and complex chemical reactions.

Answer 29

Example: iron + sulfur → iron sulfide.

Question 30

Describe elements using physical properties.

Answer 30

Elements are described by properties like melting point, density, color, and conductivity.

Question 31

Explain the difference between physical and chemical changes and properties.

Answer 31

Chemical changes form new substances, physical changes don't.

Question 32

Use observations to decide whether a chemical reaction has taken place.

Answer 32

Signs include gas produced, color change, temperature change, or precipitate formed.

Question 33

Write and interpret chemical formulae for compounds.

Answer 33

Example: H₂O means 2 hydrogen atoms and 1 oxygen atom.

Question 34

Explain what happens during chemical reactions using atomic theory.

Answer 34

Atoms are rearranged into new substances.

Question 35

Carry out calculations involving the masses of reactants and products.

Answer 35

Use the law of conservation of mass.

Question 36

Use the periodic table to find symbols and elements with similar properties.

Answer 36

Elements in the same group have similar properties.

Question 37

Identify alkali metals, halogens and noble gases in the periodic table and describe their typical properties.

Answer 37

Alkali metals: reactive, soft. Halogens: reactive non-metals. Noble gases: unreactive gases.

Question 38

Describe how Mendeleev arranged the elements in the periodic table and made predictions about elements.

Answer 38

Mendeleev grouped elements by properties and left gaps for undiscovered elements.

Question 39

Describe how the modern periodic table is arranged.

Answer 39

By increasing atomic number.

Question 40

Explain what is meant by an anomalous result (outlier).

Answer 40

A result that does not fit the expected pattern.

Question 41

Identify anomalous results and the range of readings in data.

Answer 41

Spot results that are much higher or lower than others.

Question 42

Suggest scientific reasons for anomalous results (outliers).

Answer 42

Could be human error, equipment error, or random chance.

Question 43

State what happens at the melting/freezing/boiling point of a substance.

Answer 43

Substance changes state at a fixed temperature.

Question 44

Use melting, freezing and boiling points to predict state.

Answer 44

If below melting point: solid. If above boiling point: gas.

Question 45

Identify metals and non-metals by their properties and position in the periodic table.

Answer 45

Metals are left and center

Question 46

Describe and identify trends in physical properties in the periodic table.

Answer 46

Example: Group 1 metals become more reactive down the group.

Question 47

Describe the reactions of metals and non-metals with oxygen and water.

Answer 47

Metals form metal oxides, non-metals form acidic oxides.

Question 48

Compare the properties of metal and non-metal oxides.

Answer 48

Metal oxides are basic, non-metal oxides are acidic.

Question 49

Identify trends in chemical properties within a group.

Answer 49

Reactivity increases down Group 1, decreases down Group 7.

Question 50

Make predictions about chemical properties and reactivity in a group.

Answer 50

Predict based on element position in group.

Question 51

Describe the physical and chemical properties of metals and relate them to their uses.

Answer 51

Metals are strong, malleable, good conductors.

Question 52

Recall some reactions that happen slowly and some that happen quickly.

Answer 52

Rusting: slow. Explosions: fast.

Question 53

Describe what catalysts do and some applications of catalysts.

Answer 53

Catalysts speed up reactions without being used up (e.g., in car exhausts).

Question 54

Write word equations for reactions between metals and non-metals.

Answer 54

Example: magnesium + oxygen → magnesium oxide.

Question 55

Describe what happens when metals react with oxygen.

Answer 55

They form metal oxides.

Question 56

State the meaning of corrosion and rusting.

Answer 56

Corrosion is the gradual destruction of metals

Question 57

Explain how barrier methods (e.g., painting) can be used to stop rusting.

Answer 57

They stop air and water reaching the metal surface.

Question 58

Model reactions using word equations.

Answer 58

Example: iron + oxygen + water → hydrated iron(III) oxide (rust).

Question 59

Show the products or reactants in a reaction as formulae.

Answer 59

Example: Fe + O₂ + H₂O → Fe₂O₃·xH₂O.

Question 60

Describe the test for hydrogen.

Answer 60

A burning splint makes a 'pop' sound in hydrogen gas.

Question 61

Write word equations for the reactions of metals with water.

Answer 61

Example: sodium + water → sodium hydroxide + hydrogen.

Question 62

Use the reactions of metals with water to create an order of reactivity.

Answer 62

More reactive metals react faster or more violently with water.

Question 63

Explain how to improve the accuracy of an investigation.

Answer 63

Use more precise equipment, measure carefully.

Question 64

Identify repeated measurements and explain the importance of repeatable, reproducible and reliable data.

Answer 64

Repeat tests to make sure results are consistent and trustworthy.

Question 65

Describe what happens when metals react with acids.

Answer 65

Metals react with acids to produce salt and hydrogen gas.

Question 66

Write word equations for the reactions of metals with different acids.

Answer 66

Example: magnesium + hydrochloric acid → magnesium chloride + hydrogen.

Question 67

Use the reactions of metals with acids to create an order of reactivity.

Answer 67

More reactive metals react faster with acids.

Question 68

Model simple reactions using symbol equations.

Answer 68

Example: Zn + 2HCl → ZnCl₂ + H₂.

Question 69

Describe what happens at a material’s melting, freezing and boiling point.

Answer 69

It changes state (solid, liquid, gas).

Question 70

Describe what is meant by a pure substance and how melting and boiling points can identify pure substances.

Answer 70

Pure substances have fixed melting and boiling points.

Question 71

State, with examples, the meaning of an alloy and explain why alloys are made.

Answer 71

Alloy = mixture of metals, made for better properties (e.g., stainless steel).

Question 72

Use models to explain why alloys are stronger than the pure metal.

Answer 72

Alloy atoms disrupt regular structure, making it harder for layers to slide.