Year 9 Chemical Reactions Worksheet - Intermediate

Year 9 Chemical Reactions worksheet for Year 9 (Key Stage 3 / Year 7-9 (Ages 11-14)). Intermediate level science practice, aligned to the UK National Curriculum. Print-ready with answer key included.

Science•Key Stage 3 / Year 7-9 (Ages 11-14)•Chemical Reactionsintermediate

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Year 9 Chemical Reactions: Explain, Predict and Calculate

Ages 13–14 | Key Stage 3 | Intermediate

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Instructions: Work through each activity, showing calculations and using precise chemical names and formulae. Use the reactivity series provided where needed. Check that equations are balanced and include state symbols only when the question asks for them.

Word and Symbol Equations

For each reaction, write a balanced symbol equation using the formulae given. Then write the word equation on the line beneath it. Check that each element has the same number of atoms on both sides. [2 marks each]

1. Magnesium reacts with oxygen to form magnesium oxide. Formulae: Mg, O₂, MgO. Balanced symbol equation: Word equation:

2. Calcium carbonate decomposes when heated to form calcium oxide and carbon dioxide. Formulae: CaCO₃, CaO, CO₂. Balanced symbol equation: Word equation:

3. Iron reacts with sulfur to form iron sulfide. Formulae: Fe, S, FeS. Balanced symbol equation: Word equation:

4. Zinc reacts with hydrochloric acid to form zinc chloride and hydrogen. Formulae: Zn, HCl, ZnCl₂, H₂. Balanced symbol equation: Word equation:

Conservation of Mass

Use conservation of mass: atoms are rearranged in a reaction, not created or destroyed. Calculate the missing mass or explain what happens to the mass. Include units in numerical answers. [2 marks each]

1. In a sealed container, 12 g of carbon reacts completely with 32 g of oxygen. What mass of carbon dioxide forms?

2. A reaction in a sealed flask starts with 10 g of reactants. What is the total mass of products after the reaction?

3. A student heats 25 g of copper carbonate. It forms 16 g of copper oxide and carbon dioxide. What mass of carbon dioxide is released?

4. A reaction produces 18 g of gas in an open flask. The measured mass of the flask and contents falls by 18 g. Explain why the measured mass falls, and state whether mass is conserved overall.

Reaction Types: Identify and Explain

Classify each reaction using the most suitable term: combustion, oxidation or thermal decomposition. Some descriptions may involve more than one idea; give the clearest classification and a brief reason. For the equation, identify the substance that is oxidised. [2 marks each]

1. Methane burns in oxygen to form carbon dioxide and water. Name the reaction type and write its word equation.

2. Copper reacts slowly with oxygen in air to form copper oxide. Name the reaction type and state what has combined with the copper.

3. When heated, copper carbonate forms copper oxide and carbon dioxide. Name the reaction type and write its word equation.

4. In the reaction 2Mg + O₂ → 2MgO, which substance is oxidised? Give a reason based on the reaction.

Energy Changes

Decide whether each process is exothermic or endothermic. For temperature changes, use the direction of energy transfer between the reaction and its surroundings. [2 marks each]

1. A hand warmer releases heat to its surroundings as iron reacts with oxygen. Is the reaction exothermic or endothermic?

2. A beaker becomes colder while ammonium nitrate dissolves in water. Is the process exothermic or endothermic?

3. Explain why the temperature of the surroundings rises during an exothermic reaction.

4. Thermal decomposition of calcium carbonate requires continuous heating. Is this reaction exothermic or endothermic? Explain your choice.

Reactivity Series and Displacement

Use this reactivity series, from most reactive to least reactive: magnesium, zinc, iron, copper, silver. A more reactive metal can displace a less reactive metal from its compound. For each question, predict the outcome and give a balanced symbol equation where a reaction occurs. [2 marks each]

1. Zinc is added to copper sulfate solution. Will a reaction occur? If so, name the products and write a balanced symbol equation.

2. Copper is added to magnesium sulfate solution. Will a reaction occur? Explain using the reactivity series.

3. Iron is added to silver nitrate solution. Will a reaction occur? If so, name the products and write a balanced symbol equation.

4. A student places zinc in iron sulfate solution. Predict whether iron is displaced from the solution and explain why.

Answer Key

Activity 1: 1. 2Mg + O₂ → 2MgO; magnesium + oxygen → magnesium oxide ; 2. CaCO₃ → CaO + CO₂; calcium carbonate → calcium oxide + carbon dioxide ; 3. Fe + S → FeS; iron + sulfur → iron sulfide ; 4. Zn + 2HCl → ZnCl₂ + H₂; zinc + hydrochloric acid → zinc chloride + hydrogen

Activity 2: 1. 44 g ; 2. 10 g ; 3. 9 g ; 4. The carbon dioxide escapes from the open flask, so the measured mass falls by 18 g. Mass is conserved overall when the gas is included.

Activity 3: 1. Combustion; methane + oxygen → carbon dioxide + water ; 2. Oxidation; oxygen combines with copper ; 3. Thermal decomposition; copper carbonate → copper oxide + carbon dioxide ; 4. Magnesium; it combines with oxygen to form magnesium oxide.

Activity 4: 1. Exothermic ; 2. Endothermic ; 3. Energy is transferred from the reaction to the surroundings as heat ; 4. Endothermic; energy must be taken in to bring about decomposition.

Activity 5: 1. Yes; zinc + copper sulfate → zinc sulfate + copper; Zn + CuSO₄ → ZnSO₄ + Cu ; 2. No; copper is less reactive than magnesium, so it cannot displace magnesium ; 3. Yes; iron + silver nitrate → iron(II) nitrate + silver; Fe + 2AgNO₃ → Fe(NO₃)₂ + 2Ag ; 4. Yes; zinc is more reactive than iron, so it displaces iron: Zn + FeSO₄ → ZnSO₄ + Fe