Rates of Reaction Worksheet - GCSE - Intermediate

Rates of Reaction worksheet for GCSE (Key Stage 4 / GCSE (Ages 14-16)). Intermediate level science practice, aligned to the UK National Curriculum. Print-ready with answer key included.

Science•Key Stage 4 / GCSE (Ages 14-16)•Rates of Reactionintermediate

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Rates of Reaction: Collisions, Catalysts and Graphs

GCSE Chemistry • Key Stage 4 • Intermediate

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Instructions: Answer all five activities using the information provided. Show your working for calculations and use scientific vocabulary where appropriate. Give units with numerical answers.

Factors Affecting Rate

For each situation, identify the factor that changes the rate. Explain the effect using collision theory: state how the change affects collision frequency or the proportion of successful collisions.

1. Magnesium reacts with hydrochloric acid. The acid concentration is increased while all other conditions stay the same. Explain why the reaction is faster.

2. Calcium carbonate reacts with hydrochloric acid. The calcium carbonate is used as smaller chips instead of large lumps. Explain why the reaction is faster.

3. A reaction mixture is heated from 20 °C to 40 °C. Explain why the rate increases, referring to particle energy and successful collisions.

4. A catalyst is added to a reaction mixture. Explain how it increases the rate without being used up.

Collision Theory: Check Your Understanding

Choose the best answer for each question. Think about particle collisions, activation energy and the conditions needed for a reaction to occur.

1. Which statement describes a successful collision?

2. What is the minimum energy particles need to react called?

3. When temperature increases, what happens to the particles?

4. Why does increasing concentration usually increase rate?

Interpreting Reaction-Rate Data

The table shows the volume of gas collected during a reaction. Use the data to compare the rate at different times. For average rates, divide the change in gas volume by the time interval and include units.

Time (s)	Gas volume (cm³)
0	0
20	32
40	54
60	66
80	72

1. Calculate the average rate during the first 20 seconds.

2. Calculate the average rate between 20 and 40 seconds.

3. Between which consecutive 20-second intervals did the gas volume increase by the smallest amount?

4. What does the final reading suggest about the reaction at 80 seconds?

Calculating and Comparing Rates

Use rate = change in quantity ÷ time. Show the calculation for each answer and give the unit. When comparing experiments, identify the changed factor and use the data to support your conclusion.

1. A reaction produces 48 cm³ of gas in 24 s. Calculate its average rate in cm³/s.

2. A reaction produces 30 cm³ of gas in 15 s. Calculate its average rate in cm³/s.

3. Experiment A produces 36 cm³ of gas in 30 s. Experiment B produces 54 cm³ in 30 s. Calculate the rate in each experiment and state which is faster.

4. A student uses a catalyst and collects 40 cm³ of gas in 20 s. Without the catalyst, the same reaction produces 40 cm³ in 50 s. Calculate both average rates and state how the catalyst affects the rate.

Evaluate an Experimental Method

Read the method and answer each question using evidence from it. Focus on controlling variables, measuring rate fairly and explaining the role of a catalyst.

A student investigates how a catalyst affects the reaction between hydrogen peroxide and a solution that produces oxygen. In one trial, the student adds 2 g of catalyst and records the oxygen volume every 10 seconds. In the second trial, no catalyst is added, but the student uses a different volume of hydrogen peroxide and records the oxygen only after 30 seconds.

1. Identify two variables that should be kept the same for a fair comparison.

2. Explain why measuring the oxygen volume at regular time intervals would help the student compare reaction rates.

3. Describe how a catalyst increases the rate, referring to activation energy.

4. Evaluate whether the student's results would allow a valid conclusion. Give one reason and one improvement.

Answer Key

Activity 1: 1. Higher concentration means more acid particles per unit volume, so collisions with magnesium occur more frequently and there are more successful collisions each second. ; 2. Smaller chips have a greater total surface area exposed to the acid, so collisions occur more frequently at the surface. ; 3. Particles have greater average kinetic energy and move faster; collisions are more frequent, and a greater proportion have energy equal to or greater than the activation energy. ; 4. A catalyst provides an alternative reaction pathway with lower activation energy; it is not used up in the reaction.

Activity 2: 1. Particles collide with enough energy and the correct orientation ; 2. Activation energy ; 3. Their average kinetic energy increases ; 4. There are more particles per unit volume, so collisions occur more often

Activity 3: 1. 32 ÷ 20 = 1.6 cm³/s ; 2. (54 − 32) ÷ 20 = 1.1 cm³/s ; 3. 60–80 s ; 4. The volume has decreased from 72 cm³ at 60 s to 66 cm³ at 80 s, so the readings do not support a conclusion that the reaction has simply stopped; the data may include measurement error or gas loss and should be checked.

Activity 4: 1. 48 ÷ 24 = 2 cm³/s ; 2. 30 ÷ 15 = 2 cm³/s ; 3. A: 36 ÷ 30 = 1.2 cm³/s; B: 54 ÷ 30 = 1.8 cm³/s; Experiment B is faster. ; 4. With catalyst: 40 ÷ 20 = 2 cm³/s. Without catalyst: 40 ÷ 50 = 0.8 cm³/s. The catalyst increases the rate.

Activity 5: 1. Any two: volume or concentration of hydrogen peroxide; temperature; mass/surface area of catalyst; total reaction volume; apparatus and gas-collection method. ; 2. Regular readings show how gas volume changes with time, allowing rates over equal time intervals to be calculated and compared. ; 3. It provides an alternative pathway with lower activation energy, so a greater proportion of collisions are successful. ; 4. The comparison is not valid because the hydrogen peroxide volumes differ and the readings are not taken at comparable times. Use the same volume and concentration, keep other conditions constant, and record oxygen volume at regular intervals in both trials.