Name: ______/ Date: ______

Investigating Rates of Reaction

Aim

This resource covers a series of 5 lessons during which time students will investigate 5 factors affecting the rate of a chemical reaction, and three methods of investigating rates of reaction. They will be challenged to observe and identify the causes and effects of these factors, as well as to apply How Science Works skills including graph drawing and interpretation, description and explanation of observations.

Learning Outcomes

Each practical has it’s own learning outcomes, specified below. In addition the following learning outcomes apply:

Define rate of reaction

Define collision theory

List ways of finding the rate of a reaction

Explain why a particular method of finding the rate is suitable for a specified reaction

Administration

Students should work in pairs, and the class should be split into 4 groups. Groups should work on a different practical task, and should rotate through each over 4 hours of lesson time.

This should alleviate pressure on equipment, and should allow all students to participate equally.

Students will need copies of the instruction sheets and graph paper.

Students should be reminded of all safety implications before every session. Some techniques will need to be demonstrated before students attempt them (e.g. use of gas syringes).

Suggested timetable:

Lessons 1-4: practical tasks on rotation (sheets attached). Students should be encouraged to work independently, to identify patterns in reactivity under the different conditions. They should be encouraged to think about why changing conditions causes the differences they observe. Allow students to come to their own conclusions, but facilitate with questioning – encourage them to think critically about their work.

Lesson 5: This lesson should serve as a synoptic session, identifying students ideas about the rates of reaction and introducing collision theory in a more formalised way. Following this, it may be useful for students to return to the explanation part of the practical sheets to include details of collision theory in their explanations of their observations.

Specification Link:

AQA GCSE Chemistry C2.4 Rates of Reacton

Edexcel GCSE C2 Chemical Reactions

OCR GCSE 21st Century Chemistry A C6 Chemical Synthesis

OCR GCSE Gateway Chemistry B C3 Chemical Economics

Safety:

The teacher should ensure students observe the usual lab safety precautions, with consideration for any additional aspects the group in question might require.

Hazcards:

50Hydrogen peroxideHarmful

60Manganese and its compoundsHarmful

47A Hydrochloric acidCorrosive

95C Sodium thiosulfate

19B Calcium an strontium salts (2) Low Hazard

Equipment

Practical station:
A / B / C / D
Effect of catalysts / Effect of temperature / Effect of concentration/pressure / Effect of surface area
  • Hydrogen peroxide
  • Manganese(IV) oxide
  • Finely chopped potato
  • Finely chopped liver
  • Stopwatches (4)
  • Conical flasks (4)
  • Gas syringes with bungs & tubing(4)
  • Clamps & stands
  • Measuring cylinders (25cm3)
/
  • Hydrochloric acid (0.2mol/dm3)
  • Sodium thiosulfate (0.2mol/dm3)
  • Stopwatches (4)
  • Conical Flasks (4)
  • Water baths at 30, 40 & 50°C
  • Ice bath
  • Measuring cylinders (10cm3)
  • Cotton wool
  • Thermometers
Please set up with samples of both solutions in each water/ice bath. /
  • Hydrochloric acid (0.2mol/dm3, 0.5 mol/dm3 & 1mol/dm3)
  • Marble chips
  • Stopwatches (4)
  • Conical Flasks (4)
  • Top pan balances (4)
  • Measuring cylinders (25cm3)
  • Cotton wool
/
  • Hydrochloric acid (1mol/dm3)
  • Marble chips (small & large)
  • Stopwatches (4)
  • Conical Flasks (4)
  • Top pan balances (2)
  • Gas syringes with bungs & tubing(4)
  • Clamps & stands
  • Measuring cylinders (25cm3)

Learning Objectives

Effect of catalysts / Effect of temperature / Effect of concentration/pressure / Effect of surface area
| / Define catalyst / ||| / Describe how increasing the temperature affects the rate of reactions / | / State what effect increasing the pressure of reacting gases has on the rate of reaction / ||| / Describe how surface area affects the rate of reaction
||| / Describe how a catalyst affects the rate of a reaction /  / Apply collision theory to explain in detail how and why temperature changes the rate of reaction / ||| / Describe the effect of increasing concentration on the rate of reaction /  / Apply collision theory to explain in detail how surface area affects the rate of reaction
 / Explain in detail why a catalyst would be used in an industrial process /  / Predict how temperature would affect a reaction where particles are in a solid state /  / Apply collision theory to explain in detail the effect of changing concentration or pressure on the rate of reaction /  / Suggest which collisions would not cause a reaction
Experiment A - Measuring the effect of a catalyst on the rate of a reaction
Equipment:
  • Hydrogen peroxide
  • Manganese(IV) oxide
  • Potato
  • Liver (optional)
  • Stopwatch
  • Gas syringe & delivery tubes
  • Conical flask
  • 25cm3 measuring cylinder
  • Clamp & stand
  • Safety spectacles
/ Procedure:
  1. Set up the gas syringe and delivery tubes in a clamp & stand.
Gas syringes are delicate, you must have their use demonstrated.
  1. Add 25cm3 hydrogen peroxide to the conical flask
  2. Add finely chopped potato
  3. Swiftly and carefully connect the flask to the gas syringe
  4. Start the stopwatch
  5. Record the volume of gas released every 10 seconds for 2 minutes.
  6. Repeat with a spatula of manganese(IV) oxide and then chopped liver (optional)

Results:
Time (s) / Volume of gas produced (cm3)
Potato / Liver / MnO2
0
10
20
30
40
50
60
70
80
90
100
110
120
Plot these results on a graph. / Draw and label a diagram of your experiment.
Variables:
Independent variable:
Dependent variable:
Control variables:
/ Explain what caused the observed effects:
Describe your results:
Experiment B - Measuring the effect of temperature on the rate of a reaction
Equipment:
  • Hydrochloric acid (0.2mol/dm3)
  • Sodium thiosulfate (0.2mol/dm3)
  • Stopwatch
  • Conical Flask
  • Water baths at 30, 40 & 50°C
  • Ice bath
  • Measuring cylinder (10cm3)
  • Cotton wool
  • Thermometer
/ Procedure:
  1. Place 10cm3 of room temperature 0.2mol/dm3 hydrochloric acid into a conical flask
  2. Record the temperature of the solutions
  3. Draw an X with a pencil on a piece of plain paper & place underneath the conical flask
  4. Add 10cm3 of sodium thiosulfate
  5. Start the stopwatch
  6. Record how long it takes for the X to be obscured
  7. Repeat the experiment with reactants at different temperatures

Results:
Temp of solutions (°C)
Time taken for solution to go cloudy (s)
Plot these results on a graph. / Draw and label a diagram of your experiment.
Variables:
Independent variable:
Dependent variable:
Control variables:
/ Explain what caused the observed effects:
Describe your results:
Experiment C – Measuring the effect of concentration on the rate of a reaction
Equipment:
  • Hydrochloric acid (0.2mol/dm3, 0.5 mol/dm3 & 1mol/dm3)
  • Marble chips
  • Stopwatch
  • Conical Flask
  • Top pan balance
  • Measuring cylinder (25cm3)
  • Cotton wool
/ Procedure:
  1. Add about 5 marble chips to the conical flask
  2. Add 25cm3 of 0.5 mol/dm3 hydrochloric acid
  3. Place a plug of cotton wool in the neck of the flask
  4. Place the flask on the balance, record the mass and start the stopwatch.
  5. Record the mass every 10 seconds for 2 minutes.
  6. Repeat for 0.2mol/dm3 and 1mol/dm3 concentrations of hydrochloric acid.

Results:
Time (s) / Mass of reaction vessel (g)
0.5mol/dm3 / 0.2mol/dm3 / 1mol/dm3
0
10
20
30
40
50
60
70
80
90
100
110
120
Plot these results on a graph. / Draw and label a diagram of your experiment.
Variables:
Independent variable:
Dependent variable:
Control variables:
/ Explain what caused the observed effects:
Describe your results:
Experiment D – Measuring the effect of surface area on the rate of a reaction
Equipment:
  • Hydrochloric acid (1mol/dm3)
  • Marble chips (small & large)
  • Stopwatch
  • Conical Flask
  • Top pan balance (shared)
  • Gas syringes with bungs & tubing
  • Clamps & stands
  • Measuring cylinders (25cm3)
/ Procedure:
  1. Set up the gas syringe and delivery tubes in a clamp & stand.
Gas syringes are delicate, you must have their use demonstrated.
  1. Add 1g of marble chips to the conical flask
  2. Add 25cm3 hydrochloric acid
  3. Connect the gas syringe and start the stopwatch
  4. Record the volume of gas produced every 10 seconds for 2 minutes.
  5. Repeat for different sized marble chips

Results:
Time (s) / Volume of gas produced (cm3)
Small chips / Large chips / Powdered
0
10
20
30
40
50
60
70
80
90
100
110
120
Plot these results on a graph. / Draw and label a diagram of your experiment.
Variables:
Independent variable:
Dependent variable:
Control variables:
/ Explain what caused the observed effects:
Describe your results: