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LAB in Concentration, Reaction Rate, Reaction Rate. Last updated October 22, 2021.


Summary

In this lab, students explore how temperature and concentration can affect reaction rate. Using various mixtures of OxiClean solutions, blue food coloring, and water students conduct several tests and draw conclusions based on their results.

Grade Level

High School

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

  • HS-PS1-5: Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.
  • Scientific and Engineering Practices:
    • Analyzing and Interpreting Data
    • Planning and Carrying Out Investigations
    • Constructing Explanations and Designing Solutions
    • Engaging in Argument from Evidence

Objectives

By the end of this lab, students should be able to:

  • Determine how temperature and concentration affect the rate of reaction
  • Explain how temperature and concentration affect the rate of reaction in terms of collision theory
  • Predict the rate at which a chemical reaction will occur from given criteria.

Chemistry Topics

This lab supports students’ understanding of:

  • Kinetics
  • Reaction Rate
  • Collision Theory
  • Chemical Reactions
  • Solutions
  • Concentration

Time

Teacher Preparation: 20 minutes
Lesson: 45-60 minutes

Materials

  • OxiClean Powder Versatile Stain Remover (no dyes or perfumes)
  • Blue food coloring
  • Water
  • Digital balance
  • Spoon or scoopula (for measuring out OxiClean)
  • 250 mL beaker, 4 per group
  • 100 mL graduated cylinder, 2 per group
  • 50 mL graduated cylinder, 2 per group
  • Hot plate (for heating water)
  • Ice cubes
  • Stirring rod
  • Stopwatch or timer

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
  • Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.
  • Sodium Carbonate SDS (found in OxiClean)
  • Sodium Percarbonate SDS (found in OxiClean)

Teacher Notes

  • Time Modifications: If you have a shorter class period, here are some things you can prepare in advance to maximize time:
    • Make the two OxiClean mixtures yourself (Procedure Part 1) and have students just do Procedure Parts 2 and 3 in class. The quantities provided for making OxiClean mixtures in the student directions are enough for each group to complete one trial of part 2 and one trial of part 3. Manufacturer instructions suggest dissolving OxiClean powder in warm or hot water and to not store the solutions for more than 6 hours. 
    • Teachers could have a hot- and cold-water bath ready for students to use in part 2 rather than having students heat the water or cool the water themselves.
    • Depending on the length of the lab period, students may either conduct multiple trials themselves or each group can conduct one trial and then combine data from each lab group to analyze data (this is how the student handout is currently designed).
    • Note that for part 2 and part 3, the slower reaction takes about 10 minutes to run to completion.
  • Background and Resources:
    • OxiClean contains sodium percarbonate (Na2CO3·1.5 H2O2) and sodium carbonate (Na2CO3). When dissolved in water, sodium percarbonate breaks down into sodium carbonate, hydrogen peroxide, and oxygen gas. Hydrogen peroxide can act as a bleaching agent by oxidizing and breaking down sections of chemical structures that can cause color.
    • Sodium percarbonate is generally safer to use and more environmentally friendly than household bleach (sodium hypochlorite, NaOCl).
    • In a ChemEdX blog post by Tom Kuntzleman, you can learn about a variation of this lab that includes a video demonstration and data for an AP-level kinetics experiment.
  • Extensions
    • Explore how well OxiClean works on different colors of food dye.
    • Measure the absorbance of the solutions over time using a spectrophotometer or a smartphone color analyzer app (ex: Color Grab).

For the Student

Lesson

Problem

How do temperature and concentration affect the rate at which a reaction occurs?

Background

OxiClean contains sodium percarbonate (Na2CO3·1.5 H2O2) and sodium carbonate (Na2CO3, also known as washing soda). When dissolved in water, sodium percarbonate breaks down into sodium carbonate, hydrogen peroxide, and oxygen gas. Hydrogen peroxide can act as a bleaching agent by oxidizing and breaking down sections of chemical structures that can cause color. Sodium percarbonate is generally safer to use and more environmentally friendly than household bleach (sodium hypochlorite, NaOCl).

Materials

  • OxiClean Powder Versatile Stain Remover (no dyes or perfumes)
  • Water
  • Digital balance
  • Spoon or scoopula (for measuring out OxiClean)
  • 250 mL beakers
  • 100 mL graduated cylinder
  • 50 mL graduated cylinder
  • Hot plate (for heating water)
  • Blue food coloring
  • Ice cubes
  • Stirring rod
  • Stopwatch or timer

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.
  • Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.

Pre-Lab

  1. What do you think of when you hear the word “rate”?
  2. If a reaction is occurring at a faster rate, will the time it takes for the reaction to occur increase or decrease?
  3. Predict how you think temperature and concentration will affect reaction rate.

Procedure: Part 1 (Creating Mixtures)

  1. You will make two different OxiClean mixtures.
  2. Using a graduated cylinder measure the water necessary for OxiClean Mixture A. Place the water in a beaker. *Note that the water should be warm—if warm water isn’t available from the sink, use a hot plate to carefully heat the water.
  3. Using a spoon or scoopula, measure the mass of OxiClean necessary for Mixture A onto the scale. Add it to the water in the beaker.
  4. Stir well until the OxiClean powder is completely dissolved.
  5. Repeat these steps to make OxiClean Mixture B.
  6. Set the mixtures aside and move on to Part 2 of the Procedure.
OxiClean Mixture A
OxiClean Mixture B
13.6 g OxiClean Powder
200 mL warm/hot water
13.6 g OxiClean Powder
100 mL warm/hot water

Procedure: Part 2 (Determining the Effect of Temperature on Reaction Rate)

  1. You will create two blue food dye solutions.
    1. In beaker 1 combine 100 mL hot water and 1 drop blue food coloring. *Note that the water should be hot—if hot water isn’t available from the sink, use a hot plate to carefully heat the water.
    2. In beaker 2 combine 100 mL cold water and 1 drop blue food coloring. *Note that the water should be cold—if cold water isn’t available from the sink, use ice cubes to cool the water.
  2. Gently stir each solution to ensure the blue dye is evenly mixed. 
  3. Obtain two graduated cylinders.
  4. In each graduated cylinder measure 50 mL of “OxiClean Mixture A”:
  5. Next, you will perform step a and b at the same time:
    1. Pour the 50 mL contents of one graduated cylinder (containing “OxiClean Mixture A”) to the cold water blue dye beaker.
    2. Pour the 50 mL contents of the other graduated cylinder (also containing “OxiClean Mixture A”) to the hot water blue dye beaker.
  6. Start a timer.
  7. Gently stir each solution.
  8. Record qualitative observations and the amount of time it takes for the blue color to completely fade in each sample.

Observations & Data

Cold Water
Hot Water
Time (for blue color to completely disappear)
Observations

Class Data: Part 2 (Determining the Effect of Temperature on Reaction Rate)

Collect data from the other groups in the class, and find the average of the results.

Time for Blue Color to Completely Disappear in Cold Water
Time for Blue Color to Completely Disappear in Hot Water
Group #1
Group #2
Group #3
Group #4
Group #5
Group #6
Average

Results

Use the average to write a statement that quantitatively describes the results of Part 2.

Procedure: Part 3 (Determining the Effect of Concentration on Reaction Rate)

  1. You will create two blue food dye solutions.
    1. In beaker 1 combine 100 mL room temperature water and 1 drop blue food coloring.
    2. In beaker 2 combine 100 mL room temperature water and 1 drop blue food coloring.
  2. Gently stir each solution to ensure the blue dye is evenly mixed. 
  3. Obtain two graduated cylinders.
  4. In each graduated cylinder measure premade OxiClean mixtures:
    1. Graduated Cylinder 1: 50 mL “OxiClean Mixture A”
    2. Graduated Cylinder 2: 50 mL “OxiClean Mixture B”
  5. At the same time, add each of the OxiClean to a beaker and start a timer.
  6. Gently stir each solution.
  7. Record qualitative observations and the time it takes for the blue color to completely fade in each sample.

Observations & Data

Beaker containing Water and OxiClean Mixture A
Beaker containing Water and OxiClean Mixture B
Time (for blue color to completely disappear)
Observations

Class Data: Part 3 (Determining the Effect of Concentration on Reaction Rate)

Collect data from the other groups in the class, and find the average of the results.

Time for Blue Color to Completely Disappear using OxiClean Mix A
Time for Blue Color to Completely Disappear using OxiClean Mix B
Group #1
Group #2
Group #3
Group #4
Group #5
Group #6
Average

Results

Use the average to write a statement that quantitatively describes the results of Part 3.

Summary

  1. Write a one-sentence summary of how changing temperature affects reaction rate.
  2. Write a one-sentence summary of how changing concentration affects reaction rate.

Key Idea: In order for a chemical reaction to occur, effective collisions need to occur between the reacting substances. An effective collision needs to have two things:   
  • 1) Sufficient kinetic energy, and
  • 2) Proper orientation.
In order to increase the rate of a chemical reaction, the number of effective collisions between reacting molecules must be increased.
  1. Explain, in terms of collision theory, how increasing temperature affects the rate of a reaction. Use results from the lab in your response. (recall: temperature measures average kinetic energy)
  2. Explain, in terms of collision theory, how increasing the concentration of a reactant affects the rate of a reaction. Use results from the lab in your response.
  3. Why might it be important to slow down or speed up a chemical reaction? Give one example of each.

Application Questions

Answer the following questions using what you have learned about reaction rates.

  1. Given the balanced equation representing a reaction

2 HCl(aq) + Na2S2O3(aq) → S(s) + H2SO3(aq) + 2 NaCl(aq)

Increasing the concentration of Na2S2O3(aq) increases the rate of reaction because the:

a. Activation energy decreases.
b. Activation energy increases.
c. Frequency of effective collisions decreases.
d. Frequency of effective collisions increases.

  1. Why can an increase in temperature lead to more effective collisions between reactant particles and an increase in the rate of a chemical reaction?
    1. The activation energy of the reaction increases.
    2. The activation energy of the reaction decreases.
    3. The number of molecules with sufficient energy to react increases.
    4. The number of molecules with sufficient energy to react decreases.
  1. Given the balanced equation representing a reaction:

Zn(s) + 2 HCl(aq) → H2(g) + ZnCl2(aq)

Which set of reaction conditions produces H2(g) at the fastest rate?

a. 1.0-g lump of Zn(s) in 50 mL of 0.5 M HCl(aq) at 20 degrees Celsius.
b. 1.0-g lump of Zn(s) in 50 mL of 0.5 M HCl(aq) at 30 degrees Celsius.
c. 1.0 g of powdered Zn(s) in 50 mL of 1.0 M HCl(aq) at 20 degrees Celsius.
d. 1.0 g of powdered Zn(s) in 50 mL of 1.0 M HCl(aq) at 30 degrees Celsius.

  1. At 20°C, a 1.2-gram sample of Mg ribbon reacts rapidly with 10.0 milliliters of 1.0 M HCl(aq). Which change in conditions would have caused the reaction to proceed more slowly?
    1. Increasing the initial temperature to 25°C.
    2. Decreasing the concentration of HCl to 0.1 M.
    3. Using 1.2 g of powdered Mg.
    4. Using 2.4 g of Mg ribbon.