Name: ____________________________________ Date: ____________________________ Period: ___________
Chemical Reactions Lab—Part 1
All students
Questions: What are the signs of a chemical reaction? Do all reactions form heat (exothermic)? What is the role of a
catalyst in a reaction?
Research: definitions are on the attached page. Add them to the lab.
Exothermic reaction: _______________________________________________________________________________
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Endothermic reaction:_______________________________________________________________________________
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Catalyst:__________________________________________________________________________________________
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Signs of a chemical change: _________________________________________________________________________
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Today we will be making elephant toothpaste using hydrogen peroxide and a yeast solution, to determine the signs of a
chemical reaction. The reaction is below. Identify and count the elements
in the reaction.
2H2O2 --› 2H2O + O2
Is the reaction balanced? _____________________________________________________________________________
__________________________________________________________________________________________________.
Hypothesis: We will be making the toothpaste using yeast or a yeast solution. Which do you think will create the bigger
reaction, the substance made with yeast or with the yeast solution?
I think ___________________________________________________________________________________ will
make a larger reaction.
NOTE: Based on the materials needed, some groups may be doing the experiment using a yeast solution and some may
be doing the experiment with dry yeast.
STOP—Make a prediction above, before moving on. Will the plain yeast or the yeast solution (yeast & water mixture)
make a larger reaction?
Chemical Reactions Lab—Part 2, alternate lab
Directions: Read over the procedures and the observations for Trial 1 and Trial 2. You will need to do this in
order to complete the back of this sheet.
Trial 1
1. Students made observation on the properties of yeast and peroxide (H2O2).
2. Students placed peroxide and soap in a drink bottle.
3. Yeast was added to the peroxide mixture.
4. Observations were made on the reaction. You will find observations in the data table for trial 1.
Trial 2
1. Students added warm water to the yeast.
2. Students made observation on the properties of the yeast mixture and peroxide (H2O2).
3. Students placed peroxide and soap in a drink bottle.
4. The yeast mixture was added to the peroxide mixture.
5. Observations were made on the reaction. You will find observations in the data table for trial 2.
DATA
Trial 1 observations—
Properties of the yeast
Properties of H2O2
Tan
Grainy
Slight smell-sour
Looks like sand
Solid
Small pieces
cool
Clear
Liquid
Slight smell
Cool—cooler than yeast
Observations from lab
Lots of foam—airy, lots of air bubble, whitish
Foam is very warm, bottom of bottle is hot
Foam covers half the tray
Trial 2 observations—
Properties of the yeast
mixture
Tan
Thick
Sour smell
warm
Properties of H2O2
Clear
Liquid
Slight smell
Cool—cooler than yeast
Observations from lab
Very hot—foam and bottle, hotter than trial 1
Lots of foam—covers bottom of container, more than in trial 1
Foam is creamier, few air bubbles
Conclusions:
DIRECTIONS: Use part 1 and part 2 and the data given to answer the questions below.
1. What type of data was gathered—qualitative or quantitative? Explain your answer. _______________________
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2. What was your hypothesis? ____________________________________________________________________
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3. What was the independent variable in the experiment? _____________________________________________
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4. What was the dependent variable in the experiment? _______________________________________________
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5. What was the experimental group? ______________________________________________________________
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6. What was the control group? ___________________________________________________________________
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Conclusion paragraph:
Restate your hypothesis. Clearly state if the hypothesis was correct or incorrect. Compare the data from Trial 1 and Trial
2 to defend your conclusion that the hypothesis was correct or incorrect.
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Vocabulary
Exothermic reaction- a reaction in which energy (heat or light) is produced as part of the product
Endothermic reaction-a reaction in which energy (heat or light) is used to start the reaction
Catalyst-a substance that is used to start a reaction, but does not change as part of the reaction
Signs of a chemical reaction: temperature change (hot or cold), light formed, new substance formed odor change, color
change