LAB CHEMICAL REACTIONS

HONORS CHEMISTRY I LAB CHEMICAL REACTIONS

Introduction: When two or more substances are brought together, one of three things can happen;
a. Nothing happens. Each substance retains its own properties and is easily identifiable. Examples include mixing sand and gravel, sulfur powder and iron filings

b. Physical change. Something happens but the original substances can be obtained again. Examples include dissolving, condensation freezing, melting.


c. Chemical change. The original substances change into a new substance that cannot be returned to its original state. Examples include burning, rusting, growing, bleaching.

Chemistry is about change: grass grows; steel rusts; hair is bleached, dyed, “permed “or straightened. Natural gas burns to heat homes; Nylon is produced for jackets, swimsuits and pantyhose; Liquid water is decomposed to hydrogen gas and oxygen gas by an electric current; Grape juice ferments in the production of wine.

These are just a few examples of chemical changes that affect each of us. (Zumdahl “World of Chemistry”).

But how can you tell if a chemical reaction has occurred?

EVIDENCE OF A CHEMICAL REACTION:
Change in temperature……………………
Gas is produced…………………
Light is produced ………………………….
Change is color,,,,,,,,,,,,,,,,,,,,,,,
Precipitate forms……………………….

Also as part of this laboratory experience you will learn the pieces of lab equipment, how to use them and where they are stored. In chemistry lab experiments, each experimenter group must obtain their own equipment as it is need (not at the beginning of the period!!!!) and wash and return it when finished with it.

SAFETY: Wear goggles.

MATERIALS: hydrogen peroxide, yeast, sugar, calcium chloride,
Baking soda, vinegar, salt and water.

Lab Question: How can you tell if a chemical reaction has taken place?

Purpose (objective): 1. conduct tests to check for a chemical reaction.
2. classify the test based on whether a chemical reaction
occurred.
3. use correctly the lab equipment.
4. predict if the reaction is chemical or physical.

In this lab, 6 stations will be set up with a different experiment at each station. You are to move through each station, following the instructions for each and recording your data in your composition book. You may start at any station.

EXPERIMENT #1
HYDROGEN PEROXIDE AND YEAST
Procedure:
1. Pour 40 ml hydrogen peroxide into a 250 ml beaker.
2. Measure and record in data table the initial temperature of the hydrogen peroxide.
3. Add 2.0 g yeast to the beaker and stir gently with the thermometer.
4. Measure and record the temperature immediately after adding the yeast.
5. Observe for three minutes and record any observations.
6. Record the final temperature.
7. Clean your equipment and area.

EXPERIMENT #2
HYDROGEN PEROXIDE AND SUGAR
Procedure:
1. Pour 40 ml of hydrogen peroxide into a 250 ml beaker.
2. Measure and record the initial temperature of the hydrogen peroxide.
3. Add 5 g sugar to the beaker and stir with the thermometer.
4. Measure and record the temperature immediately after adding the sugar.
5. Observe for three minutes and record any observations.
6. Measure and record the final temperature.
7. Clean your equipment and area.

EXPERIMENT #3
WATER AND CALCIUM CHLORIDE
Procedure:
1. Pour 40 ml of water into a 250 ml beaker.
2. Measure and record the initial temperature of the water.
3. Add 5 g of calcium chloride to the beaker and stir with the thermometer.
4. Measure and record the temperature immediately after adding the calcium chloride
5. Observe for three minutes and record any observations.
6. Measure and record the final temperature.
7. Clean your equipment and area.


EXPERIMENT # 4
WATER AND BAKING SODA

Procedure:
1. Pour 40 ml of water into a 250 ml beaker.
2. Measure and record the initial temperature of the water.
3. Add 5 g of baking soda to the beaker and stir with the thermometer.
4. Measure and record the temperature immediately after adding the baking soda.
5. Observe for three minutes and record any observations.
6. Measure and record the final temperature.
7. Clean your equipment and area.


EXPERIMENT #5
VINEGAR AND BAKING SODA

Procedure:
1. Pour 40 ml of vinegar into a 250 ml beaker.
2. Measure and record the initial temperature of the vinegar.
3. Add 5 g of baking soda to the beaker and stir with the thermometer.
4. Measure and record the temperature immediately after adding the baking soda.
5. Observe for three minutes and record any observations.
6. Measure and record the final temperature.
7. Clean your equipment and area.


EXPERIMENT #6
VINEGAR AND SALT

Procedure:
1. Pour 40 ml of vinegar into a 250 ml beaker.
2. Measure and record the initial temperature of the vinegar.
3. Add 5 g of salt to the beaker and stir with the thermometer.
4. Measure and record the temperature immediately after adding the salt.
5. Observe for three minutes and record any observations.
6. Measure and record the final temperature.
7. Clean your equipment and area.



Data table:

Experiment Initial temp Temp after addition Final temp Temp change Observations
1
2
3
4
5
6



Conclusions:
1. What evidence do you have as to whether a chemical reaction took place?
Make a list of the experiments and give evidence for a chemical or physical change for each one.


2. How are the temperature changes you observed in these investigations different than if you put something on the stove or in a refrigerator?

3. If you pour hydrogen peroxide on a cut and a white substance appears, what do you know has taken place? Why?

4. Why was it important to record what you observed at each station?

5. Did some of the reactions have more than one thing happening that would tell you a chemical reaction has taken place? Explain and give specific examples.