Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

Calcium Chloride Lab

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

All chemical reactions involve chemical energy, the energy stored in chemical

bonds.

Remember that during a reaction, chemical bonds in the reactants break as they absorb energy. As new bonds form in the products, energy is released.

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

Energy is released or absorbed in the overall reaction depending on how the chemical energy of the reactants compares with the chemical energy of the products.

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

Problem:

Is the chemical reaction involving calcium chloride and water an exothermic reaction or an endothermic reaction?

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

Hypothesis:

I think that

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

Procedure:

1. Carefully open the zip lock bag containing CaCl2, so that nothing comes out of the bag.

2. Using the eyedropper, squirt 2 or 3 full droppers of water into the bag and immediately seal it closed.

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

3. Be very careful that nothing leaks out of your bag. (Do not turn it upside down, etc.)

4. Observe any changes as a result of adding water to the CaCl2.

5. Throw your sealed bag into the trash.

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

Observations:

(record your observations here)

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

Analyze and Conclude:

1. What is an endothermic reaction?

2. What is an exothermic reaction?

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

3. Is the mixture of CaCl2 and water an endothermic or exothermic reaction?

4. How do you know?

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

5. Is the energy of the products in this reaction higher or lower than the reactants?

6. Is heat being released or is heat being absorbed?

Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

7. Sketch a drawing or graph of the energy changes in this chemical reaction.