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

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.

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

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

  2. 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

  3. 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

  4. 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

  5. Hypothesis: I think that Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

  6. Procedure: • Carefully open the zip lock bag containing CaCl2, so that nothing comes out of the bag. • 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

  7. 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

  8. Observations: (record your observations here) Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

  9. 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

  10. 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

  11. 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

  12. 7. Sketch a drawing or graph of the energy changes in this chemical reaction. Unit 4 (Ch. 9) – Reactions/Chem. Living Systems Bach 11/03/09

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