10.3.1 Specific Heat and Calorimetry

1. 10.3.1 Specific Heat and Calorimetry Date, Section, Pages, etc. Mr. Richter

2. Agenda • Check and Review HW • Warm Up • Intro to Specific Heat • Notes: • Specific Heat Capacity • Calorimetry • Practice Problems

3. Objectives: We Will Be Able To… • Define specific heat capacity. • Perform calculations with specific heat capacity. • Understand the process of calorimetry and perform calorimetry calculations.

4. Warm-Up: • When you go to the beach in the summer, the sand is often much hotter than the adjacent water. Why is this? • Discuss at your table, and we will discuss as a class in a few minutes.

5. Specific Heat Capacity

6. Specific Heat Capacity • All substances have different molecular structures due to either: • different elements, or • different arrangements of atoms • As a result, different substances require different amounts of energy to raise their temperatures. • Generally, a substance’s specific heat capacity is the amount of energy required to raise the temperature of an object.

7. Specific Heat Capacity • What factors will determine how much energy is required to raise the temperature of a substance? • the mass (how much) • the difference in temperature • “Specifically”: specific heat capacity is the quantity of energy needed to raise the temperature of 1 kg of a substance by 1 °C (at constant pressure) • Units:

8. Specific Heat Capacity p.372

9. Specific Heat Capacity

10. Specific Heat Capacity: Practice Problem • How much energy is required to raise the temperature of 15.0 kg of water by 20.0 °C? • Q = (4186)(15.0)(20.0) • Q = 1.26 x 106 J

11. Calorimetry How is specific heat determined?

12. Calorimetry • The specific heat capacity of water has been studied extensively and is well known. • Cp,water = 4186 J/kg °C • Scientists can use the principles of calorimetry and the specific heat capacity of water to determine the specific heat capacities of other substances. • Calorimetry is the experimental procedure used to measure the energy transfer from one substance to another as heat.

13. Calorimetry: How it works • Place an object with • a known mass • known temperature • unknown specific heat • Into a container of water with: • a known mass • known temperature • known specific heat • When these reach thermal equilibrium, you will know: • how much energy the water absorbed, which is equal to… • how much energy the object lost • From this you can determine the specific heat capacity of the substance.

14. Calorimetry • Heat absorbed by water = heat released by object.

15. Practice Problem • A 0.050 kg metal bolt is heated to an unknown initial temperature. It is then dropped into a beaker containing 0.15 kg of water with an initial temperature of 21.0°C. The bolt and the water then reach a final temperature of 25.0°C. If the metal has a specific heat capacity of 899J/kg °C, find the initial temperature of the metal. • Hint: find the change in temperature of the metal first (solve for ΔTx, then find the initial temp.

16. Wrap-Up: Did we meet our objectives? • Define specific heat capacity. • Perform calculations with specific heat capacity. • Understand the process of calorimetry and perform calorimetry calculations.

17. Homework • Due Monday: • p374 #4, 7