1. Chemistry Notes Energy and Heat Heat Capacity and Specific Heat

2. Thermochemistry is the study of heat changes that occur during chemical reactions.

3. Energy is the capacity to do work or supply heat Chemical Potential Energy is stored energy in the bonds of chemical compounds Heat (q) is the energy that transfers due to a difference in temperature (remember temperature is the measure of how much energy something has)

4. Exothermic reactions occur when heat is transferred from the system to the surroundings during a reaction.

5. Endothermic reactions occur when heat is transferred from the surroundings to the system during a reaction.Endothermic reactions occur when heat is transferred from the surroundings to the system during a reaction.

6. Measuring Heat There are two units of heat (q) measurement. calorie - the amount of heat it takes to raise one gram of water by one degree celsius (note: this is different from a food Calorie, which is actually 1 kilocalorie) Joules: 4.184 Joules = 1 calorie

7. Heat capacity is how much heat it takes to raise the temperature of an object by 1 o C. The two variables affect heat capacity are: –Amount of substance –Type of substance

8. Scientists do not generally like to compare heat capacities, because there are two different variables, SO they compared 1g of substances to come up with the specific heat capacity which is also known as specific heat.

9. The amount of energy required to raise the temperature of 1g of substance by 1 o C is its specific heat.

10. The formula for specific heat is: q=(m)(C p )(  T) Heat = mass x specific heat x change in temp.

11. Specific Heat Formula When solved for C p, you get: C p = q__ (m)(  T)

12. Practice Problem #1 When 435J of heat is added to 3.4g of olive oil, it raises the temperature from 21 o C to 85 o C. What is the specific heat of olive oil?

13. Practice Problem #2 A 1.55g piece of stainless steel absorbs 141J of heat when its temperature is increased by 178 o C. What is the specific heat of the stainless steel?

14. Practice Problem #3 How much heat is lost when a 250.0g sample of mercury’s temperature is lowered by 52 o C? C Hg =0.14 J/g o C