Topic#33: Introduction to Thermochemistry

1. Topic#33: Introduction to Thermochemistry EQ: What is the difference between heat and temperature?

2. Predictions • What will happen to the water temperature in each beaker on the hot plate?Why? • What are three the types of heat transfer? How are they demonstrated? • Assuming I leave the beakers on the hot plates long enough, what will happen? • What will be the same in the two beakers? • What differences will you observe between the two beakers?

3. Types of Heat transfer • Conduction is the transfer of heat energy between substances that are in direct contact with each other. • Convection occurs when areas of a liquid or gas at different temperatures rise and fall to due to density differences. • Radiation does not rely upon any contact between the heat source and heated material, as is the case with conduction and convection.

4. Recall… • What is the law of conservation of energy? • List the forms of energy you know about. Give an example for each form.

5. Water boiling… • What temperature is the water at? • Are we still adding more heat? • Why isn’t the temperature increasing?

6. Turning off the hot plates… • What comparisons can you make about the water temperature and amount of heat energy in each beaker of water at boiling? • Was the same thing true of the beakers of water at room temperature before I started heating them? • So, what is the difference between heat and temperature? Use the words kinetic energy and water molecules. • How long will the transfer of energy take place between two quantities of matter?

7. Conclusions… • Heat and temperature are not the same. • Heat, symbolized by Q, is the energy transferred as a result of a temperature difference. • Temperature, T, is the measure of the average kinetic energy of particles within a material.  • Heat energy transfers from matter at higher temperature to matter at a lower temperature, mostly by conduction and convection.

8. This photo demonstrates the 3 types of heat transfer. Describe them.