1. Energy: Forms and Changes

2. REVIEW  What is an endothermic reaction?  What is an exothermic reaction?  Classify each as endo or exo: Vaporization Freezing Melting Condensation Deposition

3. Let’s Discuss…. Ice Cream  Post-Lab Questions 1. What state of matter was the milk in when you began? When you were done? 2. In order to change the phase of the milk, what had to be removed? 3. What happened to the heat energy that left the milk? 4. What affect did the salt have on the temperature of the ice?

4. 5. Why is it important to have added the salt to the ice? 6. Why did the outside of the bag get wet? (Assume your bag did not spring a leak). 7. Describe the transfer of energy that occurred in this lab.

5.  What does the salt do? Just like we use salt on icy roads in the winter, salt mixed with ice in this case also causes the ice to melt. When salt comes into contact with ice, the freezing point of the ice is lowered. Water will normally freeze at 32 degrees F. A 10% salt solution freezes at 20 degrees F, and a 20% solution freezes at 2 degrees F. By lowering the temperature at which ice is frozen, we are able to create an environment in which the milk mixture can freeze at a temperature below 32 degrees F into ice cream.

6. Forms of Energy  The five main forms of energy are: Thermal (heat) Chemical Electromagnetic (electricity and light) Nuclear Mechanical

7. Thermal Energy (heat)  The internal motion of atoms is called thermal energy, because moving particles produce heat.  Thermal energy can be produced by friction.  Thermal energy causes changes in temperature and phase of any form of matter.

8. Chemical Energy  Chemical energy is required to bond atoms together.  When bonds are broken, energy is released.  Fuel and food are forms of stored chemical energy.

9. Electromagnetic Energy  Power lines carry electromagnetic energy into your home in the form of electricity.

10. Electromagnetic Energy  Light is a form of electromagnetic energy.  Each color of light represents a different amount of electromagnetic energy.  Electromagnetic energy is also carried by X-rays, radio waves, and microwaves.

11. Nuclear Energy  The nucleus of an atom is the source of nuclear energy.  When the nucleus splits (fission), nuclear energy is released in the form of heat energy and light energy.

12. Mechanical Energy  When work is done to an object, it acquires energy. The energy it acquires is known as mechanical energy.

13. Mechanical Energy  When you kick a football, you give mechanical energy to the football to make it move.

14. Energy Conversion  Energy can be changed from one form to another. Changes in the form of energy are called energy conversions.

15. Energy conversions  All forms of energy can be converted into other forms.  What are examples of energy conversion? The sun’s energy through solar cells can be converted directly into electricity. Green plants convert the sun’s energy (electromagnetic) into starches and sugars (chemical energy).

16. States of Energy  The most common energy conversion is the conversion between potential and kinetic energy.  All forms of energy can be in either of two states: Potential – stored energy Kinetic – energy of motion

17. Kinetic Energy  The energy of motion is called kinetic energy.  The faster an object moves, the more kinetic energy it has.  What are we measuring when we measure the kinetic energy of moving particles?

18. Potential Energy  Potential Energy is stored energy. Stored chemically in fuel, the nucleus of atom, and in foods. Or stored because of the work done on it:  Stretching a rubber band.  Winding a watch.  Pulling back on a bow’s arrow.  Lifting a brick high in the air.

19. The Law of Conservation of Energy  Energy can be neither created nor destroyed by ordinary means. It can only be converted from one form to another.