1. Topic: Matter & Energy
Aim: What are different types of energy, and how are changes in energy measured?
Do Now: What type of change (phys or chem) is the melting of ice? How do you know?
HW:

2. Forms of Energy Chemical Electrical Thermal Mechanical Nuclear
Electromagnetic

3. Law of Conservation of Matter/Energy
In any change, matter/energy is neither created nor destroyed; it changes form.
A balanced equation shows this law.

4. 2 Types of Energy Changes
Exothermic
Energy released (EXits)
Gas  Liquid (Condensation)
Liquid  Solid (Freezing/Fusion)
Gas  Solid (Deposition)
Endothermic
Energy absorbed (ENters)
Solid  Liquid (Melting)
Liquid  Gas (Evaporation/Boiling)
Solid  Gas (Sublimation)
If matter changes, then energy also changes in some way.

5. Phase Change Relationships

6. Practice Problem
The phase change represented by the equation I2 (s) ----> I2 (g) is called
sublimation
condensation
melting
boiling

7. Changes in Energy
Temperature  measure of average kinetic energy of particles
…so when K.E. of particles increases, temperature _____.
Amount of energy absorbed or released can be calculated based on the temperature change that occurs

8. Remember – we only use C & K

9. Practice Problem
As ice cools from 273 K to 263 K, the average kinetic energy of its molecules will
decrease
increase
remain the same

10. Energy Flow
Heat flows from an area of HIGHER energy to an area of LOWER energy
If you put an ice pack on your injured ankle, heat flows from your ankle to the ice pack, melting the ice.
If you put ice in your drink, the drink loses heat, which is transferred to the ice. As the temperature of the ice rises from the added heat, it eventually melts.
If you touch a hot stove, the heat from the stove is transferred to YOU. YOU don’t cool down the stove! That’s ridiculous!

12. Practice Problem
Solid X is placed in contact with solid Y. Heat will flow spontaneously from X to Y when
X is 20°C and Y is 20°C
X is 10°C and Y is 5°C
X is -25°C and Y is -10°C
X is 25°C and Y is 30°C
- 2, because X has more energy than Y