1. Energy and Matter

2. Energy Energy is the capacity to do work or produce heat.
Three forms of energy: Radiant, Kinetic, & Potential
Law of Conservation of Energy: Energy is neither created or destroyed, just changed from form to form.
Measuring energy:
Use a device called a calorimeter to measure heat.
calorie: amount of heat needed to raise 1g of water 1 °C
1 Calorie = 1,000 calories
Joule = SI unit of measure for Energy
1 cal = J

3. Practice with energy conversions
Convert 686,000 Joule to Calories
Cal
686,000 J
1 cal
1 Cal
4.184 J
1,000 cal
~164 Cal
2. Convert 47, 500 calorie to Joule
47,500 cal
4.184 J
198, 740 J
1 cal
~199,000 J

4. Temperature Galileo Galilei: invented first thermometer
There are three temperature scales:
Fahrenheit Scale
Not generally used in science.
Water freezes at 32°F and boils at 212°F.
Celsius Scale
Used in science.
Water freezes at 0°C and boils at 100°C.
Kelvin Scale
SI unit and used in science.
Same temperature increment as Celsius scale.
Absolute zero is the lowest temperature possible.
Absolute zero: 0 K = oC.

5. Temperature Temperature
measure of the average KE of the particles in a sample of matter

6. Temperature
bp H2O
body temp
room temp
fp H2O

7. Temperature Conversions

8. What is the Fahrenheit temperature of an object at 600. K?
Convert Kelvin temperature to Celsius.
Convert the Celsius temperature to Fahrenheit.

9. What is the Fahrenheit temperature of an object at 600.K?
Convert Kelvin temperature to Celsius.
Convert the Celsius temperature to Fahrenheit.

10. Thermal Energy Thermal Energy
the total energy of the particles in a material
KE - movement of particles
PE - forces within or between particles due to position
depends on temperature, mass, and type of substance

11. Thermal Energy A B Which beaker of water has more thermal energy?
B - same temperature, more mass
200 mL
80ºC A
400 mL B

12. Heat Transfer Heat Like work, heat is...
thermal energy that flows from a warmer material to a cooler material
Like work, heat is...
measured in joules (J)
a transfer of energy

13. Three ways Conduction-energy transfer through contact of particles
Water in contact with bottom of pot
Convection-energy transfer through mass movement of particles
Warm water rising to top and cool water sinking to bottom of pot
Radiation-energy transfer through waves
Light/heat from the sun

14. Heat Transfer A B Why does A feel hot and B feel cold?
Heat flows from A to your hand = hot.
Heat flows from your hand to B = cold.
80ºC A
10ºC B

15. Heat Transfer Specific Heat (Cp)
amount of energy required to raise the temp. of 1 kg of material by 1 degree Kelvin
units: J/(kg·K) or J/(kg·°C)

16. Heat Transfer 50 g Al 50 g Cu Al - It has a higher specific heat.
Which sample will take longer to heat to 100°C?
50 g Al
50 g Cu
Al - It has a higher specific heat.
Al will also take longer to cool down.

17. Q = m  T  Cp Heat Transfer Q: heat (J) m: mass (kg)
T: change in temperature (K or °C)
Cp: specific heat (J/kg·K)
– Q = heat loss
+ Q = heat gain
T = Tf - Ti

18. Heat Transfer heat gained = heat lost Calorimeter
Coffee cup Calorimeter
Calorimeter
device used to measure changes in thermal energy
in an insulated system,
heat gained = heat lost

19. Heat Transfer GIVEN: WORK: m = 32 g Q = m·T·Cp Ti = 60°C
A 32-g silver spoon cools from 60°C to 20°C. How much heat is lost by the spoon?
GIVEN:
m = 32 g
Ti = 60°C
Tf = 20°C
Q = ?
Cp = 235 J/kg·K
WORK:
Q = m·T·Cp
m = 32 g = kg
T = 20°C - 60°C = – 40°C
Q = (0.032kg)(-40°C)(235J/kg·K)
Q = – 301 J

20. Heat Transfer GIVEN: WORK: m = 230 g Q = m·T·Cp Ti = 12°C
How much heat is required to warm 230 g of water from 12°C to 90°C?
GIVEN:
m = 230 g
Ti = 12°C
Tf = 90°C
Q = ?
Cp= 4184 J/kg·K
WORK:
Q = m·T·Cp
m = 230 g = 0.23 kg
T = 90°C - 12°C = 78°C
Q = (0.23kg)(78°C)(4184 J/kg·K)
Q = 75,061 J