1

Thermodynamics

If there was a thermometer attached to the rubber band, what would you observe?

2

Thermodynamics

If there was a thermometer attached to the rubber band, what would you observe?

The temperature goes up

3

Thermodynamics

If there was a thermometer attached to the rubber band, what would you observe?

The temperature goes up

∆Q α ∆T

∆Q is the heat involved

Part 2, A: THERMODYNAMICS

HEAT

27

Units

The unit on heat should be Joules, but oftenpeople use the calorie, or kilocalorie.

1 kcal = amount of heat required to raise 1 kg of water by 1 degree Celcius.

1 kilocal = 4.2 kilojoules4

5

Thermodynamics

Heat

∆Q α ∆T

6

Thermodynamics

Heat

∆Q α ∆T

7

Thermodynamics

Heat

∆Q α ∆T or ∆Q = (slope) m ∆T

∆Q

m∆T

8

Thermodynamics

Heat

∆Q α ∆T or ∆Q = (slope) m ∆T

NOTE: Equal masses

Iron

Water

m∆T

∆Q

Part 2, A: THERMODYNAMICS

HEAT

29

4.2 kJ = amount of heat required to raise 1 kg of water by 1 degree Celcius.

Therefore, for water the slope is

4.2kJ

kg- Co9

10

Thermodynamics

Heat

∆Q = (slope) m ∆T

The slope of this graph is called the specific heat capacity. For

water, the specific heat capacity is

4.2 kj/kg-oC

11

Thermodynamics

Heat

∆Q = (4.2 kj/kg-oC ) m ∆T

How much heat is required to raise the temperature of 10 kg of water by 20 oC?

12

Thermodynamics

Heat

∆Q = (4.2 kj/kg-oC ) m ∆T

How much heat is required to raise the temperature of 10 kg of water by 20 oC?

Heat = (4.2 kj/kg-oC ) (10 kg) (20 oC)= 840 kj

13

Thermodynamics

Heat

∆Q = (slope) m ∆T

NOTE: Equal masses

Clay, Marble

Water∆Q

m∆T

Part 2, A: THERMODYNAMICS

HEAT

31

Question: Water has a high specific heatcapacity. When heat is added or removedfrom water, will this produce a relativelylarge or small change in temperature forthe water as compared to, for example,clay?

14

15

Thermodynamics

Heat

∆Q = (slope) m ∆T

NOTE: Equal masses

Clay, Marble

Water∆Q

m∆T

16

Thermodynamics

Heat

∆Q = (slope) m ∆T

NOTE: Equal masses

Clay, Marble

Water∆Q

m∆T

17

Thermodynamics

Heat

∆Q = (slope) m ∆T

NOTE: Equal masses

Clay, Marble

Water∆Q

m∆T

18

Thermodynamics

Heat

∆Q = (slope) m ∆T

NOTE: Equal masses

Clay, Marble

Water∆Q

m∆TSmall change Large change

Part 2, A: THERMODYNAMICS 31

19

20

Thermodynamics

Heat

∆Q = (slope) m ∆T

The variation in temperature between day and night on mars can be as much as 150 degree Fahrenheit, while the variation in temperature on the earth is far smaller. Why?

Part 2, A: THERMODYNAMICS 31

21