Book 1 (Chapter 2)

Question 1

Energy (E)

Answer 1

SI Unit: J

Question 2

Power

Answer 2

Rate of energy transfer

Unit: Watt (W)

Power = energy / time

Question 3

How to measure the amount of energy transfer?

Answer 3

Use a joulemeter OR a kilowatt-hour meter to measure the amount of energy transfer.

Question 4

Heat capacity

Answer 4

E absorbed by the object to increase the temperature by 1 degree Celsius = E released by the object to decrease the temperature by 1 degree Celsius

Question 5

Experiment: why do we have to measure the highest temperature instead of the temperature right after switching off the heater?

Answer 5

Heater is still hot after being switched off and the heat is still transferring from the heater to the metal

Question 6

Precaution of the experiment (measuring the specific heat capacity of a metal)

Answer 6

1. Add oil to the holes to improve the thermal contact to reduce heat loss
2. Totally immerse the heater to reduce heat loss
3. Insert plastic plate under the metal/wrap with cotton to reduce heat loss

Question 7

Why can’t we use this experimental set-up to measure the specific heat capacity of wood?

Answer 7

Wood is a poor thermal conductor so that the temperature is not even.

Question 8

Error of the experiment (measuring the c of metal)

Answer 8

Heat loss to the surrounding and heat absorbed by apparatus
The experimental value is larger than the actual value because the energy input by the heater is larger than the energy absorbed by the metal

Question 9

Precaution and error encountered in the experiment measuring the specific heat capacity of water

Answer 9

Precaution:
Add a lid to reduce heat loss to the surroundings by convection
Totally immerse the heater to reduce the heat lost to surroundings

Error:
There is heat loss to the surrounding and some of the heat is absorbed by the apparatus
Experimental value of c is larger than the actual value because the energy input by the heater is larger than the energy output of the water

Question 10

Heating curve and cooling curve

Answer 10

The smaller the temperature difference between the two objects, the slower the rate of heat transfer

Question 11

Mixture and thermal equilibrium

Answer 11

When a hot object is in contact with a cold object, energy (heat) flows from hot object to cold object until they have the same temperature I.e. thermal equilibrium

Question 12

What does high specific heat capacity mean?

Answer 12

A material with high specific heat capacity release / absorbed large amount of heat with little change in temperature,

Question 13

Comparing to the heat capacity of other materials, water has a relatively high specific heat capacity. Why?

Answer 13

Hydrogen bond is strong and the water molecule is small and tight

Question 14

Application of the night specific heat capacity of water

Answer 14

1. Coolant
2. Regulate the temperature of human bodies
   Human is a warm-blooded animal of which the temperature does not change very much with the environment. This is mainly due to the high proportion of water in human body. Even in very cold or very hot environments, temperature of water in the body does not change very much.