Bab 4

CHAPTER 4 : HEAT 1

Diagram 1.1 shows a liquid-in-glass thermometer.

DIAGRAM 1.1 (a) (i) Name the liquid P used in the thermometer. ................................................................................................................. (ii)

[ 1 mark] State the physical change in the liquid when the temperature increases. ................................................................................................................. [ 1 mark]

(b) Diagram 1.2 shows two types of thermometers.

DIAGRAM 1.2 (i)

Which thermometer is more sensitive ? ....................................................................................................................... [ 1 mark]

(ii)

State one reason for your answer in 1 (b) (i). ........................................................................................................................ [ 1 mark]

2.

Diagram 1.1 shows a mercury thermometer.

(a)

DIAGRAM 1.1 What is the accuracy of the thermometer?

(b)

........................................................................................................................ [1 mark] Why the glass bulb is made of thin glass? ........................................................................................................................ [ 1 mark]

(c )

Diagram 1.2 shows when thermometer is put into hot water the mercury in the bulb expands and rises up.

DIAGRAM 1.2 (i)

Why the temperature of hot water is taken when the thread of mercury stop expands? ............................................................................................................

(ii)

[1 mark] Give one suggestion how to increased the sensitivity of the thermometer. ............................................................................................................ [1 mark]

3. Diagram 7.1 shows two cups of coffee of equal mass being cooled by adding a few pieces of ice cubes. Ice

Ice

Cup A

Cup B DIAGRAM 7.1

Initially, each cup contains 0.2 kg of coffee at 75.5 oC. It is observed that both cups of coffee reach a final temperature of 25 oC at the same time. (a) The melting of ice involves the absorption of latent heat of fusion. What is meant by specific latent heat of fusion? .........…………………………………………………………………………………… [1 mark]

(b) (i)

(ii)

Which cup of coffee requires more ice? .....................…………………………………………………………………….. [1 mark] Explain your answer in (b)(i). .....................…………………………………………………………………….. .....................…………………………………………………………………….. .....................…………………………………………………………………….. [2 marks]

(c) Calculate the heat released when the coffee is cooled down to 25 oC. [Specific heat capacity of coffee = 4500 J kg–1 oC–1]

[2 marks] (d) (i)

Calculate the mass of ice needed to cool the coffee in cup A to 25 oC. [Specific heat capacity of water = 4200 J kg–1 oC–1, specific latent heat of fusion of ice = 3.36 x 105 J kg–1]

[3 marks] (ii)

State one assumption which you made in your calculation in (d)(i). .....................…………………………………………………………………….. [1 mark]

4. The Diagram 4 shows air being blown into a beaker containing ether. It is later found that ice is formed at the base of the beaker.

DIAGRAM 4 (a)

Name the process that happens to the ether in the situation above. ……………………………………………………………………….. [1 mark]

(b) What is the definition of latent heat?

(c)

……………………………………………………………………… .. [1 mark] Why does ice form at the base of the beaker? …………………………………………………………………………… [2 marks]

(d)

If the specific latent heat of fusion of ice is 3.3 x105 J kg-1, calculate the quantity of heat released when 150 g of water at 0 oC freezes into ice at the same temperature?

[2 marks] (e) State one application of the above phenomenon in everyday life …………………………………………………………………………… [1 mark]

5. Diagram 3.1 shows a metal block P of mass 300 g at initial temperature 100 oC is immersed into the water at room temperature. Diagram 3.2 shows the graph of temperature against time of block P until it achieve thermal equilibrium.

Temperature / oC

100 P

90

water

80 70 60 DIAGRAM 3.1

(a)

DIAGRAM 3.2

50

40 0 20 What is meant by thermal equilibrium?

time / s 40

60 80

100

120

............................................................................................................................................ [1 mark] (b)

What is the temperature of block P when it is in thermal equilibrium?

(c)

............................................................................................................................................ [1 mark] Explain how block P achieve thermal equilibrium. ............................................................................................................................................

(d)

............................................................................................................................................ [2 marks] Calculate the amount of heat lost by block P when its achived thermal equilibrium.

[2 marks]