# Form 3 Physics Quantity of Heat Video Questions and Answers

Form 3 Physics Quantity of Heat Video Questions and Answers.

In this session, we will work out several physics questions on quantity of heat.

Answers in video format will be given.

Lessons (**20**) * SHARE*

- 1.
(a) State the meaning of the term “heat capacity.” (1 mark) (b) State how pressure affects the melting point of a substance. (3 marks) c) Figure 7 shows a set-up of apparatus that may be used to measure the specific latent heat of vaporization of steam.
(i) Describe how the mass of condensed steam is determined. (3 marks)
(ii) Other than mass and time, state two other measurements that should..

12m 39s - 2.
(a) State two differences between boiling and evaporation. (2 marks) (b) State three ways in which loss of heat by conduction is minimized in a vacuum flask. (3 marks) c) In a certain experiment,50g of dry steam at 1000C was directed into some crushed ice at 00C.(Latent heat of vaporization of water is 2.26 x 106 J/kg, latent heat of fusion for ice is 3.34 x 105J/Kg and
specific heat capacity of

10m 45s - 3.
A student who wanted to take a bath mixed 4 Kg of water at #80^0 C# with 6 Kg of water at #20^0 C#. Determine the final temperature of the water

3m 46s - 4.
a).Explain why it is advisable to use a pressure cooker for cooking at high altitudes. (2 marks) b).Water of mass 3.0Kg initially at #20^0 C# is heated in an electric kettle rated at 3.0 Kw. The water is heated until it boils at #100^0C#.Given that the specific heat capacity of water =4200 J/Kg/K, heat capacity of the kettle = 450 J/K, specific latent heat of vaporization of water =2.3mJ/Kg.

9m 8s - 5.
(a) Figure 10 shows an incomplete set up that can be used in an experiment to determine the speci?c heat capacity of a solid of mass m by electrical method.
(i) Complete the diagram by inserting the missing
components for the experiment (2 marks) (ii) Other than temperature, state three measurements that should be taken. (3 marks)..

6m 40s - 6.
In an experiment to determine the speci?c latent heat of vaporization of water, steam of mass 10 g at #100^oC# is passed into 100 g of Water initially at #20^oC# in a container of negligible heat capacity. The temperature of the Water rises to #70^oC#. (Take the speci?c heat capacity of water as #4.2 x 10^3# J/kg/K and the boiling point of water as #100^oC#)
(i) Determine the speci?c latent heat

6m 39s - 7.
Figure 8 shows a graph of the variation of temperature with time for a pure substance heated at a constant rate.
Assuming that heat transfer to the surroundings is negligible, state the changes observed on the substance in region: (a) BC; (1 mark) (b) DE. (1 marks)

2m 37s - 8.
(a) State the meaning of the term “specific latent heat of fusion”. (1 mark) (b) Figure 8 shows a setup of apparatus used in an experiment to determine the specific latent heat of fusion of ice.
Figure 8
The following readings were noted after the heater was switched on for 5 minutes: - Mass of beaker = 130 g - Mass of beaker + melted ice = 190 g (i) Determine the:

7m 28s - 9.
State why it is necessary to leave an air space in a closed glass bottle of water when it is to be kept in a refrigerator.

2m 0s - 10.
An immersion heater rated 2.5 kW is immersed into a plastic jug containing 2 kg of water and switched on for 4 minutes .Determine; i).The quantity of heat gained by the water, ii).The temperature change for the water; (take specific heat capacity of water as #4.2 times 10^3# J/kg/k).

2m 59s - 11.
Figure 4 shows a graph of temperature against time when pure melting ice at #0^oC# is heated uniformly.
Explain what happens between parts: (i).OA: (ii) AB

3m 35s - 12.
(a) When the temperature of water reaches the boiling point, bubbles rise to the surface. (i) State what is contained in the bubbles. (1 mark) (ii) State the reason why bubbles rise to the surface only at the boiling point. (1 mark) (b) Figure 14 shows a graph of vapor pressure against the temperature of water vapor, in a laboratory where a mercury
barometer indicates a height of 61.8 cm.

16m 14s - 13.
(a) State two factors that affect the boiling point of a liquid ( 2 mks) (b) 100g of a liquid at a temperature of 100 C is poured into a well lagged calorimeter . An electric heater rated 50W is used to heat the liquid. The graph in figure 8 shows the variation of the temperature of the liquid with time. Figure 8 (i) From the graph, determine the boiling point of the liquid...

0m 0s - 14.
a)Define the term heat capacity.(1mark) b).You are provided with the apparatus shown in the figure 9 and a stop watch.
Describe an experiment to determine the the specific latent
heat of steam,L,using the set up.In your answer clearly explain the measurements to be made and how these measurements could be used to determine,L. c).A block of metal of mass 150g at #100^0 C# is dropped

0m 0s - 15.
Water is known to boil at #100^0 C# .A student heated some water and noticed that it boiled at #101^0 C#. State two possible reasons for this observation.

2m 3s - 16.
(a) Define specific latent heat of fusion of a substance (1 mark) (b) Water of mass 200 g at a temperature of #60^0C# is put well lagged copper calorimeter of mass 80g. A piece of ice at #0^0 C# and mass 20 g is placed in the calorimeter and the mixture stirred gently until all the ice melts. The final temperature, T of the mixture is then measured.

11m 20s - 17.
Beaker A contains 200g of water at #0^0 C# while beaker B contains 200g of a mixture of ice and water at #0^0C#. Two identical metal blocks are removed from a hot furnace. One block is dropped into beaker A while the other is dropped into beaker B at the same time. Explain why more water evaporates from beaker A than from beaker B (2 marks) (KCSE 2006 paper 1 question 8)

2m 58s - 18.
Explain why a drop of methylated spirit on the back of the hand feels colder than a drop of water at the same temperature.

1m 50s - 19.
A heating element rated 2.5 kW is used to raise the temperature of 3.0Kg of water through #50^0 C#. Calculate the time required to effect this.(Specific heat capacity of water is 4200J/Kg/K).

2m 23s - 20.
An immersion heater rated 90W is placed in a liquid of mass 2kg. When the heater is switched on for 15 minutes the temperature of the liquid rises from #20^0C# to #30^0 C#. Determine the specific heat capacity of the liquid. (Assume no heat losses).

3m 6s

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