# 2 Marks Question

1. An alcohol thermometer can measure the temperature of ice but cannot measure the boiling point of water. Why?
2. The freezing point of alcohol is less than that of water (-117°C) but its boiling point is higher (78°C) higher than that of water. So, alcohol thermometer can measure the temperature of ice but cannot measure the boiling point of water
3. During the winter animals sit into curl, why?
4. The larger the area exposed to the surroundings higher will be the loss of heat and vice versa. So, if less surface area is maintained the animals will not lose more heat. So, during the winter animals sit into curl.
5. Write any two differences between clinical thermometer and laboratory thermometer.
6. Any two differences between clinical thermometer and laboratory thermometer are shown below in table:
Clinical thermometer Laboratory thermometer
Its scale varies from 35°C to 42°C. Its scale varies from -10°C to 110°C.
It is used to measure the temperature of human beings. It is used to measure the temperature of air, water, chemicals.
7. Nowadays clinical thermometer is replaced by digital thermometer. Why?
8. Nowadays clinical thermometer is replaced by digital thermometer because of the following reason:
1. No liquids are used.
2. It is Easy to use.
3. The temperature will show in numbers.
9. A substance having low specific heat capacity gets heated faster than another one with equal mass and having high specific heat capacity, why?
10. We know,
Q = m.s.dt
dt ∝ 1/s (keeping Q and m constant)

Here, change in temperature is inversely proportional to the specific heat capacity. Hence, a substance having low specific heat capacity gets heated faster than another one with equal mass and having high specific heat capacity.

11. 10 kg of water at 80°C cools faster than 15 kg of water at the same temperature kept in the identical vessels. Why?
12. 15 kg of water contains more number of molecules than 10 kg. Large number of molecules make more heat energy. Thus, the less amount of heat contained in 10 kg of water takes short interval of time to loss in the surrounding (it cools faster).
13. In winter morning as soon as we wake up, the air inside the room is cold but if we go out and return to the same room, we feel warm, why?
14. When we wake up in the morning in winter, our body temperature is higher than the temperature of room so we start losing our heat and we feel cold. But when we go out and return to the room, we feel warmer because the temperature inside the room is higher than outside and our body gains heat.
15. Why is water used to cool down the engine of vehicles?
16. Water absorbs a large amount of heat from the engine as it has very high specific heat capacity (4200 J/kg°C). Due to this, water is used to cool down the engine of vehicles.
17. If equal quantity of vegetable oil and water in two different beakers are heated with equal heat, which will increase faster and why?
18. If equal quantity of vegetable oil and water in two different beakers are heated with equal heat, vegetable oil will increase faster because it has less specific heat capacity than water. That is 2000 J/kg°C.
19. If equal amount of heat energy is given to the two objects with equal mass, there will be differences in temperature, why?
20. If the object of equal masses is given equal heat, their final temperature will be different. This is due to difference in their specific heat capacity. It is always constant for the same material and can never be same for two different substances.
21. What is the reason of saying 'heat as a cause and temperature as its effect'?
22. As we add heat to a substance, we speed up the motion of the molecules in substance, hence, we increase their kinetic energy. So, as we add heat to a substance, the temperature Increases. Hence, heat is a cause and temperature is its effect.
23. Write any two differences between heat and temperature. What is the meaning of 'the specific heat capacity of water is 4200 J/kg°C?
24. Differences between heat and temperature is shown below in table:
Heat Temperature
The sum of kinetic energy that the molecules of an object possesses is called heat. The degree of hotness or coldness of a body is called temperature.
It is the cause of temperature. It is the effect of heat.
Its SI unit is joule. Its SI unit is kelvin.
It is measured by calorimeter. It is measured by thermometer.
It means that 4200 joule of heat energy is required to raise or decrease the temperature of 1 kg by 1°C temperature.
25. The night of desert is very cold and the day is very hot. Give reason.
26. The surface of the desert is made up of sand and specific heat capacity of sand is low (800 J/kg°C). Due to this, sand becomes very hot during day as it gets heat from sun. Similarly, the hot sand loses is heat very soon during night as it stop getting heat from sun.
27. What is the cause for using water to cool the hot engine? If two equal sized beakers one having water and another having paraffin oil are heated equally which beaker gains more temperature? Why?
28. Water absorbs a large amount of heat from the engine as it has very high specific heat capacity (4200 J/kg°C). Due to this, water is used to cool the hot engine.
Beaker containing paraffin will gain more temperature because the specific heat capacity of paraffin is less than that of water, so it gets heated faster and cools down too.
29. During high fever, a wet clean cloth as kept on the forehead to the patient, why?
30. When a person is suffering from fever, a wet cloth is kept in forehead to lower his body temperature. As the wet cloth contains water, it can absorb large amount of heat due to its high specific heat capacity. As a result, the temperature of the patient decreases.
31. Write any two reason for using mercury in a thermometer.
32. Reason for using mercury in a thermometer are listed below:
1. It is silver shining liquid which can be easily seen in capillary tube.
2. It has low specific heat capacity.(140 J/kg°C)
Info: It doesn’t wet the wall of capillary tube, it has a uniform rate of expansion over a wide range of temperature (-39 to 357°C), it has high linear expansivity.
33. The temperature of mercury is more when equal amount of heat is given to one kilogram of water and mercury each, why?
34. The specific capacity of mercury (140 J/kg°C) is less than that of water (4200 J/kg°C). So, mercury get heated quickly but water keep absorbing the heat because of its high specific heat capacity. Hence, the temperature of mercury is more when equal amount of heat is given to one kilogram of water and mercury each.
35. The temperature of mercury is more when equal amount of heat is given to one kilogram of water and mercury each, why?
36. The specific capacity of mercury (140 J/kg°C) is less than that of water (4200 J/kg°C). So, mercury get heated quickly but water keep absorbing the heat because of its high specific heat capacity. Hence, the temperature of mercury is more when equal amount of heat is given to one kilogram of water and mercury each.
37. When hot iron nail is kept in cold water, the temperature of iron is reduced, whereas the temperature of water is increased, why?
38. Heat always flow from hot body to cold body. As iron temperature of iron nail is high than water, heat flow from iron nail to water. That is why the temperature of iron is reduced, whereas the temperature of water is increased when a hot iron nail is kept in cold water.
39. Why do specific heat capacity of objects differ?
40. Since the atomic or molecular arrangement of different substances is different. In supplying heat, different substances absorb unequal amounts of heat. In other words, when some amount of heat is supplied for different substances, the rise in temperature becomes maximum because of their atomic or molecular structure. As a result, different substances have different values of specific heat capacity.