Maharashtra Board
2 Mar 2026Heat Class 10 Science 1 Chapter 5 Questions And Answers Maharashtra Board
1. Fill in the blanks and rewrite the sentence. a. The amount of water vapour in air is determined in terms of its……….. Answer. The amount of water vapour in air is determined in terms of its absolute humidity. b. If objects of equal masses are given equal heat, their final temperature will be different. This is due to difference in their…………. Answer. If objects of equal masses are given equal heat, their final temperature will be different. This is due to difference in their specific heat capacities. c. When a liquid is getting converted into solid, the latent heat is………. Answer. When a liquid is getting converted into solid, the latent heat is released. 2. Observe the following graph. Considering the change in volume of water as its temperature is raised from 0 °C, discuss the difference in the behaviour of water and other substances. What is this behaviour of water called? Answer. If the temperature of water is raised from 0 °C to 10 °C, its volume goes on decreasing in the range 0 °C to 4 °C. It is minimum at 4 °C. The volume of water goes on increasing in the range 4 °C to 10 °C. In general, when a substance is heated, its volume goes on increasing with temperature. Thus, in the range 0 °C to 4 °C, behaviour of water is different from other substances. It is called anomalous behaviour of water. 3. What is meant by specific heat capacity? How will you prove experimentally that different substances have different specific heat capacities? Answer. The amount of heat energy required to raise the temperature of a unit mass of an object by 1 °C is called the specific heat capacity of that object. Try this experiment. Material : A tray with thick layer of wax, solid spheres of iron, lead and copper of equal mass, burner or spirit lamp, large beaker.Procedure :(1) Take three spheres of iron, copper and lead of equal mass (Fig.).(2) Put all the three spheres in boiling water in the beaker for some time. (3) Take the three spheres out of the water. All the spheres will be at temperature 100°C. Put them immediately on the thick slab of wax.(4) Note, the depth that each of the sphere goes into the wax. The sphere which absorbs more heat from the water will give more heat to wax. More wax will thus melt and the sphere will go deeper in the wax. It can be observed that the iron sphere goes deepest into the wax. Lead sphere goes the least and copper sphere goes to intermediate depth. This shows that for equal rise in temperature, the three spheres have absorbed different amounts of heat. This means that the property which determines the amount of heat absorbed by a sphere is different for the three spheres. This property is called the specific heat capacity. 4. While deciding the unit for heat, which temperatures interval is chosen? Why? Answer. While deciding the unit for heat, the temperature interval chosen is 14.5 °C to 15.5 °C. For the reason, see the information. If we heat 1 kg of water by 1° C in a different temperature range than 14.5° C to 15.5° C, the amount of heat required is slightly different. It is, therefore, essential to define a specific temperature range while defining the unit of heat. The calorie and the joule are related by the following relation : 1 cal = 4.18 joules. 5. Explain the following temperature versus time graph. Answer. The graph shows what happens when a mixture of ice and water is heated continuously. The temperature of the mixture remains constant (0 °C) till all the ice melts as shown by the line AB. This temperature is the melting point of ice. On further heating, the temperature rises steadily from 0 ° C to 100 °C as shown by the line BC, At 100 °C water starts converting into steam. This temperature is the boiling point of water. Further heating does not change the temperature and the conversion steam continues as shown by the line CD. 6. Explain the following: a. What is the role of anomalous behaviour of water in preserving aquatic life in regions of cold climate? Answer. In cold regions, during winter, the temperature of the atmosphere falls well below 0 °C. As the temperature decreases, the water at the surfaces of lakes and ponds starts contracting. Hence, its density increases and it sinks to the bottom. This process continues till the temperature of all the water in a lake falls to 4 °C. As the water at the surface cools further, i.e., its temperature falls below 4 °C, it starts expanding instead of contracting. Therefore, its density decreases and it remains at the surface. The temperature of the water at the surface continues to fall to 0 °C. Finally, the water at the surface is converted into ice, but the water below the layer of ice is at 4 °C. Ice is a bad conductor of heat. Hence, the layer of the ice at the surface does not allow transfer of heat from the water to the atmosphere. As the water below the layer of ice remains at 4 °C, fish and other aquatic animals and plants can survive in it. b. How can you relate the formation of water droplets on the outer surface of a bottle taken out of refrigerator with formation of dew? Answer. At a given temperature, there is a limit on how much water vapour the given volume of air can hold. The lower the temperature, the lower is the capacity of air to hold water vapour. The temperature of a bottle kept in a refrigerator is lower than room temperature. Hence, when the bottle is taken out of the refrigerator, the temperature of the air surrounding the bottle is lowered. Therefore, the capacity of the air to hold water vapour becomes less. Hence, the excess water vapour condenses to form
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