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- Fill in the blanks and rewrite the sentence.
a. The amount of water vapour in air is determined in terms of its …………
b. If objects of equal masses are given equal heat, their final temperature will
be different. This is due to difference in their ………………
c. During transformation of liquid phase to solid phase, the latent heat is ………….
- Fill in the blanks and rewrite the sentence.
Answer:_ a) Absolute Humidity
b) Different specific heat capacity
c) Latent heat of Fusion
2) Observe the following graph.
Considering the change in volume of water as its temperature is raised from 0 oC, discuss the difference in the behaviour of water and other substances. What is this behaviour of water called?
ANswer:_
- Most substances expand on heating and contract on cooling.
- Water exhibits a distinct and peculiar behavior between 0oC to 4oC.
- From the graph, it is clear that water contracts instead of expanding between 0oC to 4oC.
- After 4oC, water exhibits normal behavior and expands on heating.
- Water possesses maximum density and minimum volume at 4oC.
- The behavior of water between 0oC to 4oC is known as the anomalous behavior 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 specific heat capacity of a body is the amount of heat energy required to raise the temperature of the unit mass of that body by 1°C (or 1 K). It can be calculated using the formula s = ΔQ / (ΔT x m), where ΔQ is the amount of heat energy supplied, ΔT is the rise in temperature, and m is the mass of the body.
An experiment can be conducted to prove that different substances have different specific heat capacities. Take three balls of iron, copper, and lead of equal mass and put them in boiling water for some time. Then, take them out of the water and measure their temperature. All of them will be at a temperature of 100°C. Now, put them immediately on a thick slab of wax and note the depth that each of the balls goes into the wax. The ball which absorbs more heat from the water will give more heat to the wax, causing more wax to melt and the ball will go deeper into the wax. It will be observed that the iron ball goes the deepest into the wax, the lead ball goes the least, and the copper ball goes to an intermediate depth. This shows that for the equal rise in temperature, the three balls have absorbed different amounts of heat. This means that the property which determines the amount of heat absorbed by a ball is different for the three balls, and this property is called the specific heat capacity.
4) While deciding the unit for heat, which temperatures interval is chosen? Why?
Answer:_
- The unit for heat, which is a calorie, was decided by choosing the temperature interval of 14.5oC-15.5oC.
- The amount of heat released or absorbed by a body is given by the formula
DeltaQ = msDeltaT. - One calorie is defined as the amount of heat required to raise the temperature of 1 g of water through 1oC.
- For 1 calorie of heat energy, the specific heat capacity of water should be 1 cal g-1 oC-1.
- The specific heat capacity of water has been found experimentally to be 1 cal g-1 oC-1 within the temperature range of 14.5oC-15.5oC.
5) Explain the following temperature versus time graph.
Answer:_
- Line AB in the given graph represents the conversion of ice into water at a constant temperature.
- When ice is heated, it melts at 0oC and converts into water while maintaining a constant temperature of 0oC.
- The constant temperature at which ice converts into water is called the melting point of ice.
- During this transition, ice absorbs heat energy, which weakens the bonds between the atoms or molecules in the ice to transform it into liquid.
- The heat energy absorbed by ice, at a constant temperature, to convert it into liquid is called the latent heat of fusion.
- Once all the ice is transformed into water, the temperature of water starts rising and increases up to 100oC.
- Line BC in the graph represents the rise in temperature of water from 0oC to 100oC.
- Beyond 100oC, even though heat energy is supplied to water, its temperature does not rise.
- The heat energy is absorbed by water at this temperature and is used to break the bonds between molecules of the liquid and convert the liquid into a gaseous state.
- Thus, during the transformation from the liquid phase to the gas phase, heat energy is absorbed by the liquid, but its temperature does not change.
- The constant temperature at which the liquid transforms into a gaseous state is called the boiling point of the liquid.
- The heat energy absorbed at a constant temperature during the transformation of liquid into gas is called the latent heat of vaporization.