SEE Science (Heat) Notes
Heat
1. There is gap between the tracks of rail, why?
Ans: The metals expand or contract with the changes in temperature. The expansion or contraction depends on the coefficient of thermal expansion of the material. Based on this property of the metal, the gap in between the tracks of rail is provided. If there weren't gaps, the metal would buckle or develop stress fractures as it expanded and contracted.
Ans: The metals expand or contract with the changes in temperature. The expansion or contraction depends on the coefficient of thermal expansion of the material. Based on this property of the metal, the gap in between the tracks of rail is provided. If there weren't gaps, the metal would buckle or develop stress fractures as it expanded and contracted.
Or
The metals expand or contract with the changes in temperature. When the trains move on the track with a speed, heat is produced due to friction as a result the volume of railway track increases, if the gap is not left, it bends and accident may happen. So, to avoid such accident gap between the tracks of rail is made.
The metals expand or contract with the changes in temperature. When the trains move on the track with a speed, heat is produced due to friction as a result the volume of railway track increases, if the gap is not left, it bends and accident may happen. So, to avoid such accident gap between the tracks of rail is made.
2. Name the instrument which is made on the basis of expansion of heat.
Ans: Thermometer is the instrument which is made on the basis of expansion of heat.
3. What does it mean by the specific heat capacity of a substance is 140j/kg0C?
Ans: The specific heat capacity of a substance is 140j/kg0C. It means that 140j of heat energy is required to raise the temperature of 1Kg of a substance by 10C.
4. What is specific heat capacity?
Ans: The amount of heat energy required to raise the temperature of 1Kg of a substance by 10C or 1K is called specific heat capacity.
5. On what factors does the quantity of heat of an object depend?
Ans: The quantity of heat of an object depends on:
a) Mass of an object.
b) Specific heat capacity of an object.
c) Change in temperature of an object.
6. Why does specific heat capacity of objects differ?
Ans: Specific heat capacity of objects differs because objects have different velocity of molecules and different molecular arrangement as well as different heat retaining capacity.
7. Why is the density of water maximum at 40C?
Ans: When water is cooled up to 40C it contracts maximum i.e. its volume is minimum at 40C and when cooled below 40C its volume is increased. Therefore, water has maximum density at 40C.
8. Two objects 'x' and 'y' have equal mass. Object 'x' has more specific heat capacity than object 'y', if both are given equal amount of heat, which object has more temperature and why?
Ans: If both objects 'x' and 'y' are given equal amount of heat, object 'y' would have more temperature because the specific heat capacity of objects 'y' is less than that of objects 'x' i.e. less amount of heat is sufficient to raise the temperature of objects 'y' by 10C.
9. Why is only water used to cool the engine of vehicle?
Ans: Water has the highest specific heat capacity (i.e. 4200J/Kg0C) among all the liquid. Due to its high specific heat capacity, it observes more heat energy from the hot engines without appreciable rise in temperature of it. As a result, the cooling of engines is more effective with water than with any other liquid. Hence, only water is used to cool the hot engine of vehicle.
10. Write the relationship between heat gain or loss by an object with mass.
Ans: The amount of heat gain or loss by an object is directly proportional to the mass of an object.
i.e. Q = msdt
Or, Q α m
11. What is anomalous expansion of water? Write its one advantage.
Ans: Generally, volume of liquids increases on heating but when water at 00C is heated, its volume decreases up to 40C and begins to increase after 40C only. This unusual property shown by the water from 00C to 40C is known as anomalous expansion of water.
Its one advantage is
a) Aquatic animals can stay alive in a frozen pond.
12. The boiling temperature of water cannot be measured with the help of an alcohol thermometer, why?
Ans: The boiling point of water is 1000C while the boiling point of the alcohol is only 780C. Since the boiling point of the water is more than that of the alcohol, therefore the boiling temperature of water cannot be measured with the help of an alcohol thermometer.
13. Write the application of high specific heat capacity of water.
Ans: The applications of high specific heat capacity of water are:
a) Water is used to cool the engine of vehicles as it observes more heat from it and makes cooling effective.
b) Water is used in hot bag because water can obtained more heat energy.
c) Cold water is used to lower down the high fever by keeping wet handkerchief on forehead of the patient.
14. Define heat according to molecular theory? Write C.G.S. unit of the heat.
Ans: The total kinetic energy possessed by all the molecules of a body is called heat.
C.G.S. unit of the heat is calorie.
15. The water pipes in very cold places are burst in winter, why?
Ans: In winter, when water trapped in a pipe cools to 40C, the pipe contains maximum amount of water. When the water cools further from 40C to O0C, it expands considerably. The expansion in volume of water in the pipe gives outward pressure in the pipe due to which the pipe bursts.
16. Two beakers A and B are filled with water at 40C. What happens if beaker A is heated and beaker B is cooled down? Why?
Ans: If the breaker A is heated and beaker B is cooled, water overflows from both beakers. Because water has minimum volume at 40C. Therefore, when the temperature of water rises from 40C, it expands and overflows. Similarly, when the temperature decreases from 40C, the water again expands and overflows.
17. What is specific heat capacity of water?
Ans: The specific heat capacity of water is 4200J/Kg0C.
Ans: The specific heat capacity of water is 4200J/Kg0C.
18. How much joule is there in 1 calorie?
Ans: 1 calorie = 4.2 Joules
Ans: 1 calorie = 4.2 Joules
19. At what temperature the density of water is maximum?
Ans: At 40C temperature the density of water is maximum.
Ans: At 40C temperature the density of water is maximum.
20. Write the differences between heat and temperature?
S.N
|
Heat
|
S.N
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Temperature
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a)
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It is the form of energy which gives the sensation of coldness and hotness.
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a)
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It is the degree of hotness and coldness of a body.
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b)
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Its S.I. unit is Joule (J).
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b)
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Its S.I. unit is kelvin (K).
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c)
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Calorimeter is used to measure it.
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c)
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A thermometer is used to measure it.
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d)
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It measures the total kinetic energy of all the molecule of a substance.
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d)
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It measures the average kinetic energy of the molecule of a substance.
|
21. A beaker is filled with water. No single drop can be added. The temperature of water is 40C. What will happen if it is cooled? Explain with reason.
Ans: If the beaker is cooled, the water in the beaker will overflow because water at 40C has maximum density and lower volume. When a beaker filled with water at 40C is cooled, the density of water decreased and the volume of the water increased.
Ans: If the beaker is cooled, the water in the beaker will overflow because water at 40C has maximum density and lower volume. When a beaker filled with water at 40C is cooled, the density of water decreased and the volume of the water increased.
22. The different in temperature is low near sea. Give reason.
Ans: Sea consist of large amount of water and specific heat capacity of water is very high i.e. 4200J/kg0C. So, water needs large amount of heat energy to increase the temperature. Similarly, water has to lose large amount of heat energy to decrease the temperature. Hence, water gets heated or cooled very slowly which makes the different in temperature low near sea.
Ans: Sea consist of large amount of water and specific heat capacity of water is very high i.e. 4200J/kg0C. So, water needs large amount of heat energy to increase the temperature. Similarly, water has to lose large amount of heat energy to decrease the temperature. Hence, water gets heated or cooled very slowly which makes the different in temperature low near sea.
23. What do you mean by one calorie?
Ans: The amount of heat energy required to raise the temperature of 1g of pure water by 10C or 1K is called 1 calorie.
Ans: The amount of heat energy required to raise the temperature of 1g of pure water by 10C or 1K is called 1 calorie.
24. Write two reasons for using mercury as thermometric liquid.
Ans: Reasons for using mercury as thermometric liquid are:
a) It is a good conductor of heat.
b) It has low specific heat capacity i.e. 460 J/Kg0C.
c) It is opaque and shining.
Ans: Reasons for using mercury as thermometric liquid are:
a) It is a good conductor of heat.
b) It has low specific heat capacity i.e. 460 J/Kg0C.
c) It is opaque and shining.
25. What is heat equation? Write the formula of heat equation?
Ans: The product of mass, specific heat capacity and change in temperature is equal to the heat gained or lost by an object. It is called heat equation.
Heat gained or lost = mass specific heat capacity change in temperature
i.e. Q = m s dt
Ans: The product of mass, specific heat capacity and change in temperature is equal to the heat gained or lost by an object. It is called heat equation.
Heat gained or lost = mass specific heat capacity change in temperature
i.e. Q = m s dt
26. Study the following table
Metal
|
Specific heat capacity
|
X
Y
Z
|
900 J/Kg0C
460 J/Kg0C 380 j/Kg0C |
a) What is mean by the specific heat capacity of metal Y is 460j/kg0C?
Ans: The specific heat capacity of metal Y is 460j/kg0C. It means that 460j of heat energy is required to raise the temperature of 1Kg of metal Y by 10C.
Ans: The specific heat capacity of metal Y is 460j/kg0C. It means that 460j of heat energy is required to raise the temperature of 1Kg of metal Y by 10C.
b) Different metal balls with equal mass are heated to 1000C and put on the wax-slab, which metal ball will penetrate most deep and why?
Ans: Metal ball X will penetrate most deep on the wax-slab when different metal balls with equal mass are heated to 1000C because the specific heat capacity of metal ball X is more than that of others metal balls.
Ans: Metal ball X will penetrate most deep on the wax-slab when different metal balls with equal mass are heated to 1000C because the specific heat capacity of metal ball X is more than that of others metal balls.
c) Which above substance will gain more temperature while heating equal mass of all the three substance supplied with equal amount of heat? Give reason.
Ans: Metal Z will gain more temperature while heating equal mass of all the three substance supplied with equal amount of heat because the specific heat capacity of metal Z is less than that of other metals i.e. less amount of heat is sufficient to raise the temperature of metal Z by 10C.
Ans: Metal Z will gain more temperature while heating equal mass of all the three substance supplied with equal amount of heat because the specific heat capacity of metal Z is less than that of other metals i.e. less amount of heat is sufficient to raise the temperature of metal Z by 10C.
27. Well water is warmer in the morning during winter season, why?
Ans: The specific heat capacity of soil (land surface) is very less as compared to that of water. So, during winter night, the temperature of soil decreases very fast than that of water. As a result, the temperature of water inside the well is higher than the surrounding, this makes well water warmer in the morning during winter season.
Ans: The specific heat capacity of soil (land surface) is very less as compared to that of water. So, during winter night, the temperature of soil decreases very fast than that of water. As a result, the temperature of water inside the well is higher than the surrounding, this makes well water warmer in the morning during winter season.
28. What effect will be seen on the density and the volume of water when it is heated from 00C to 100C.? What is this type of behavior called? How is this type of behavior of water useful for aquatic life?
Ans: When water is heated from 00C to 100C, it contracts up to 40C because the density of water increased and volume of water decreased. Similarly, when it is heated more than 40C it expands because the density of water decreased and volume of water increased.
Such type of behavior of water is called anomalous expansion of water.
In cold countries, fishes and other aquatic creatures survive in the pond due to the anomalous expansion of water even through surface of the pond has frozen to ice.
Ans: When water is heated from 00C to 100C, it contracts up to 40C because the density of water increased and volume of water decreased. Similarly, when it is heated more than 40C it expands because the density of water decreased and volume of water increased.
Such type of behavior of water is called anomalous expansion of water.
In cold countries, fishes and other aquatic creatures survive in the pond due to the anomalous expansion of water even through surface of the pond has frozen to ice.
29. Write the two factor that affect heat energy.
Ans: The two factors that affect heat energy are:
a) Mass of an object.
b) Average kinetic energy of the molecules of an object.
Ans: The two factors that affect heat energy are:
a) Mass of an object.
b) Average kinetic energy of the molecules of an object.
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