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3 and 4 Marks Question

  1. If three liquid A, B and C having equal masses are taken in three same size of beakers and exposed in sunlight. After 10 minutes the increased temperature in each is given in the table:
    Liquid Increased temperature
    A 10°C
    B 8°C
    C 6°C
    1. Which liquid has highest specific heat capacity? Why?
    2. 'C' has highest specific heat capacity because its increase in temperature is low.
    3. If all the three liquids are heated to the same temperature and put in the same beakers separately. Which one cools down faster? Why?
    4. 'A' cool down faster because it has low specific heat capacity.
  3. If a heater with power 2000W runs one hour, it gives 4.2 × 103 KJ heat. What will be the temperature increased in 20 kg of water with temperature 40°C by that heat? (Specific heat capacity of water is 4200J/kg°C)
  4. Here,
    Energy (Q) = 4.2 × 103 KJ = 4.2 × 106 J
    Mass of water (m) = 20 kg
    Initial temperature (t1) = 40°C
    Final temperature (t2) = ?

    Now, we know,
    Q = m.s.dt
    or, 4.2 × 106 = 20 × 4200 × (t2 - 40)
    or, t2 - 40 = 4.2×10620×4200\frac{4.2 × 10^6}{20 × 4200}
    or, t2 - 40 = 0.5 × 102

    ∴ t2 = 90°C.

  5. Study the given table and answer the following questions.
    Substance Specific heat capacity
    X 138J/kg°C
    Y 380J/kg°C
    Z 470J/kg°C
    1. Which one gets cooled faster, if equal mass of these three substances are heated to maintain same temperature and then they are exposed in the air? Why?
    2. 'X' gets cooled faster, if equal mass of these three substances are heated to maintain same temperature and then they are exposed in the air because it has low specific heat capacity than other.
    3. Which one of these three substances needs more heat energy to maintain temperature and why?
    4. 'Z' needs more heat energy to maintain temperature because it has more specific heat capacity than other.
  7. Write the relationship between heat gain or lost by a body with its changed temperature. Why do we wear warm clothes in winter?
  8. The relationship between heat gain or lost by a body with its changed temperature is:

    Q = m.s.dt

    where 'Q' is the amount of heat energy lost or gained, 'm' is the mass of an object, 's' is specific heat capacity and 'it' is a change in temperature.
    In winter the environment around us is colder than our body. As we know heat flow from a hot body to cold body. So, to prevent the flow of heat from our body to the environment around us we do wear warm clothes.
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