Physics Practical 19 Class 9, 10: Important Viva Voce Questions with Answers : To find the specific heat by the method of mixture using polystyrene cups (used as container of negligible heat capacity).

 PRACTICAL 19

To find the specific heat by the method of mixture using polystyrene cups (used as container of negligible heat capacity). 

VIVA VOCE

1. What is the principle behind the method of mixtures for determining specific heat?

Ans: The principle is based on the law of conservation of energy, where the heat lost by the hot substance is equal to the heat gained by the cold substance, assuming no heat is lost to the surroundings.

2. Why are polystyrene cups used as containers in this experiment?

Ans: Polystyrene cups are used because they have negligible heat capacity and good thermal insulation properties, minimizing heat exchange with the surroundings.

3.  What is specific heat capacity?

Ans: Specific heat capacity is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.

4. Why is it important to ensure that the heat capacity of the container is negligible?

Ans: Ensuring the heat capacity of the container is negligible helps in accurately determining the specific heat capacity of the substance, as it eliminates any heat absorbed by the container itself.

5. How do you ensure that the temperatures of the substances are accurately measured?

Ans: By using calibrated thermometers and ensuring good thermal contact between the thermometer and the substance.

6. What are the possible sources of error in this experiment?

Ans: Possible sources of error include heat loss to the surroundings, inaccurate temperature measurements, and heat exchange with the container if its heat capacity is not truly negligible.

7. How do you calculate the specific heat capacity from the experiment?

Ans: By using the formula: 

q=mcΔT, where $q$ is the heat transferred, $m$ is the mass, $c$ is the specific heat capacity, and ΔT is the temperature change. Set the heat lost by the hot substance equal to the heat gained by the cold substance and solve for the specific heat capacity.

8. Why is it important to stir the mixture during the experiment?

Ans: Stirring ensures uniform temperature distribution throughout the mixture, providing more accurate temperature readings.

9. What assumptions are made in the method of mixtures experiment?

Ans: Assumptions include no heat loss to the surroundings, perfect thermal insulation by the container, and accurate temperature measurements.

10. How would you improve the accuracy of this experiment?

Ans: Improvements could include better insulation, more precise temperature measurements, using a container with even lower heat capacity, and ensuring no heat loss during the transfer of substances.