Question

Milk is poured into a cup of tea and is mixed with a spoon. It is an example of
A) Reversible process
B) Irreversible process
C) Adiabatic process
D) Isothermal process

Answer 1

Hint: We can first see what the given processes in the options mean. After that, it can be analyzed that among these processes, of what process the given statement of milk being poured into tea and mixed is an example of.

Complete answer:
 Before proceeding with the given statement we should know what the given processes (in the options) mean when the two substances are mixed:
If after mixing the two substances, we can separate them and bring them to their original form, then it is a reversible process and if not, then it is an irreversible process.
When there is no loss of heat to the surrounding by the system where the substances are mixed and when this mixing happens with no change in temperature i.e. at a constant temperature, it is called an isothermal process.
Now, the given statement states that milk is poured into a cup of tea and is mixed with a spoon:
We cannot separate the milk and tea after they are mixed thus this process is irreversible and not reversible as their original forms cannot be obtained.
Milk can either be at less or more temperature, then the heat will flow from higher to the lower temperature within the system and not the surroundings but there will always be a change in temperature. Thus, it is an adiabatic process but not isothermal.
Therefore, it can be concluded that the given statement is an example of both irreversible and adiabatic processes

So, the correct answer is “Options B and C”.

Note:
The word ‘iso’ means the same and ‘thermal’ is used to represent heat. So when there is no loss or gain of heat, the temperature remains constant and the process is called isothermal.
Remember that the heat always travels from a substance at a higher temperature to that at a lower temperature.Adiabatic processes can be both reversible and irreversible.