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Introduction:
When two soap bubbles combine under isothermal conditions, they form a single soap bubble. In this process, the change in volume and change in area occur. Let's understand the reasons behind these changes.

Explanation:
1. Change in Volume:
- When two soap bubbles combine, they merge their volumes to form a single bubble. The volume is a measure of the amount of space occupied by an object.
- The combined volume of the two bubbles is less than the sum of their individual volumes before the combination.
- This reduction in volume can be explained by the principle of surface tension, which is the force that acts on the surface of a liquid and tends to minimize its area.
- The surface tension of the soap solution causes the soap bubbles to exert an inward force, pulling them towards each other. This force reduces the total volume of the combined bubble.

2. Change in Area:
- The area of a soap bubble is the surface area of the thin soap film that encloses the air inside.
- When two soap bubbles combine, their individual soap films merge to form a single soap film.
- The total area of the soap film after the combination is less than the sum of the individual areas of the soap films before the combination.
- This reduction in area occurs due to the surface tension of the soap solution, which tries to minimize the surface area of the soap film.
- The surface tension acts on the soap film, causing it to contract and reduce its area.

Conclusion:
In the process of two soap bubbles combining under isothermal conditions, the change in volume is a reduction in the total volume of the combined bubble compared to the sum of the individual volumes of the two bubbles. The change in area is a reduction in the total area of the soap film compared to the sum of the individual areas of the soap films. These changes occur due to the surface tension of the soap solution, which tries to minimize the area and volume of the soap bubbles.