1. Areated water bottles are kept under water during summer .Why?
2. The size of the weather ballon becomes larger as it ascends into higher altitude .Why?
3. Tyres of automobiles are inflated to lesser pressure in summer than winter.Why?

Aerated water bottle contain excess dissolved oxygen and other  minerals which might get lost when comes in the presence of light.

As we move to higher altitude, the atmospheric pressure decreases, therefore balloon can easily expand to large volume.

In summer due to hot weather condition, the air inside the tyre expands to large volume due to heat as compared to winter therefore inflated to lesser pressure in summer.