Question

a balloon kept in sun burst after some time, why?

Answer 1

because due to high temperature the car in the ballon expands (stated in the gas laws)
hope it helps you

Answer 2

The kinetic energy of gases increases with the increase in the temperature. When the balloon is kept in the sun, due to Sun's heat, the kinetic energy of gaseous particles inside the balloons also gets increased and the balloon expands.

Hope it helps.