To answer this question asked as what type of defect arises when a solid is heated which physical property is affected by it , keep remember basic point to give answer.
Key point to answer this question : when any solid is heated up then due to gaining of heat the density in solid decreases that is why vacancy defects created in solid.
solution : When any solid is heated up it means when some heat it given to any solid , a vacancy is created in the crystal due to this increment in heat in solid . The reason is behind it , On heating, some of the lattice sites are vacant it means the vacancies are created and the density of the solid decreases because the number of ions per unit volume decreases due to heat.
hence due to heating up any solid physical property “density of solid decreases” get affected. due to decrement in density of solid , the ions per unit volume decreases and hence vacancies are created.