How does temperature affects the density of a substancegive examples related to routine usage?

Answer 1

-- Let a glass of water stand around for a while and eventually the water at the top of the glass is warmer than the water at the bottom of the glass. The warmer water is less dense than the colder water, so it floats on top. -- While you're painting your living room, when you climb the ladder to get at the ceiling, you'll notice immediately that it's pretty warm up there. Since warm air is less dense than cool air, the warm air floats on top, near the ceiling. -- If you try to boil a pot of water with a blow-torch pointed at the top surface, you'll be there all day and still probably fail. If you want to heat a liquid, you apply the heat to the bottom. As the bottom liquid heats, its density decreases and it rises to the top. At the same time, the cooler, more-dense liquid sinks to the bottom ... where the heat is being applied. The reason we heat liquids from the bottom is that this natural circulation ... caused by changes in density and known as 'convection' ... eventually brings all of the liquid to the place where it can be heated. -- You have to get up pretty early in the morning if you want to get out for a ride in your hot-air balloon. After you get the balloon unfolded and laid out on the ground, you have to spend hours heating the air in it. The hotter you make the air in the balloon, the less dense it is; eventually you reduce the density far enough that the balloon can float on the density of the surrounding cooler atmosphere.