The density of air when it is heated decreases
cold air has higher density, by hot air is opposite
Magnesium's mass increases as it becomes magnesium oxide.
The bottle will collapse when the bottle has heated air
ZnCO3, when heated in the absence of air, decomposes to give ZnO and CO2. I think this is the answer.
it becomes low
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Things (almost everything, including air) becomes less dense when it is heated. So warm air rises, and cold air falls.
The copper becomes black!
As the air in the balloon is heated, it expands and becomes less dense, or that is, becomes lighter. This then provides lift to the balloon and the basket. The reason the air in the balloon expands, is because as it is heated, the molecules of air move faster and spread out to fill the entire volume of the balloon.
It expands, rises, and becomes less dense.