Compounds and Elements

Burned substance weighs more
If a substance is burned and all the products of its burning - smoke, ash, soot, gas - are captured and weighed, the products together will weigh a little more than did the original substance because they have combined with oxygen.

Diamonds are of carbon
Coal and diamonds are made of the same chemical element - carbon.

Sand makes wall and glass
A brick wall and a plate glass window are made from the same principal ingredient: sand.