"Oh yes," she cried, "we found out that air is an actual substance, which takes up space and has weight, like all other bodies.""We have talked about solid bodies and liquids," Fred went on, "but air is a thin, light substance, which we cannot even see. It is not like either a solid or a liquid.
"Teacher says there are many substances that are like air and differ from both solids and liquids. He turned on the gas-burner to show us one of them. There was nothing to be seen, but we could hear something rushing out of the pipe, and we soon smelt it, and we saw it catch fire when teacher put a match to it.""Oh, you mean the gas," said Norah.
"Yes, but its proper name is coal-gas, because it is made from coal," said Willie.
"All thin, light bodies like these," said Fred, "arecalled gases. Air is a gas, and the invisible vapor in the air is a gas-water-gas. Gases and liquids are alike in some things, but they differ in others.
"What happens when we turn on the faucet over the sink?""The water runs out," said Norah, "becauseliquids flow."
"Can you tell me then why the gas rushed out when teacher turned the burner on?""Well, I suppose it is because the gas flows alongthe pipes," said Norah.
