根据下面短文内容填空，每空限填一词。
The students were having their chemistry class. Miss Li was telling the children what water was like. After that, she asked her students, “What is water?” No one answered for a few minutes. Miss Li asked again, “Why don’t you answer my question? Didn’t I tell you what water is like?”
Just then, a boy put up his hand and said, “Miss Li, you told us that water has no color and no smell. But where to find such kind of water? The water in the river behind my house is always black and it has a bad smell.” Most of the children agreed with him.
“I’m sorry, children,” said the teacher, “Our water is getting dirtier and dirtier. That’s a serious problem.”
Miss Li was telling her students about         in a             class.
Miss Li asked the students the same question        ,        no one answered.
We know that water doesn’t         color        smell.
A boy      Miss Li that the water in the river behind       house was always black.
Miss Li felt         because the water        getting dirtier and dirtier.