Therearetwokindsofchanges—chemicalchangeandphysicalchan...

问题详情：

There are two kinds of changes—chemical change and physical change.

In a chemical change, there is always a new substance(物质) formed. Breaking up water into hydrogen(*气) and oxygen(氧气) is a chemical change. In each of the chemical change at least one new substance is formed. A change is not a chemical change if it doesn’t form a new substance.

Physical changes are very common, too. There are many examples. You can make a physical change by tearing(撕开)a piece of paper in two, or by cutting a piece of iron with lathe(车床). Here paper is still paper, and the iron is still iron.

Another way of making physical change is dissolving(融化) something in water. When you dissolve salt in water, the salt disappears. You may think that a new substance has been formed. But really there is no new substance. The salt is still salt. You can still taste it. So the dissolving of anything is a physical change.

When water freezes, the change is also a physical one. The water changes from liquid(液体) to solid(固体). But it is still the same substance. That is why the freezing of anything is a physical change.

1．It is not ______ if a new substance is not formed in the change.

A．a physical change                  B．a chemical change

C．change of state(状态)            D．a change

2．The dissolving of salt in water is _________.

A．a physical change                  B．a chemical change

C．hydrogen and oxygen             D．breaking up

3．Which is wrong according to the passage?

A．A new substance is always formed in a physical change.

B．Two kinds of changes are talked about in this passage.

C．If a change forms a new substance, it’s a chemical change.

D．The physical changes include the freezing of anything.

【回答】

1B  2A  3A

知识点：日常生活类

题型：阅读填空