D．he felt sad to leave Italy

　　4．What was the main purpose of the writer's visit to Italy?

　　A．To know about the history of a foreign country.

　　B．To prepare an art project for the spring art show.

　　C．To taste all kinds of Italian foods in different cities.

　　D．To buy some special gifts for his family and friends.

　　B

　　Chemical Change and Physical Change

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

　　In a chemical change, there is always a new substance formed. Breaking up water into hydrogen and oxygen 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 a piece of paper into two, or by cutting a piece of iron with lathe (机床). Here paper is still paper, and the iron is still iron.

　　Another way of making physical change is dissolving 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 to solid, but it is still the same substance. That is why the freezing of anything is a physical change.

　　5．In a physical change ________ is formed.

　　A．a new substance B．nothing new

　　C．a piece of paper D．a piece of iron

　　6．The dissolving of salt in water is ________.

　　A．a physical change

　　B．a chemical change

　　C．hydrogen and oxygen

　　D．breaking up

　　7．The change of the three states of water is ________.

　　A．a chemical change

　　B．different substances

　　C．a physical change

　　D．the same state

8．We can separate a chemical change from a physical one by ________.