Antifreeze is a liquid(液体) that is added to water to keep it from freezing． When water freezes and turns to ice，it expands(膨胀)．The force of water expanding is so great that it will break the hardest metal．Water is used in car engines(发动机) to keep them cool while they run，and if this water is allowed to freeze in winter it can break the iron block of the engine．That is why antifreeze is necessary．
Water freezes at 0℃；the usual kind of antifreeze will not freeze until the temperature is－40℃．A mixture(混合物) of five parts of water and four parts of antifreeze will prevent freezing at－18℃；four parts of water and five parts of antifreeze reduce this to －22℃．
Alcohol is a kind of good antifreeze，but when the air is running it becomes hot and the alcohol boils away，so it must be changed very often．Most people use antifreeze that does not boil away when the engine is running．There are several chemicals that do this．One of the most popular is called ethylene glycol．
小题1:people use ________ to keep car engines cool．
A．antifreeze
B．water
C．alcohol
D．ethylene glycol.小题2:The usual kind of antifreeze freezes at ________．
A．0℃
B．－18℃
C．－22℃
D．－40℃小题3:We use antifreeze in order to ________．
A．keep alcohol in water
B．stop ice from becoming water
C．make the freezing point of water lower
D．raise the freezing point of water小题4:Besides alcohol，________ is another kind of popular antifreeze．
A．water
B．ethylene glycol
C．any chemical
D．any mixture小题5:The text is written to ________．
A．tell us what antifreeze is
B．make people buy antifreeze
C．tell us that cars need antifreeze
D．show us how to protect car engines
