下面挑选一个科学实验的例子，提供一些素材给大家，其实还有很多可以选择，时间关系，先去上课，晚上回来再给大家补充关于生物和植物方面的口语素材。

　　Describe a science lesson that you had in school or university.

　　You should say:

　　* when you attended this lesson

　　* where you attended this lesson

　　* how you learned it

　　and explain what you learned.

　　Boiling Frog 温水煮青蛙

　　how you learned it

　　* The boiling frog story states that a frog can be boiled alive if the water is heated slowly enough — it is said that if a frog is placed in boiling water, it will jump out, but if it is placed in cold water that is slowly heated, it will never jump out.

　　* If you put the frog in cold water and slowly increase the temperature--slowly boil the water, the frog will be cooked without trying to jump out.

　　* They say that if you put a frog into a pot of boiling water, it will leap out right away to escape the danger. But, if you put a frog in a kettle that is filled with water that is cool and pleasant, and then you gradually heat the kettleuntil it starts boiling, the frog will not become aware of the threat until it is too late. The frog's survival instincts are geared towards detecting sudden changes.

　　explain what you learned

　　* The story is often used as a metaphor for the inability of people to react to important changes that occur gradually.

　　* Life happens gradually. Like the frog, we can be fooled, and suddenly it’s too late. We need to be aware of what is happening.

　　* This is a story that is used to illustratehow people might get themselves into terrible trouble. This parable is often used to illustrate how humans have to be careful to watch slowly changing trends in the environment, not just the sudden changes. Its a warning to keep us paying attention not just to obvious threats but to more slowly developing ones.

　　* An example: Let's say that every year, the local well had an inch less of water in it. A person might realize there's a problem if there's suddenly NO water, but a slowly dropping level might not be an obvious crisis until it's too late!

　其他素材：

　　Domino Effect 多米诺效应

　　how you learned it

　　* Setting up a chain of dominoes stood on end, and toppling the first domino. That domino topples the one next to it, and so on. In the experiment, however long the chain the dominoes will still fall.

　　explain what you learned

　　* This is because the energy required to topple each domino is less than the energy transferred by each impact, so the chain is self-sustaining. Energy is stored by setting each domino in the metastable upright position, and that energy is what keeps the chain toppling.

　　* The domino effect is a chain reaction that occurs when a small change causes a similar change nearby, which then will cause another similar change, and so on in linearsequence.

　　Coins Turned Green 硬币氧化变绿

　　Materials you will need:

　　Saucer

　　Vinegar