How to write a secret message Do you want to write a message that can only be read by a person? It is a secret message for that person only. The other people can’t see the message on the paper. Only that person knows how to make the message appear. Here’s an experiment (实验) on how to write such a message. You’ll need halfa lemon a cup four spoons of water a cotton swab (棉签) white paper a light bulb (电灯泡) What to do
1.Squeeze (挤) some lemon juice into water. Mix the water and juice. 2. Put the cotton swab into the mixture (混合物) and make it wet. Use the wet cotton swab to write some words on the paper. 3. Let the paper dry. Show it to someone and ask if he or she can see the words on the paper. 4. Hold the paper close to a light bulb to heat it. Ask him or her again. Let me explain it! Lemon juice has chemicals that have carbon (碳). The chemicals break down easily when they are heated. And the carbon makes them turn a dark color. |
【小题1】If you want to do this experiment, you need the following things EXCEPT ________.
| A．lemon | B．water | C．paper | D．milk |
a. Use a light bulb to heat the paper.
b. Put a cotton swab into the mixture of lemon juice and water.
c. Mix lemon juice and water.
d. Write some words on a piece of white paper with the wet cotton swab.
e. Dry the paper.
| A．adcbe | B．cbaed | C．cbdea | D．aebcd |
| A．when you hold the paper up | B．after you heat the paper |
| C．after you dry the paper | D．when you shake the paper |
| A．To tell us how we can make good use of fruit juice. |
| B．To explain why water is very important in our daily life. |
| C．To tell us why we need to use water and electricity wisely. |
| D．To show how we can use lemon juice and water to write a secret message. |
| A．A science magazine. | B．A storybook. |
| C．A travel guidebook. | D．A cookbook. |
