题目内容
Do you want to write your password down so that no one can see it, or do you want to send someone a secret message? Knowing how to make an invisible ink message will have you feeling like a secret agent in no time. These are instructions for making invisible ink using baking soda.
Difficulty: Easy
Time required: A few minutes
What you need:
Baking soda, Paper, Water, Light bulb, Paintbrush, Measuring cup, Purple grape juice
Here's how:
There are at least two methods of using baking soda as invisible ink. Mix equal amounts of water and baking soda.
Use a paintbrush to write a message onto white paper, using the baking soda solution (溶液) as "ink".
Allow the ink to dry.
One way to read the message is to hold the paper up to a heat source, such as a light bulb. The baking soda will cause the writing in the paper to turn brown.
The second way to read the message is to paint over the paper with purple grape juice. The message will appear in a different color.
Tips:
If you are using the heating method, avoid burning the paper.
Baking soda and grape juice react in an acid-base (酸碱) reaction, producing a color change in the paper.
Grape juice concentrate (浓缩物) results in a more visible color change than regular grape juice.
56. is not needed for making invisible ink.
A. Baking soda B. Paper C. Water D. Ink
57. What's the function of the paintbrush?
A. To draw a picture. B. To allow the "ink" to appear.
C. To write a message onto the white paper. D. To help the "ink" dry.
58. How can you read the message in invisible ink easily?
A. read it in the daytime B. read it near a heater
C. Put it in hot water D. put it in a fridge
59. Why will the message appear in a different color in the second way to read the massage?
A. Because there is enough grape juice. B. Because baking soda reacts with grape juice.
C. Because of the use of water. D. Because of the special paper.
60. From the process, we can know that making invisible ink is .
A. very hard B. not difficult C. a little difficult D. not easy
DCBBB
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