题目内容
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 igniting (点燃) the paper.
Baking soda and grape juice react with each other 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.
B. Paper
C. Water
D. Ink
B. To write a message onto the white paper.
C. To allow the"ink" to appear.
D. To help the"ink" dry.
B. Because baking soda reacts with grape juice.
C. Because of the use of water.
D. Because of the special paper.
B. not difficult
C. a little difficult
D. not easy
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