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Unit 1 Living well grammar 课时作业
一、阅读理解
These are instructions for making invisible ink using baking soda.
Difficulty:
Easy
Time
A few minutes
required
What you
Baking soda Paper Water
Light bulb
Paintbrush
need
Measuring cup
Purple grape juice
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.
Here ’ s how:
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.
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
Tips: 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.
1． ______ is not needed for making invisible ink.
A ． Baking soda B ．Paper C．Water D ． Ink
2． What’ s the funct