题型:阅读理解 题类:常考题 难易度:普通
四川省眉山市第一中学2019-2020学年高一上学期英语开学考试试卷
Mr. Brown was a writer. He wrote many books, and he thought they were quite good. He lived in the city. One morning, he went to a small town near the city to visit a friend. He went there by bus. When he got to the town, he saw a bookshop not far from the bus stop. As it was early, he decided to go in and have a look. There were many books in the shop. He was very happy that all the books in the shop were written by him. "Where are other writer's books?" he asked the man in the shop. The man looked up at him and answered. "Oh, they are all sold out."
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 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. |
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