1. What is this passage mainly about?
A) the use of salt to preserve food B) the recipes for making salami and kimchi
C) how salt was developed as a food source D) how to use salt to prevent bacteria from growing
2. What is NOT mentioned as a characteristic of salt?
A) It dries moisture. B) It preserves food.
C) It contains bacteria. D) It adds flavor to food.
3. Which is NOT true about kimchi?
A) It is enjoyed daily in Korea. B) Kimchi is an old name of chimchae.
C) Kimchi got its name from its ingredients. D) Kimchi has a common ingredient with salami.
4. What can be inferred from this passage?
A) Drying food can be another way to preserve it.
B) People eat less salt because they have refrigerators.
C) The ability of salt to preserve food was discovered in Italy.
D) People had made kimchi even before salt was discovered.
5. Which can replace the word “last” in line 4?
A) finish B) go bad C) live D) stay fresh
56. HOW WE HEAR SOUND
Sound doesn’t have a physical form, but we still hear it. How does this happen? When you hit something, the
air molecules around it start to shake. These vibrating molecules then shake the other molecules nearby. The
vibration is passed on like a wave. When it reaches your ear, it causes tiny hairs inside to shake, too. The
nerves under the hairs sense this and send a message to your brain. Your brain reads this message as sound. In
order to travel, sound needs a medium. This medium can be a solid, a liquid, or a gas. This is why we can’t
hear sound in outer space, where there is no air. Here is a simple experiment to show that sound needs a
medium.
What You Need
• an empty plastic bottle
• a small bell
• a short, firm, hard stick
• matches
• tape
Find the objects listed above. Attach the small bell to the end of the stick. Then, attach the other end of the
stick to the inside of the bottle cap. Put the cap on the bottle and shake it. Can you hear the bell ring? Now,
remove the bottle cap from the bottle. Light a few matches and drop them into the bottle. Quickly put the cap
back on. Wait for the matches to burn out and the bottle to cool. Shake the bottle again. The bell should sound
softer or not be heard at all. Why?
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