글로벌 리더로 키우는 쑥쑥영어도서관

Copper Caper

구리로 된 동전과 철로 된 볼트를 식초에 넣고 어떤 변화가 일어나는지 관찰해본다.

20 dull, dirty coins, 1/4 cup white vinegar, 1 teaspoon salt, A clear, shallow bowl (not metal), 2 clean steel nails, A clean steel bolt, Paper towels

1. Put the salt and vinegar in the bowl. Stir until the salt dissolves.

2. Dip one coin halfway into the liquid. Hold it there for about 10 seconds, then pull it out. What do you see?

   3. Dump all the coins into the liquid. You can watch them change for the first
     few seconds. After that you won't see anything happen.
   4. After 5 minutes, take half of the coins out of the liquid. Put them on a paper
      towel to dry.

5. Take the rest of the coins out of the liquid. Rinse them really well under running water, and put them on a paper towel to dry. Write "rinsed" on the second paper towel.

6. Put a nail and a bolt into the liquid. Lean another nail against the side of the bowl so that only part of it is in the liquid.

7. After 10 minutes, take a look at the nails. Are they a different color than they were before? Is the leaning nail 2 different colors? If not, leave the nails in the bowl and check on them again in an hour or so.

8. What's happening to the bolt? You may see lots and lots of fizzing bubbles coming from the threads. Is the bolt changing color? Leave it in the liquid for a while and see what happens.

9. After about an hour, look at the pennies on the paper towels. What's happened to the ones you rinsed? What's happened to the others? What color is the paper towel under the unrinsed coins?

Why did the coins look dirty before I put them in the vinegar?

Everything around you is made up of tiny particles called atoms. Some things are made up of just one kind of atom. The copper of a penny, for example, is made up of copper atoms. But sometimes atoms of different kinds join to make molecules. Copper atoms can combine with oxygen atoms from the air to make a molecule called copper oxide. The coins looked dull and dirty because they were covered with copper oxide.

Why did the vinegar and salt clean the coins?

Copper oxide dissolves in a mixture of weak acid and table salt-and vinegar is an acid. You could also clean your coins with salt and lemon juice or orange juice, because those juices are acids, too.

Why did the unrinsed coins turn blue-green?

When the vinegar and salt dissolve the copper-oxide layer, they make it easier for the copper atoms to join oxygen from the air and chlorine from the salt to make a blue-green compound called malachite.

Why did bubbles come off the steel bolt?

Each water molecule is made up of two hydrogen atoms and an oxygen atom. In an acid (like vinegar or lemon juice), lots of hydrogen ions (hydrogen atoms that are missing an electron) are floating around. In the chemical reactions at the surface of the bolt, some of these hydrogen ions join and form hydrogen gas. The bubbles that you see coming off the bolt are made of hydrogen gas.

식초는 동전을 깨끗하게 만들지만 철은 녹슬게 만든다는 간단한 원리를 보여주는 실험이다. 우리는 동전을 깨끗이 하기 위해 소금과 레몬쥬스나 오렌지 쥬스를 사용할 수도 있다.