Sorting All Sorts of Trash

In some communities, people must separate their recyclable materials into different categories, such as glass (clear or colored), paper, cardboard, aluminum, plastic, etc. Other communities use single-stream recycling, in which everything is put into one large container; sorting occurs later.

If you watched the recycling center videos, you saw that they use some pretty cool methods for separating trash into different types. Sometimes, it's very simple, with a trained sorter picking items out by hand. Other separation methods use magnets or flotation. In this experiment, you will investigate different items that might be in the trash, and will try to figure out ways to separate them all.

What You'll Need:
Pieces of different plastics about 1 inch (2.5 cm) square (find plastics with different numbered recycling codes to ensure that they're different)
Aluminum foil (1 inch or 2.5 cm pieces)
Aluminum can
Steel can
Newspaper (1 inch or 2.5 cm pieces)
Copier paper (1 inch or 2.5 cm pieces)
Magnet
Knitted wool or acrylic item (like a hat or mitten)
Hair dryer
Large bowl
Water

1. Place the magnet near all the different kinds of trash you've collected. Which kinds are attracted to the magnet? Could you use a magnet to remove these from the recycling stream?
2. Rub the knitted item on your hair to give it a static charge. Are any of the trash items attracted to the charged knitwear?
3. Place all of the pieces of trash on a table and aim the blow dryer at them. Turn the dryer on. Which types of trash get blown about, and which ones stay put.
3. Fill the bowl with water and place all of the pieces of trash in the water, one at a time. Which ones float, and which ones sink?
4. Using what you have found, can you figure out a series of sorting techniques that will let you separate all of your trash into different categories? You can use techniques more than once if that helps. If you can't, which things are hardest to separate?

Do the Moola Hula!

Let's talk about some of the places that magnets are used. Did you know that US paper money is partially printed with magnetic ink? Magnetic printing is very difficult to fake, so it helps to protect against counterfeit moola! You can even make a dollar bill dance using a magnet. Fold the dollar in half and position it so that one half is on a flat surface like a table, and the other half sticks straight up into the air. Use a small, but strong, magnet. You will find that certain spots jump when the magnet is nearby - these are the places where the magnetic ink was used. Try other denominations ($5, $10, etc.), and compare old and new bills. If you have any examples of money from other countries, you might check to see if they're magnetic, too!

How Strong?

Magnets come in different strengths. Here's a quick way to compare them. Open a box of paper clips and dump them on a table. Hold a magnet close to the clips. How many paper clips cling to the magnet? What's your record? Part of this has to do with the actual size of the magnet - a magnet that is two inches in diameter will pick up more clips than a one-inch magnet. However, you may find that magnets of about the same size will grab very different numbers of paper clips!

Un-Make A Magnet!

In the last experiment, you made a screwdriver magnetic. But is that change permanent? What if you wanted a non-magnetic screwdriver again. Is there any way to remove the magnetization? In other words, once you've lined up the atomic magnets, is there any way to make them all disorganized again?

Yes, there are a couple of easy ways to do this, but you need to put some energy into the screwdriver blade. You can whack it with a hammer, which disorders the tiny atomic magnets. But this might damage the screwdriver, so it's not the recommended method. You can also heat the screwdriver blade to demagnetize it. Hold the handle with an oven mitt, and touch the blade of a magnetized screwdriver to the burner of an electric stove for about a minute, or put it in the flame of a gas stove for the same amount of time. The blade will get very hot, so don't touch it until it has cooled for about five minutes. Then you should find that it has become an un-magnet, and doesn't pick up paper clips any more!

Make a Magnet!

We tend to think that some things are magnetic, and that some just aren't. But there are some non-magnetic materials that can be magnetized - they can be turned into magnets, and sometimes very simply. Here's an example:


What you'll need:
Screwdriver
Small magnet (not the flexible kind)
Metal paper clips


Hold the tip of the screwdriver near a small pile of paper clips. Does it pick them up? Probably not, because a normal screwdriver isn't a magnet (if your screwdriver is already magnetic, find another one for this experiment).


Hold the screwdriver tightly by the handle in one hand. With the other hand, rub the magnet along the metal part (blade) of the screwdriver, starting near the handle and moving along the blade to the tip. Keep rubbing for about one minute. Now try picking up some paper clips. What happens?


Wow - the screwdriver is now a magnet! But it's made out of the same metal as at the beginning of the experiment. So, some materials can be turned into magnets! How did this happen? The actual explanation is pretty complicated, but here's a simple way to think of this. You probably know that the ends of a magnet are different - it has both a "north" and a "south" pole. The atoms in the screwdriver blade act like little tiny magnets, with itsy-bitsy north and south poles. If the blade is not magnetized, the magnetic atoms are very disorganized, going every which way at once, pulling in every direction. When you rub the metal with a magnet, you help to line up these atoms so that they all point in the same direction. Now they all work together, and the screwdriver acts like a magnet.


Try magnetizing things made out of other materials, such as plastic, wood, or other kinds of metal. You'll find that only certain kinds of metals can be easily magnetized in this way - these metals are called ferromagnetic. This word comes from the Latin name for iron, "ferrum", because the most common magnetizable metal is iron (and steel). However, a few other metals, such as nickel and cobalt, are also referred to as ferromagnetic, even though they're not iron.

Amazing Magnets

This month, we'll be exploring the world of magnetism. Magnets are very common - you know that the earth behaves as a giant magnet, some of your toys likely use magnets, and you probably have a lot of things stuck onto your refrigerator with even more magnets! In the next few weeks, you'll learn about even more places that magnets are used, and more importantly, you'll learn how and why they work. Obviously, you'll need some magnets to do most of these experiments, so you may want to put a few in a safe place so that you'll know where to find them.

Yummy Iron!

It is important that you get plenty of iron in your food, because it helps make sure that your blood can carry oxygen to your muscles. Sometimes, iron is added to foods, like cereal, that doesn't naturally have a lot. You might be surprised to learn that the iron is actually added as tiny bits of metal! And you might be even more surprised to learn that you can actually see them! Here's how:

What you need:
1 cup (250 mL) iron-fortified cereal, such as Total
Gallon-sized (4 L) plastic zipper bag
Rolling pin
Sheet of white paper
Magnet (not the flexible type)

Put the cereal into the plastic bag and seal it closed. Crush the cereal with your fist to break up the flakes, then put the bag on a flat surface and really pulverize the cereal with the rolling pin. It should be like a fine powder when you're done.

Pour a little bit of the cereal powder onto the sheet of paper and spread it out. Put the magnet under the paper and move it around. Do you see any black bits that move? Those are tiny pieces of iron metal!

You might worry about eating metal, but it's OK. The pieces are too small to harm your throat or stomach. And your stomach contains a strong acid that dissolves the metal pieces so that they can get into your body.