Monday, January 18, 2010

Eggs-tra Bounce: What Did You Eggs-pect? - Experiement #346

"Can an egg be changed chemically by placing it in different compounds?

You will need:
2 whole raw eggs (in shell)
glass of water
glass of vinegar

What to do: Put one egg in a glass of water and let it stand for a full 24 hours. Place the other egg in the vinegar and let it stand for the same length of time.

What happens: The egg in the water remains the same, while the egg in the vinegar compound now feels and looks like a rubber ball, and no longer has a shell! If you drop it a short distance into the sink, it will actually bounce! Now you know how this experiment got its name.

Why: In the vinegar, a chemical change took place in the eggs. The acetic acid (vinegar) reacted with the calcium carbonate of the eggshell. The change cause the shell to soften and disappear, while the egg in the glass of water did not chemically change. Chemists would say that the shell of the egg in the vinegar becomes "decalcified"."

What happened when CKS tried it?: As soon as we put the eggs in the bowls, the egg in the vinegar had bubbles STRAIGHT away!

The next day, the shell was gone and it looked sort of yellowish and it was squishy and bigger than the egg from the water.

I tried bouncing it in the sink. I bounced it 4 times and then on the 5th time, it popped and the yolk came out. All that was left was a skin and the yolk.

The other egg was hard and small and really white with the shell still on - it didn't seem any different to me.

CKS rating: 5 stars - Better than TV!

Sunday, January 17, 2010

Tip of the Iceberg - Experiment #326

"If all the icebergs in the seas were to melt, would the sea level rise? This very simple experiment will give us the answer, and it's based on a very important compound chemists study - water!

You will need:
warm water
6-8 ice cubes

What to do: Place as many ice cubes as you can into a glass; then fill the glass to the brim with warm water. Wait.

What happens: When the ice cubes melt, the water does not overflow.

Why: The ice cubes simply displace the water in the glass, or the amount of ice that melted was exactly equal to the mass of the ice cubes below the water. Like the ice cubes in the glass, the main part of an iceberg is under water. If all the icebergs were to melt, as did the ice cubes in our experiment, the sea level would remain the same. (It's a different story if ice stored on land [like glaciers] were to melt).

What happened when CKS tried it?: It took almost 3 hours for the ice cubes to melt. There is about half a dollar-size puddle of water in the plate under the glass. The glass is so cold that it's misting up and gets foggy and water starts to form. CMS calls it 'condensation' on the outside of the glass. The water in the plate is coming from the air! Water is condensing from the air and forms drops on the glass. No water spilled over the top of the glass so icebergs melting in the sea would not raise sea level!

CKS rating: 2 stars - I'd rather eat my broccoli.

Banana Split - Experiment #329

"Can you place a banana in a bottle without using your hands? Amaze your friends with this party-trick science experiment. Watch carefully, because the banana is quicker than the eye in this split-second surprise. Moreover, it all has to do with molecules and air. Careful - boiling water involved! Also, it is best to do this in the sink.

You will need:
1/2 banana, peeled
teakettle with boiling water
clean, long, narrow bottle with banana-size mouth
dish towel

What to do: Put the funnel into the bottle neck and carefully fill the bottle almost to the top with boiling water (adult help recommended). Remove the funnel. Wrap a dish towel around the bottle and gently swirl the water around; then pour it out. Quickly, fit the pointed end of the half-banana downwards into the bottle neck so that it makes an airtight plug. (Watch the variables - the size of the banana and bottle neck, the amount of hot water, the time it takes - and be patient! You may have to do this experiment several times to get it right, but you will succeed!)

What happens: The banana is sucked down into the bottom of the bottle.

Why: The heat from the boiling water causes the air inside the bottle to expand, forcing some of it out. When the banana is placed into the mouth of the bottle and the cooling air inside the bottle shrinks again, the air pressure inside is reduced and the greater air pressure outside shoves the banana ahead of it into the bottle. This gives you an idea of what happens when air is removed from a space and nothing takes its place (partial vacuum). Just small differences in air pressure can cause things to move.

What now: You want to recycle the bottle, but the banana is inside it! WHAT CAN YOU DO? Just wait a few days. Let the bacteria in the banana do their chemistry work. Bacteria give off enzymes that break down proteins and starches. The banana will eventually change chemically (ferment) and soften enough to be removed easily." If a monkey tries this, he would want to get it out immediately to eat it!

What happened when CKS tried it?: It worked on the first try! The banana was going so slow, you had to squint a little to see it moving into the bottle. And wait a sec....when it gets in the bottle, it goes 'BOMP'! It sucks in really fast and scares you a little.

CKS rating: 4 stars - Like 3 ice cream cones!

Dry Goods - Experiment #331

"Molecules of air can even stop paper from getting wet in a glass of water.

You will need:
small glass
napkin or paper towel
glass bowl

What to do: Crumple the paper and place it in the bottom of the glass. Make certain it is tight so that the paper will not fall out. Fill the bowl with water. Now, turn the glass upside down over the bowl and lower it until it touches the bottom of the bowl. Lift the glass straight up out of the bowl. Continue to keep it upside down as you dry around and inside the rim of it. Now, take the paper out of the glass.

What happens: The paper inside the glass remains dry.

Why: When the glass is pushed into the water, the molecules of air do not escape but instead are pressed together and act as a shield between the water and the paper. Some water enters the glass, but not enough to wet the paper. The molecules of air take up enough space to block it."

What happened when CKS tried it?: The water spilled out of the bowl onto the table because it was too full. I had to clean it up and empty some water out of the bowl. Then when I tried again, the paper was dry and I didn't spill. Make sure you don't fill it up too high!

CKS rating: 5 stars - Better than TV!

Saturday, January 2, 2010

The Spreading Molecules - Experiment #314

"Do water molecules really move? If so, how fast and how slowly?

You will need:
2 clear glasses
cool and hot tap water
food coloring
medicine dropper

What to do: Fill one glass with cool tap water. Fill the other glass with hot tap water. Now, quickly place one drop of food coloring in each glass. (Make certain that all of the variables are the same. This means the glasses should have the same amount of water in them and that the same number of food coloring drops are added. Controlling variables is important to make the experiment scientifically correct.)

What happens: The food coloring spreads throughout the water in both glasses, but at different rates.

Why: The cold water eventually becomes completely colored because the water molecules are moving throughout the glass. But when the water is warmer (the hot tap water), the heat energy in it causes the water molecules to move much faster. This makes the food coloring spread out more rapidly. You might want to chart, or keep a record of, how much time it takes for the food coloring to spread evenly throughout each glass of water."

What happened when CKS tried it? We used boiling water and cold water from the fridge. The hot water spread first and the cold water spread last. It took the hot water 1 minute and 4 seconds, and the cold was 2 minutes and 33 seconds.

CKS rating: 3 stars - Good but not that good

Color Fun - Experiment #25

"Is green really green?

You will need:
strip of paper towel
green felt-tipped pen or 1 drop of green food coloring
jar or glass with 1 inch of water

What to do: Make a spot of color about 2 inches from one end of the strip of paper towel. Hang the strip in the jar so the spot is above the water and the end of the strip is in the water. Let it stand for 15 to 20 minutes.

What happens: The green spot is gone but above the original spot, the paper has turned blue, and above that the paper is yellow.

Why: Most dyes and inks are combinations of coloring substances which can be taken apart by adding water or alcohol. Water moves up the paper the same way as sap rises in trees. As the water moves up, it dissolves the green spot and gradually moves the color up the strip of paper. But since the colors that make up green - blue and yellow - do not move at the same rate, they separate."

What happened when CKS tried it? I tried ink and food coloring. The food coloring was opposite from the ink because the blue is at the top, the green is in the middle, and only a little yellow at the bottom. And on the ink, there is a lot of yellow on the top and there is a little green in the middle, and some blue on the bottom. Ink worked better. Advice from CKS for when you try this at home: don't forget to label your paper towel strips.

CKS rating: 5 stars - Wow, better than TV!

Invisible Ink - Experiment #28

"You can use a lemon to write a secret message.

You will need:
1/2 lemon
cotton swab (Q-tip)
white paper

What to do: Squeeze the lemon juice into the saucer. Add a few drops of water and mix well with a spoon. Dip the swab into the lemon juice. Then use the swab to write a message on ordinary white paper. When it dries, the writing will be invisible. When you want to read the message, heat the paper by holding it near a light bulb.

What happens: The words appear on the page.

Why: The juice of lemons and other fruits contain compounds of carbon. These compounds are nearly colorless when you dissolve them in water. But, when you heat them, the carbon compounds break down and produce carbon, which is black."

What happened when CKS tried it? My message didn't show up that much - it was clear and shiny and I could hardly see the letters. My mom used a lot of lime juice and it showed up well and it was a little yellow, but some other letters were clear. My advice when you try this is: Use a lot of lemon juice or lime juice to make this work.

CKS rating: 4 stars - Pretty fun!