Convection Currents

What do these three things have in common?

All of these amazing forces of nature are powered by convection – changes in temperature and density of fluids that create movement. Sounds pretty complicated. But here’s a simple experiment you can do to see convection in action!

What you need: A medium-to-large clear storage tub (or any sort of large clear container), blue and red food dye, and lots of water.

Steps:

  1. A couple days ahead of time, make some blue ice cubes by just freezing some blue colored water.

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2. When the blue water has frozen into cubes, fill the tub about halfway with room temperature water. Let the water settle so it’s smooth and calm.

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3. Carefully add some blue ice cubes to one end of the tub. You’re practically guaranteed to stain your hands blue. Be careful not to bump the tub or the surface it’s sitting on!

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4. Carefully pour some red food dye into the other side of the bin. Again, be careful to not bump your experiment!

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5. Watch how the different colors move around within the water. Where does the blue dye go as the ice melts? Where does the red dye go? Do they mix right away? How do the colors interact?

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Does the red float on top of the blue? Do the red and the blue swirl around each other and mix? You have just created your own convection cell!

 

What’s going on here?

Convection is basically just a fancy word for heat transfer. Heat is a type of energy, which cannot be created or destroyed – only moved. When the ice is added to the room temperature water, it starts to melt, but the water that melts out is still very cold. The cold water is more dense than the room temperature water and red food dye. Remember, density refers to how many molecules are packed into a certain amount of space. Because the cold water is more dense, it’s heavier, so it sinks to the bottom. But as the cold water from the ice gets warmer in the tub, the water molecules spread apart again. It becomes less dense and lighter, so it rises back up. This circular motion is called a convection cell.

from Wikipedia: convection

You find convection cells in all kinds of fluids, or substances that take the shape of their container. A fluid can be a liquid or a gas. When you have huge amounts of a fluid, for example, an ocean or the atmosphere, you have lots of convection cells. The denser, colder, heavier air or water sinks down, and rises as it gets warmer. Large convection cells working together create massive convection currents, like major ocean currents or air currents. These are sometimes called conveyor belts.

from Wikipedia: climate change

The air in our atmosphere is also a fluid, and different air temperatures lead to convection cells in the air. When hot air rises off the ground quickly, it leaves behind an area of low air pressure. Colder air, which dense and heavy, rushes in to fill the low pressure area. We feel that all the time – we call it wind! But when those convection cells in the air move really fast, that can create storms. Those can be small summer thundershowers or massive hurricanes.

from Wikipedia: prevailing winds

So what about volcanoes? What do they have to do with convection? Well, the earth’s crust is divided into sections called tectonic plates, which float on top of a layer of hot magma, or molten rock, called the mantle. The mantle is also a fluid, with warmer, less dense areas and cooler, denser areas. These circulate in massive convection currents. The tectonic plates float and move (very slowly) on top of these currents. Volcanoes form mostly at the edges of tectonic plates, where hot magma is pushed out in the form of lava. The lava is pushed out of the earth by the force of convection!

from Wikipedia: mantle convection

Fun Fact: Some air currents, or convection cells, are so stable and long-lasting that they’ve been named. These massive convection cells are caused by the spinning of the earth! The northern trade winds blow northeast to southwest above the equator, so many European explorers used them to sail to the Americas. The strong winds that whip around the edges of Antarctica are known as Westerlies because of their direction. I was out flying my kite in the southern Westerlies just the other day!

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Special thanks to Kalyani, who helped with photos and cleanup for this experiment.

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Hovercraft Hijinks

In sci-fi movies, there always seem to be little ships and transportation devices that simply float along and zoom anywhere with no wheels. Did you know that there are real vehicles that can do that? They’re called hovercrafts, and they can travel over just about any surface – even water! Here’s how you can build your own little tabletop hovercraft.

What you need: a balloon, a pop-up bottle top (like from a water bottle or a dish soap bottle), an old CD or a thin plastic margarine lid, a hot glue gun or superglue, scotch tape, a thumbtack, and a friendly adult helper. If you’re using a plastic lid, you’ll also need scissors.

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Steps:

1. If you’re using a plastic lid, ask your friendly adult helper to cut a small circle out of the center of the lid, about 2 cm or 1 in across. If you’re using a CD, it already has a hole in the center, so you can skip this step.

2. Cover the hole in the CD or lid using several strips of scotch tape.

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3. Use the thumbtack to poke about 10 small holes through the tape.

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4. Ask your friendly adult helper to help you hot glue the bottle cap to the CD or lid, directly over the hole in the center. Be careful not to burn yourself!

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5. Allow the glue to dry and cool off. Make sure the bottle cap is closed.

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6. Blow up a balloon, but don’t tie it off! Twist the mouth of the balloon so the air won’t leak out.

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7. Stretch the mouth of the balloon over the top of the bottle lid. You may need a helper for this! Make sure that the lid is in the closed position, then let the balloon untwist.

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8. Once the balloon is securely on the bottle top, set your hovercraft on a smooth surface. Pop open the bottle top.

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9. Watch how the CD or lid glides across the floor, counter, or table!

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Note: You may need to poke extra holes in the tape if your hovercraft doesn’t move quite as smoothly as you’d like it to.

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That’s me, the blogger, by the way. Hello!

What’s going on here?

When you pop open the bottle top, the air trapped in the balloon is let out slowly through the pinholes in the tape. The air flowing out creates a sort of cushion underneath the disk that allows it to hover slightly. The air cushion reduces friction between the disk and the surface it’s sitting on. Friction is the force that makes objects stay in place. If you push a box along a carpeted floor, it resists because there’s a lot of friction between the box and the floor. But if you put wheels under the box, or you push the box on a smooth hardwood or linoleum floor, you reduce the the friction between the box and the floor, and it doesn’t resist as much. You can also feel friction as heat if you rub your hands together really fast, or rub your arms to get warm when you’re cold!

from Wikimedia Commons

The hovercraft we built here was small, but many are huge! They’re used to transport all sorts of things over land, water, mud, sand, ice, and more. Usually these bigger hovercrafts are fitted with a flexible skirt around the bottom, to keep more air trapped beneath the vehicle and to make it easier to get past small obstacles. The air outside the vehicle is under atmospheric pressure, or the weight of the atmosphere (about 15 pounds per square inch at sea level). But the air pumped underneath the vehicle is under more pressure, which pushes the vehicle up and generates lift. This boat below is a very large hovercraft. The massive fans on the back push air down beneath the boat to keep it hovering above the water.

from user Chris Parfitt at flickr.com

Fun Fact: Ever played air hockey? An air hockey table is basically like an upside-down hovercraft. The surface of the table is nice and smooth, and it’s covered in tiny pinholes that shoot out little jets of air. The whole point of the table is to reduce friction as much as possible. The puck and the mallets are floating on air!

from Wikimedia Commons

Special thanks to Hannah, who provided the hot glue gun and helped take photos of the build.

Eyes on the Sky

What do you think is the oldest kind of science? Chemistry? Biology? Physics? Those fields go back hundreds of years, but none of them match astronomy, the study of outer space. People have watched the sky and wondered about the stars for thousands of years. The first astronomers were the ancient Greeks, about 4,000 years ago.

from Wikipedia: Orion (constellation)

The ancient Greeks named many constellations, or patterns of stars, after their mythical figures. Some of these include the hero Hercules, the queen Cassiopeia, and the hunter Orion who is always pursued across the sky by the giant scorpion.

By watching the stars and observing their positions, the Greeks and many others saw that the stars appear to move around the earth. For a long time, people thought that the Earth held still while the sun, moon, stars, and other planets revolved around it.  Now we know that the Earth and the planets go around the sun, and the stars are very far away. The sun and stars “move” because the earth is revolving around the sun, and rotating on its axis.

But if you were just watching the stars, you might think that the earth is still and the stars are moving. Here’s how you can build a neat tool called an astrolabe that will help you keep track of how the stars “move”.

What you need: Cardboard or stiff paper (I used an old cereal box), scissors, a protractor, a marker, tape, a piece of string, and some sort of weight like a washer (I used a couple screws).

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Steps:

  1. Use the scissors to cut out a piece of cardboard in a shape like this, just a little wider than a quarter of a circle:

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2. Line up the protractor along one edge of the cardboard shape, with the center point of the protractor (there’s usually a little hole there) on the corner. Draw a mark every ten degrees, from 10 to 90, like this:

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3. Use the flat edge of the protractor to draw lines connecting the small marks with the corner of the cardboard, like this:

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4. Label all your degree lines: 10°, 20°, all the way up to 90°.

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5. Tape the straw to the edge of your paper, just above the 90° mark. If you’re using a bendy straw, you’ll need to cut off the the bendy part so you can see straight through the straw.

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6. Tie one end of the string around the straw, just in front of the corner where all the degree marks join.

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7. Tie the other end of the string around some sort of weight – washers, nuts, bolts, and screws will all work.

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8. Your astrolabe is complete! Now just wait for it to get dark so you can see the stars.

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How to use your astrolabe:

Once it’s dark, go outside and find a star in the sky. Pick one that’s easy to find, like one that’s part of a constellation. Look at the star through the straw on your astrolabe, and then hold the string in place with your thumb and forefinger. Remember or write down where your string is.

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Wait a few hours, then come back and find the same star again. Look through the straw at the star from the same place. Pinch the string to mark the new angle of the star. Compare that to the angle you found earlier. You’ll see that the star is in a different position!

People used astrolabes of all shapes and sizes for hundred and hundreds of years to see how the stars moved. Often sailors used them to find their position at sea. They knew certain stars would be in particular places at certain times of the year, so they could find their own location on the earth (without GPS!) by learning the positions of the stars.

from Wikipedia: astrolabe

What’s going on here?

The earth rotates on its axis, and it completes a rotation every 24 hours. That’s what a day is! As the earth spins, the sun comes into view, or rises, and goes out of view, or sets. The same thing happens with the stars! When your part of the earth is pointed away from the sun, it gets dark and we can see stars. You can’t see stars during the daytime because our own star, the sun, is so bright that it blocks out anything else.

from nasa.gov

The earth also revolves around the sun, and it completes a lap every 365 days. That’s where we get the length for a year! The tilted axis always points the same direction, which means that you can see stars in different directions at different times of the year. For example, you can see the hunter Orion, but not the giant scorpion, during the winter in the northern hemisphere (the upper half of the planet), and in the summer in the southern hemisphere (the lower half). Then in the northern summer and the southern winter, you can see the the giant scorpion, but not Orion. 

from nasa.gov

Tips for stargazing:

Red-LED-torch smallvers 261
from scopesnskies.com

First, you’ll need a clear night, and you’ll need to be away from bright lights like from a building. It’s better for stargazing when the moon is new or a very thin crescent. The brighter the moon, the harder it will be to see stars around it! The best way to see a lot of stars is to let your eyes adjust to the dark. The longer you look, the more stars you’ll be able to see! Avoid getting bright light (like from car headlights, flashlights, or phone screens) in your eyes. Use a flashlight with a red beam option – that won’t mess up your night vision.

You can use a star chart to identify constellations – many glow in the dark! You can use a telescope or binoculars to look closely at planets and into the Milky Way. The stars you see will depend on the time of year and where you are. Sometimes you can see a lunar eclipse: the shadow of the earth cast upon the moon by the sun. At certain times of year, the earth passes through areas where there’s a lot of debris. The debris is drawn to the earth with gravity, but usually burns up in the atmosphere, which creates meteors or shooting stars. The best meteor shower is called the Perseids, which happens around August 12.

from nasa.gov

Fun Fact: There is one star in the sky that does not appear to move, like in the long exposure picture below. It’s called Polaris, or the North Star, and it’s almost directly above the North Pole (so it’s only visible from the northern hemisphere). All the other stars appear to go around it. Sailors and many others used Polaris to navigate, because it’s always due north. But in about 12,000 years, it won’t be directly over the North Pole anymore. That’s because the axis that runs through the center of the earth wobbles a little bit, like a spinning top.

from user Darron Birgenheier on flickr.com

Special thanks to Hannah for demonstrating the use of the astrolabe!

Make your own Lava Lamp

Everyone loves lava lamps. I’ve never met anyone who doesn’t like them. They’re fascinating to watch, and they are absolutely essential to the complete bachelor pad.

from user Dean Hochman on flickr.com

With this awesome experiment, you can make your own version!

What you need: a tall clear bottle, water, food dye, vegetable oil or canola oil, and fizzing tablets like Alka-Seltzer (I’m based in New Zealand, so I used these Aspro-Clear pain relief tablets). A funnel is helpful but not necessary.

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Steps:

  1. Pour about 4 cm or 2 in of water into the bottle.

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2. Fill the rest of the bottle with veggie oil. This is where the funnel comes in handy! What happens when the oil meets the water?

3. Add several drops of food dye. Aim the color right at the middle of the surface of the veggie oil. How do the drops of dye behave? Does the color mix with the oil?

4. Squeeze the bottle and tap it against your table or counter to make the drops of food dye mix in with the water at the bottom of the bottle. You can even use a straw or a long stick to mix the color into the water.

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5. Once the color has spread through all the water, remove 2 fizzy tablets from their packaging. You’ll probably need to break them in half so they’ll fit through the neck of the bottle. Drop them into the bottle.

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6. Enjoy the show! Watch how the fizzy tablets affect the the colored water in the oil. To really make this look like a lava lamp, you can put a flashlight underneath it.

What’s going on here?

First, the water and the oil don’t mix together. The water is what we call polar, meaning that each water molecule, like the one below, has a positive region and a negative region, just like how a magnet has a north and a south.

from Wikipedia: chemical polarity

Oil, on the other hand, is nonpolar. Its molecules don’t have a negative side and a positive side. Polar liquids mix together, and nonpolar liquids mix together, but they don’t mix with each other very well. That’s why you have to shake up salad dressing before you put it on your salad. That’s also why it’s hard to simply rinse oil off things with water – you need soap to break it down and wash it away.

Second, the oil has less density than the water. Density refers to how much material fits into a certain amount of space. A brick is more dense than a wad of bubble wrap. In this case, a teaspoon of water has more molecules than a teaspoon of oil. It’s the same amount, but the water is denser than the oil. So the oil floats on top of the water. That’s why you see those rainbow oil slicks floating on top of puddles on the road when it rains.

from gettyimages.com

As for the food coloring, the dye is both polar and more dense than the oil, so drops of dye float right through the oil without mixing in. But it does mix with the polar, dense water.

Third, when the tablets hit the water, they start fizzing and releasing gas bubbles. The bubbles travel up because the gases inside are lighter and less dense than either the water or the oil. So they go all the way up to the top of the liquid and then burst, releasing the gases. Soda is fizzy for the same reason – carbon dioxide gas is trapped in the bottle or can, and when you open it, the gas is released in bubbles traveling up to the surface. If you drink the soda too fast, the gas might might try to go out through your nose or come out as a burp. As the bubbles travel up, they carry a little bit of the colored water with them, which creates the lava lamp look.

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Fun Fact: Of all the elements (the most basic substances that make up the universe) the most dense is called osmium. Osmium (top left) is a metal very similar to platinum, but it’s too brittle to be used for much of anything. Other very dense elements include gold (top right), lead (bottom left), and mercury (bottom right). Liquid mercury is so dense that you can float heavy coins on it!

all four images from Wikimedia Commons

Carnation Conundrum

When you water a tall tree, you only sprinkle water on the roots. You can’t reach the leaves. But somehow, the water you give your tree still reaches those leaves all the way at the top! How does that happen?

With this cool two-part experiment, you can learn how plants move water and nutrients around, and at the same time, make some really pretty and interesting flowers!

What you need for Part 1: White carnations (or roses, but be careful of the thorns), bottles or tall thin vases, water, food dye, and scissors.

For Part 2, add: 2 identical medium cups or glasses, a sharp knife or razor blade, and a friendly adult helper.

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Steps for Part 1:

  1. Pour about 4 cm or 2 inches of water into each bottle or vase.

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2. Add a lot of food dye to each bottle. The colored water needs to be dark and intense! I made my first bottle bright yellow-orange (a lighter color), my second bottle blood red (a medium shade), and my third bottle a super-dark purple.

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3. Use the scissors to cut off the bottom of a flower stem. With carnations, it’s best to cut them right on one of the wider “knuckles”. I had to cut off a lot of stem so my flowers would stand up in their bottles.

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4. Immediately place each trimmed carnation into a bottle. Then put them somewhere where they won’t be disturbed for a couple of days.

5. While you wait, make predictions! What do you think will happen to the carnations? Will the entire flower change color? Will there be splotches of color here and there? How long do you think it will take for some sort of change to take place?

Steps for Part 2:

  1. Set up your two glasses side-by-side, close enough to touch each other, and pour about 2 inches or 4 cm of water into each glass.

2. Add two different colors of food dye to each glass. Make sure the colors are really dark and intense!

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3. Use the scissors to cut off the end of the stem. Again, the best place to cut is at one of the thicker spots on the stem.

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4. Ask your friendly adult helper to use the knife or razor blade to carefully split the stem from the bottom. Don’t cut apart the entire stem! About 15 cm or 6 in from the bottom will do it.

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5. Very gently pull the two halves of the split stem apart – you don’t want to tear a piece off by accident! Be sure to thank your friendly adult helper.

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6. Carefully place the carnation with the split stem into the two glasses with different colors – one half of the split stem in each glass. Note: It’s best to set this up in the same place you’ll let it sit for a few days. It’s hard to move it around!

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7. Let the split stem flower sit for a couple of days. Come back and check on it every so often, but don’t disturb it! Will the green and blue mix together?

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After a few hours, the colors should start to appear in the carnation petals!

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After a day or two, the colors will be nice and bright. Where do the colors show up? How bright are they compared to the colored water? How did the colors get all the way up to the flowers?

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What’s going on here?

First, let’s take a look at a microscope cross-section of a plant’s stem:

from wesharepics.info

See those big holes around the edges? Those are channels called xylem and phloem, and they make up the plant’s vascular system, or how water and nutrients move around the plant. The channels run all the way up the stem, and then branch out into smaller channels in the leaves and flower petals. It’s a lot like our own circulatory system, or blood vessels. You can see the channels really well in something like celery (you can also do this experiment with celery, but the flowers are prettier).

from Wikimedia Commons

So how does the water you give a plant travel UP, against gravity? The channels that transport water, the xylem, are very thin tubes. Water molecules like to stick together, using what we call surface tension. The thin tubes combined with the water’s surface tension allow the water molecules to “climb” up the stem and out to the leaves and flowers. The food coloring simply allows us to see how the water travels!

 

Fun Fact: There are four categories of land plants on Earth: mosses, ferns, evergreens, and flowering plants. Mosses (top left) have no seeds and no vascular system. Ferns (top right) are more developed and have a vascular system, but no seeds. Evergreens (bottom left) have a more primitive type of seed commonly known a pine cone. Flowering plants (bottom right) have fully developed seeds, complex vascular systems, and often produce fruits to help distribute their seeds.

all four pictures from pinterest.com

Note: Special thanks to Emily, who helped me out with taking photos for this experiment.

Bartholomew and the Non-Newtonian Fluid

Dr. Seuss is fantastic. I grew up on his books. Two of my favorites were The 500 Hats of Bartholomew Cubbins and its sequel: Bartholomew and the Oobleck. Greedy King Derwin of the Kingdom of Didd wants something new to fall from the sky. So his magicians invent OOBLECK. The strange green sticky stuff falls from the sky and chaos ensues!

Copyright Theodore Seuss Geisel, 1949

You can make your own oobleck quite easily. You don’t need anything fancy, and the slime is a lot of fun to play with!

What you need: cornstarch or corn flour (they’re the same thing), water, a large bowl, food dye if you want colorful slime, and paper towels (because this is really messy!)

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Steps:

1. Start by just picking up some cornstarch in your hand. What does it feel like? What does your skin look like after the cornstarch has touched it?

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2. Pour just a little bit of water into your hand with the cornstarch. What happens? What does it feel like? Can you squeeze the goop that forms?

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3. Pour a bunch of cornstarch into the bowl.

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4. Add water to the cornstarch SLOWLY. Keep checking it and don’t add too much liquid! You want it to be pretty thick and slightly “chunky.” I mixed green food dye to my water so my oobleck would be green like in the book, but the color got pretty diluted.

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5. Stick your hands in the bowl and play around with the goo! Can you pick it up and roll it into a ball? What happens if you push on it fast or slow? Does it swish around the bowl like plain water would?

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6. To clean up, dump the oobleck directly into the trash or into your garden (it’s just cornstarch and water, so it won’t hurt the environment). DO NOT dump it down the drain! You’ll clog it up. After you’ve gotten rid of most of the oobleck, you can just rinse off the rest.

 

What’s going on here?

The cornstarch is a very fine powder, which is why it can get into the grooves of your fingerprints. When it’s mixed with water, it form a type of liquid known as a non-Newtonian fluid. Sir Isaac Newton described liquids flowing and taking the shape of their containers. The molecules move apart when an object intrudes, which is why you swim instead of sitting on top of the pool.

But some liquids, like oobleck, don’t follow the same rules as most liquids. The fine cornstarch particles float in the water, but when they encounter pressure, like from your hand squeezing it, the particles bunch together and form a solid. It’s kind of like pushing against a mound of sand: the little sand particles move out of your way if you push slowly, but if you push fast the sand gets bunched up and compressed. So when you quickly pick up a handful of oobleck, it’s a solid mass. But as you just hold it, the particles float in the water again, and it slowly drips out of your hand.

from Google Site: The Smartest Materials

In other words, oobleck is both a liquid AND a solid, depending on how you interact with it. Silly Putty is another non-Newtonian fluid, but it’s a lot thicker than oobleck. You can mold it like clay, but if you hit it with a hammer, it will shatter. Some military researchers are even researching ways to use non-Newtonian fluids to protect soldiers against impacts like bullets!

 

Fun Fact: If you have enough cornstarch and water, you can mix them up and “walk on water” if you move fast enough! (Although some might consider that cheating.) The Mythbusters demonstrated this in their first Ninja Special episode (2007):

 

Note: Special thanks to Guy and Mari, who helped me out with this experiment!

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Not the Old Volcano Experiment

Everyone knows that old favorite volcano experiment. Build a mountain out of clay, put a pipe in it, pour in baking soda and vinegar, and watch the eruption! But there are a lot of other cool things you can do with baking soda and vinegar. You can even use these two awesome ingredients to fill a balloon!

What you need: A bottle with a narrow neck (I used the original vinegar bottle), a balloon, a funnel (you can make one out of paper if you don’t have one), baking soda, and vinegar.

Note: I poured out most of my vinegar into a glass so I could use a little bit of vinegar in its original bottle, but I could still have some vinegar leftover afterwards.

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Steps:

  1. Set up your bottle so it has about 2 centimeters of vinegar in it.

2. Use the funnel to pour some baking soda into the balloon.

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3. Carefully stretch the mouth of the balloon over the neck of the bottle.

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4. Gently lift up the balloon so that the baking soda inside falls out into the vinegar bottle.

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5. Watch how the baking soda and vinegar react with each other. What happens to the balloon? Why?

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What’s going on here?

First, the vinegar and baking soda react together like that because the vinegar is a weak acid called acetic acid, and the baking soda is a base called sodium bicarbonate. Acids have a high pH, from 8 to 14, while bases have a low pH, from 0 to 6. Water has a pH of 7, which is considered to be neutral. When the base in the baking soda meets the acid in the vinegar, they react together and fizz. Their molecules break apart and then come together to form different materials in a chemical reaction, like this:

from makerspace.com

Some of the carbon and oxygen from the reaction combine to form a gas called carbon dioxide. Our bodies produce carbon dioxide – it’s what we breathe out. The carbon dioxide gas fills the balloon, just like how you fill a balloon when you breathe into it!

 

Fun Fact: You can use baking soda and vinegar to clear out a clogged drain! Simply pour some baking soda into the drain, and add some vinegar. They’ll fizz up and remove the blockage. But it can also be dangerous to mix certain acids and bases. For example, you can clean with bleach (a strong acid) OR with ammonia (a strong base) but you should NEVER combine them! They’ll form a toxic chlorine gas. Carbon dioxide can also be dangerous in large amounts, but this experiment produced a small, harmless amount of it.

Note: Special thanks to Hannah, who has helped me conduct several experiments!

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Peeps Jousting

Now that Easter has passed, what are we going to do with all those leftover stale Marshmallow Peeps? Here’s a fun experiment you can do to use those peeps and have some fun! You can also do this with regular marshmallows. Double check with an adult before you do this experiment!

What you need: 2 marshmallow peeps (or just regular marshmallows), a paper towel or paper napkin, a microwave, and 2 toothpicks. I used a couple of wooden skewers leftover from the rock candy experiment, and broke them in half so they’d be the right size.

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Steps:

  1. Insert the toothpicks into your peeps or marshmallows so it looks like they’re holding spears. The bird shape peeps work best for this, but bunnies will work too.

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2. Set up your peeps so they’re facing each other, like in a joust. Place them upright on the paper towel, in the microwave.

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3. Set the microwave for 45 seconds or so. No longer than 1 minute!

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4. Watch what happens to the peeps! This is called Peeps Jousting because both will expand, and one’s toothpick will pop the other one first. Which one will win?

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5. You can eat the gooey marshmallow mess afterwards! Be careful not to burn your tongue – allow the marshmallow to cool for a few seconds.

Safety note: NEVER put anything metal in a microwave! You’ll have sparks and possibly a fire. For this experiment, stick to wooden skewers or toothpicks. Do NOT use anything like needles or a paperclips for your spears.

 

What’s going on here?

This is all about how microwaves work. When you turn on a microwave oven, your food is heated up. What’s happening is that the machine is shooting out a kind of electromagnetic wave. There are all kinds of electromagnetic waves, including radio waves, infrared, all the visible light and colors we can see, ultraviolet rays, and x-rays. They behave the same way that waves in water act.

from nasa.gov

Microwaves are long and slow waves, compared to visible light and x-rays. But they move through the matter inside the microwave oven, and make the molecules move up and down. This is called agitation. As the water molecules in your food get agitated, they move around more, spread apart, and become warmer. That’s why your food becomes warm!

The marshmallow is made of sugar and gelatin. Gelatin has lots of water in it, so the water molecules vibrate and spread out. The other ingredients in the marshmallow don’t block the water molecules at all, so they continue to expand. That’s why the marshmallow puffs up! The toothpick can then “pop” the surface of the other marshmallow as it expands.

from cigarweekly.com

Fun Fact: The smaller a type of electromagnetic wave is, the more easily the wave can pass through matter. Radio waves are very long and very slow, so they can’t travel through much, which is why you can lose your radio signal in your car if you drive between the radio tower and a big building. Ultraviolet or UV rays are much smaller and can burn your skin if you don’t have on sunscreen or protective clothing. X-rays and gamma rays are the smallest and most dangerous. If you have to get an x-ray scan at the hospital, you have to use a sheet of lead, which is very dense and heavy, to protect the parts of your body that aren’t being examined. This cool kid is protecting her eyes from UV!

from user Boudewljn Berends at flickr.com

Rock Candy

Science is a lot of fun, but it can be dangerous sometimes too. People will tell you “don’t eat this,” or “don’t sniff that,” or even sometimes “don’t touch this.” There’s a really good reason for that – you could get hurt or breathe in something toxic. But with this cool experiment, you can eat the results – and it’s delicious! But there are some dangerous parts in the process, so make sure you have a friendly adult to help you out with this one.

What you need: a friendly adult helper, water, sugar, a saucepan, a wooden spoon, a stove top, a glass, a wooden stick (like a skewer), and a clothespin. You can substitute the wooden stick and clothespin with a pencil, a piece of string, and a weight (like a clean metal washer). You can also add food coloring if you want your rock candy to be colorful.

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Steps:

  1. Measure 1 cup of water and pour it into the saucepan.

2. Ask your friendly adult helper to put the water on a boil.

3. When the water is boiling, slowly and carefully add 2-3 cups of sugar to the water. DO NOT dump in all the sugar at once! I mixed in 1/4 of a cup at a time. Be sure to mix in the sugar with the spoon until all of it has dissolved into the water.

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4. Keep adding sugar, a little bit at a time, until no more sugar will dissolve in to the water. As you add more sugar, it will take more time and more stirring to get it to dissolve, so be patient!

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5. Ask your friendly adult helper to take the sugar water off the heat, and allow the mixture to cool for about 20 minutes.

6. Have your friendly adult helper carefully pour the sugar water mixture into a glass until it’s almost full. A funnel comes in handy here!

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7. Pinch a wooden skewer in a clothespin, and then use the clothespin to suspend the stick in the glass of sugar water so it’s not touching the sides or bottom of the glass.

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8. Add several drops of food dye to the sugar water if you want your rock candy to be nice and colorful! But it’s just as tasty if it’s not colored.

9. Carefully place your glass somewhere where it won’t be disturbed, and let it sit for about a week. It’ll be tempting, but don’t mess with it!

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10. After a week has passed, sugar crystals should be forming on the wooden stick. Carefully remove the stick from the glass and you’ll have your own rock candy!

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A few notes:

You can do this experiment with a piece of string instead of a wooden stick. Tie one end of the string to a pencil, and the other end to something heavy like a clean metal washer or a screw. Set the pencil across the top of the glass and let the string and weight hang down into the glass without touching the sides.

from sciencebuddies.org

In my experiment, I didn’t actually manage to grow candy crystals on the stick. Instead, they grew on the sides of the glass. My final product was bought, not grown myself. It’s really important to remember that science doesn’t always work! It can be hit-or-miss. If your experiment doesn’t work, don’t give up! Learn from your mistakes. A lot of what we know comes from trial and error. In fact, Thomas Edison tried over a thousand different methods to make the light bulb work before finding a solution.

 

What’s going on here?

When you mix very hot water with sugar, the crystals that make up the sugar dissolve, and mix together with the water molecules. This is called a saturated solution. When you add so much sugar that the hot water can’t dissolve it anymore, it becomes supersaturated. As the water cools down, the the sugar molecules come out a solid again. In chemistry, when a solid comes out of a liquid mixture (or a solution), it’s called a precipitate. As the sugar water cools and sits, the sugar crystals form a solid precipitate on the wooden skewer or string.

from ontariosciencecentre.ca

The solid sugar crystals then make up a surface for more sugar crystals to form. That’s how the solid mass of the rock candy comes together. This is what sugar crystals look like up close:

from user ViataVerdeViu on pinterest.com

Also, the water evaporates over time, leaving more and more of the sugar behind. The sugar solution becomes even more supersaturated!

 

Fun Fact: The very first sugar candy was made in India around 250 C.E. (or A.D.). The earliest candy of any kind goes all the way back to ancient Egypt, where people would mix honey with fruits and nuts for a sweet treat!

Cream Clouds

Why does it rain? How does water just fall from the sky? Do this fun, colorful experiment to learn more.

What you need: A clear container (like a glass) of water, shaving cream, and food coloring.

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Steps:

  1. Spray shaving cream on top of the water in your glass. Don’t make it too thick!

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2. Drip drops of food dye directly on top of the shaving cream. Wait a few minutes.

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3. Watch the food coloring seep through the shaving cream. Eventually, gravity will make the food dye travel all the way through to the water beneath.

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4. Watch how the food dye “rain” falls from the shaving cream “cloud”!

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What’s going on here?

This experiment beautifully shows one of the important parts of the water cycle. All of the water on earth is constantly recycled, through three key processes: evaporation, condensation, and precipitation.

Imagine you have a lake. The sun comes along and heats up the water, and some of it evaporates, or becomes a vapor or gas. The vapor rises into the atmosphere, where it’s very cold. The cold air makes the water vapor condense, or turn back into a liquid. But the water doesn’t condense all at once. Liquid water gathers with water vapor in what we call clouds. Clouds carry along the liquid water until there’s too much for the cloud to hold – then it spills out as rain or snow, or precipitation.

In this experiment, the shaving cream was like a cloud, and the food dye was like the liquid water held in the cloud. But eventually the coloring wasn’t held up by the cloud anymore, and so it “rained” out into the water in the glass. The food coloring was the precipitation!

 

Fun Fact: Ye Olde sailors used to predict weather patterns based on the types of clouds they saw. For example, one of the common sailor sayings was, “Mackerel skies and mares’ tails make tall ships carry low sails.” That means that when the clouds looked like fish scales (mackerel skies) and thin wispy horse tails, it meant that a storm was likely, and the ship would have to drop down her sails so she could stay her course during the blow.

from sailingred.com