A homopolar motor is a device that relies on flowing electricity, magnetic fields, and the interaction between the two. It consists of a voltage source, neodymium magnets, and a conductor that allows electricity to flow. And it’s super easy to make yourself!
What you’ll need:
1 AA battery
2 neodymium magnets
Thick copper wire
Place one of your magnets onto the positive terminal of the battery.
Use the already attached magnet to test the poles of the second magnet. Figure out which sides are repelling each other, and place the second magnet so that the repelling side faces away from the battery. This way, either both South poles or both North poles are facing outwards! (Note: it doesn’t matter which, as long as they’re consistent with each other!)
Shape your copper wire so that it can hook easily on the inside of the magnets. Try to maximize the amount of contact it has with the magnets on BOTH sides, so as much electricity as possible can flow. When it’s been properly shaped, hook the wire onto the motor!
Instead of using a wire, you could use a sheet of aluminum foil! Lay it as flat as you can on a level surface, away from any metals that might attract your magnets. Make sure there are no tears or holes in the aluminum. Then place your battery-magnet motor on top! The aluminum will allow electricity to flow!
When a magnetic field is applied to an object carrying electricity, it applies a force to that object. This is called the Lorentz Force. Due to the electricity flowing through the magnets, this force becomes a torque, causing the motor to rotate and drive forward!
Water is usually pretty predictable. At standard pressures it will boil at 100˚C and freeze at 0˚C. However, under special circumstances it might surprise you. Dihydrogen monoxide can become supercooled, dropping below 0˚C while maintaining the liquid phase of matter.
Acquire distilled or purified water.
Fill an empty bottle with tap water (this is your control).
Place all three bottles in the freezer at the same time
Leave them in for roughly 2 hours (if all of the water was originally at room temperature)
The timing of this will vary with each freezer. After the first hour, check on the bottles periodically to check for signs of freezing.
The bottle filled will freeze before the purified water. At this point you will know that the purified water is below zero, and is ready to be removed from the freezer.
Take it out, give it a hard slam on the table, and watch the H2O turn from liquid to a solid right in front of your eyes!
The liquid will flash freeze into a solid. By hitting it on the table, the water molecules are bumped into alignment in a more crystalline structure, typical in solid ice. This induces a chain reaction that you can follow all the way down the bottle!
Have you ever really sat down to think about how much space there is in the universe? It’s pretty inconceivable, but there are some useful tools that can help put things in perspective. You’ve already seen a scale model of our solar system by mass, so here is a model of the space between our planets that can fit in your pocket!
What you need:
Long strip of paper
First, cut a strip of paper long enough that it roughly spans the distance of your arms. Then, have a marker handy to be ready to indicate where each planet will lie.
Label one end of the strip as the sun and the other as Pluto/Kuiper belt.
This will show the full distance between the sun and the outer reaches of the solar system.
Fold the paper in half and crease it. That line is for Uranus, it is roughly halfway between Pluto and the sun!
Fold it in half again (it should now be in quarters). The crease between Uranus and Pluto is for Neptune.
The crease that is between the sun and Uranus is for Saturn.
Now fold the sun to Saturn and mark Jupiter in that crease.
We have completed all of the gaseous outer planets, meaning that all that is left are the rocky inner planets, which fit between the sun and Jupiter!
Fold the sun to Jupiter and label it as the asteroid belt, the area in our solar system where some of the largest known asteroids live.
Now fold the sun to the asteroid belt. This is where Mars goes.
We will complete the remaining three planets in the last step.
Fold the sun to Mars, then fold in half again. Closest to the sun is Mercury followed by Venus, then Earth.
Take a look, roll it up, and there you have it! A basic scale model of the distances between the planets of our solar system that can fit in your pocket. Would you have been able to guess how much space there is relatively between our planets? Did any of the spacings surprise you?
An electric motor is a device used to convert electrical energy to mechanical energy. Electric motors are extremely important in modern-day life. They are used in vacuum cleaners, dishwashers, computer printers, machine tools, cars, subway systems, sewage treatment plants, etc, and you can make your own at home! Here’s how:
Coil the wire around a battery about 30 times. Wrap the extended ends of the wire through the coil, securing the coils in place.
Carefully file the enamel off of the bottom half of the extended portion of the wire.
Secure one wire post to each end of the battery, creating a small U-shape to cradle the coil.
Slide a magnet onto the battery.
Place the coil onto the posts and give it an initial spin!
Electricity will flow from the battery through the coil of wire. Moving electricity induces a magnetic field in the coil, which opposes the magnet half of the time, and is attracted the other half. Give it a flick and watch the electrical energy from the battery be converted into the mechanical spinning you see!
Kinetic sculptures are moving art pieces, that usually do not have a motor, but alternatively use other forms of energy to propel the movement. Wind, water, or an initial manual push are common types of energy which kinetic sculptures harness. The art piece that we are going to make is going to harness energy given off from a flame.
What you need:
Cut a spiral in the piece of construction paper.
Secure your skewer with the clothes pin perpendicular to the table and lightly place the center of the spiral on the point.
Place the tea candle on the clothes pin, under the spiral, and light it.
The flame heats up the air around it. Since hot air is less dense than cold air, it rises. The air current flowing pass the spiral will push it, causing it to spin. There you have it, an easy DIY kinetic sculpture, harnessing energy to make moving art. What awesome science-art pieces can you come up with?
Geodes, seemingly ordinary rocks hiding pockets of crystals inside, have fascinated amateur geologists for centuries, but did you know you can make your own geodes with just what’s in your kitchen?
Something to hold the eggs (a piece of the carton works well for this)
Water-soluble solid (salt, sugar, baking soda, etc.)
Crack eggs as close to the narrow end as possible to save as much shell as you can
Heat water to nearly boiling and pour it into the egg, cooking the membrane inside so you can remove it. (if you don’t remove the membrane, it will mold and turn the crystals black)
Bring your water to a boil in the saucepan, gradually adding about half as much salt by volume as you have water
Keep adding salt until no more dissolves into the water
Add the mixture to your eggshells
Add the food coloring to each egg
Wait a few days for the water dissolve
Admire your results
So how does this exactly work? When you’re boiling the water, you’re adding energy to it in the form of heat, allowing it to dissolve more of the solid than it normally would. At this point, there’s so much solid (in our case salt) dissolved in it that there’s nearly no space left between molecules. This now “super-saturated” solution gradually loses energy as it cools down, forcing the solid out of solution slowly. This slow release allows the solid to instead build a growing network of crystals inside and outside the eggshell. This is actually a similar process to how geodes form in nature: water with dissolved minerals seeps into air pockets inside rocks, slowly depositing the minerals as the water flows through the rock. Try it for yourself!
The relationship between electricity and magnetism is as old as space and time, but is a complicated one. As light propagates, electricity and magnetism flow in and out of each other, forever connected. This connection can allow for some pretty interesting phenomenons in physics.
Due to induction, we can get the “train” to propel forward. Induction is the act or process by which an electric or magnetic effect is produced in an electrical conductor or magnetizable body when it is exposed to the influence or variation of a field of force. This means that moving electricity induces magnetism, and moving magnets induces electricity.
Our “train” is composed of a battery and two strong magnets whose fields are repelling each others. It’s track is a long solenoid, or tightly coiled copper wire. The battery sends a current through the solenoid, which creates a magnetic field. That induced magnetic field then interacts with the magnets, repelling one magnet (pushing it) and attracting the other (pulling it). This push from one end and pull from the other creates a net forward motion (or if it is the exact opposite, then it will bounce out of the track due to a net backward motion).
If the two magnets are aligned with the battery such that their fields are attracted to one another, then there will be a net of zero movement. This is due to the induced magnetic field pulling the magnets in opposing directions. But, don’t take my word for it, give it a try for yourself!
Oil and water won’t mix no matter how hard you try. They have different densities and different polarities. But what happens when you mix oil and milk?
Milk is an emulsion. It is made of mostly water with lipids throughout. Lipids are organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents.
Water is a “polar” molecule, meaning that there is an uneven distribution of electron density. Water has a partial negative charge (-) near the oxygen atom due the unshared pairs of electrons, and partial positive charges (+) near the hydrogen atoms. Due to the polarity, the attractive forces are very strong in water molecules. Oil is nonpolar, which means the attractive forces are pretty neutral.
Any liquid, to be able to mix with another needs to have nearly equal amounts of attractive forces among the molecules of both liquids. When you add oil to a bowl of milk something bizarre and amazing happens. You will see hundred of spheres form. The spheres are drops of milk which are surrounded by a layer of oil. These are technically bubbles!
But these bubbles are pretty hard to pop. You can even stir them and see how they move through the layer of oil! Give it a try for yourself.
Most stone is made over millions of years, cooked in the core of our planet. That stone then erodes over time due to wind, acids found in rain and groundwater, and other natural weatherings. Chalk is a type of limestone formed by the shells of microscopic marine organisms.
The process of erosion can produce beautiful features in earth’s crust, like arches, stacks, and caves. This process usually takes tens of thousands of years.
But we can make a limestone cave in just a matter of minutes. All you need for this DIY chalk cave is a block of chalk and vinegar.
The vinegar, a weak acid, reacts with the calcium compound, dissolving it. It then forms carbon dioxide gas, water, and an aqueous calcium solution. This same process takes place for real caves, but the acid in rain and ground water is much more diluted, therefore taking much much longer to see the results.
We’ve all experienced a mood ring change color when you put it on your finger. But have you ever seen slime do that? Thermochromism is the property of substances to change color due to a change in temperature. Here is a DIY to make your own thermochromic slime.
What you need:
¼ cup white glue
1 tablespoon water
3 teaspoons thermochromic pigment
¼ cup liquid starch
Mix all of the ingredients together and there you have it! (If it is very sticky, add more starch until it doesn’t stick anymore.) You just made your very own heat sensitive color changing slime. But how does it work?
There are two types of thermochromic materials. The first is liquid crystals. The temperature change causes a movement in the crystals which changes their spacing. The change in spacing causes light in the crystal to refract at different wavelengths than before. Refraction is the change in direction of propagation of any wave as a result of its traveling at different speeds at different points along the wave front.
The second type of thermochromic material is called a Leuco dye. A temperature change causes the dyes to change their molecular structures. A change in molecular structure will cause the dye to reflect different colored light. Reflection is the throwing back by a body or surface of light, heat, or sound without absorbing it.
Your thermochromic slime uses Leuco dyes to show the difference in temperature when you play with it. Can you think of anything else to use to manipulate it’s color? What happens when there is an extreme temperature change?
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