A self-teetering candle
In this trick, a candle balanced between two glasses is able to move without being touched, teetering back and forth like a seesaw. According to Isaac Newton's third law of motion, "for every action, there is an opposite and equal reaction." As wax drips off each end of the candle, the heavier mass shifts from one side to the other, causing the candle to rock back and forth.
A microwaveable plasma ball
In this trick, when you microwave a lit matchstick trapped in a glass, it erupts into a violent ball of plasma.
Here's how it works:
When something is on fire, electrons are freed from its atoms. But this freedom doesn't last very long — the electrons are usually recaptured by the molecules, causing them to lose energy and emit light, giving fire its signature glow.
But in a microwave, the electric field actually shoves the electrons above the source of the fire, shaking them around, and causing them to smack into air molecules. This kicks them into even higher-energy orbits. As the electrons fall back, they emit light, producing a glowing ball of plasma above the flame. Since the plasma is hotter than the air around it, it usually rises.
A ball moves in slow motion down a slope
It's actually possible to cause objects to move in slow motion down hills (without the help of special effects). To do this, you use a thick liquid, such as honey, a heavy metal ball, and an empty ball-shaped container. Place the heavy ball in the lower half of the sphere and fill the lower half of the container with honey.
The thickness of the honey hampers the speed at which the inner sphere spins around, causing the ball to move very, very slowly down the slope.
A puddle of water flows upward into a glass
This effect is produced when you place a burning candle on a plate covered in water and then cover the flame with a glass. As the flame starts to burn out, the water rushes upward into the glass kind of like... magic.
What's actually happening is the flame is raising the temperature of the gasses trapped in the glass, making them push outward against the liquid. As the flame fizzles out, the temperature of the gas falls back down. This lowers the pressure in the glass, causing the water to flow into it.