ingridscience

Fill the fish tank with water (do not try to move after filling).
Add a few drops of milk and swirl around. The milk will only just be visible. It is easy to add too much.
Darken the room.
Ask students to shine their lasers in the tank, observing what happens when it hits the glass at the sides of the tank, as well as the surface of the water.

The lasers will reflect off the glass, and also the surface of the water, which behave like mirrors. Also interesting is that some of the beam reflects back and some does not, so the path of the laser light is split, so with multiple reflections interesting patterns can be made from just one laser beam.

For more experimentation add mirrors under the water for students to move around.
https://www.youtube.com/watch?v=aN1saYRr6z4

Set up the pulley system as shown, first with just one pulley at table height - the rope passes from the weight and through the pulley only.
Feel the force that it takes to pull the weight up.

Then add a pulley to the water bottle. Pass the rope back and forth between the fixed pulley at the top and the moveable pulley at the bottom, so that four rope lengths are holding up the bottle.
Feel the force needed to lift the water bottle, and compare to the single pulley system previously done.

As more lengths of rope are pulling the weight up, the force needed to pull the rope is less. With four ropes pulling up the weight, the force required should be a fourth.
But in exchange, more rope will have to be pulled through (less force over a greater distance, compared to more force over less distance with just one pulley).

Assemble as pictured.
The rod holding the pen, must be able to freely move up and down, but with out any sideways wiggle. I had to hold with my hands to prevent losening.

Pin the paper to the board.
Add the cans in the corners for weight.
Set the board in motion.
Then drop the pen on the board.
Do not touch anything that will impede the free swinging of the board or the motion of the pen arm.

Construct the cannon:
Cut a hole on one side of the box (works best if this is about half the diameter of the box).
Cut part of the other side of the box out, and tape a plastic bag over it, so it is a little flexible.
Add a handle to the plastic with tape, so that it can be pulled back and forth.

Add the container of warm water and dry ice to the box.
Once the box fills with dry ice gas, draw back the plastic then move it forwards quickly.
A vortex of gas should emerge from the hole (best seen against a dark background).

Scaled down, individuals can each make their own vortex.

1. Place a nugget of dry ice in an empty aluminum pie pan and press on it with a metal spoon. You should hear squealing or squeaking sounds as the spoon and pan vibrates. This is caused by heat from the spoon and pan warming the carbon dioxide and changing it from solid to gas (sublimation), which then pushes the ice away from the spoon and pan, causing them to vibrate.

2. A nugget of dry ice vibrates on a spoon as it sublimates and the gas escapes under it. Once the dry ice has cooled the spoon down, the vibration stops, and water vapour in the air turns to ice crystals on the cool spoon.

3. Press side of coins into dry ice. The coins flip back and forth. The warm coins heat the dry ice and turn it to gas. The gas escapes in the enclosed space pushing the coin back and forth.

Push one end of the tubing through the base of the polystyrene cup.
If a funnel is available attach to the other end of the tubing, using tape if necessary to seal any gaps.

Add warm water and a (gloved) handful of dry ice pellet to the bottle, to start the bubbling.
Place the funnel over the bottle, so that dry ice is pushed along the tubing.

Once dry ice gas is coming out of the tubing at the end with the styrofoam cup, dip the rim of the cup into the container of detergent.
A large bubble should form with swirling dry ice inside.

The dry ice bubbles will fall quite rapidly, as carbon dioxide is heavier than air.
They are fun to have pop on your hand, when the dry ice cloud flows out of them.

As the dry ice bubbling in the bottle slows, replace the now cold water with more warm, and add more dry ice pellets if necessary

Use a pencil sharpener to make crayon shavings of different colours into the pie cases.
This represents sand and mud made up of different "minerals".
Fold several colours into greaseproof paper and hammer it flat. The minerals are pressed together into one piece of "sedimentary rock".
Place the pieces of sedimentary rock into a pie case, then heat with a hair dryer. As they start to melt together they represent "metamorphic rock", then as they flow together completely they are "magma" inside the earth. As they cool to form a mixture of minerals they are "igneous" rock.