ingridscience

Beat the egg whites until they start to get a bit thicker. Then add the sugar in two parts, beating between. Add the cream of tartar to help stabilize the foam. Add flavouring if desired. Continue beating until the mixture forms stiff peaks.
Note how the whisk beats air into the mixture, and that the air bubbles stay around as a foam.
Optional: carefully fold in food colouring to make swirly patterns.
Blob onto the tray and put in the preheated oven.
Cook until dry but not brown, about 1 hour. (With this cooking time it will be a little bit chewy in the centre. Yum!)
Allow to cool in the oven.

While they are cooking, do the foam molecule test to find out which components make the foamy texture - is it the protein of the egg whites or the sugar? Shake each in a small tube to find out. [protein in egg white makes foam, sugar does not]

Explanation: The foam texture of meringues is made by the protein of the egg whites, which surrounds the bubbles of air and stabilizes them. The protein molecules have different parts, some which like water ("hydrophilic") and some which do not ("hydrophobic"). The hydrophobic parts stick into the air bubbles (so only touch air) and the hydrophilic parts project into the water surrounding the bubbles. The protein molecules surrounding each air bubble stabilizes them so that they remain suspended in the mixture. When the meringue is baked the foam is hardened, to make a crunchy, airy dessert

This activity adapted from UC Boulder's Teach Engineering website.
This activity can easily expand to an hour lesson, and even longer with discussion at each group's tracks.

Students can build in pairs or in a larger group, up to four students is best.
It is helpful to have more than one building a run, so that one can hold the track in position while the other tapes.
The Play-Debref-Replay method of science teaching works great for this activity (see the resource).

Concepts covered can either be Energy transformations for older grades (potential, kinetic also sound, heat), or Forces on the marble for upper Primaries (gravity, friction), or Pushes and Pulls for lower Primaries.

Free experimentation activity:
The challenge: build a roller coaster for marbles. Discuss with students elements of a real roller coaster they have seen (loop, inclined loop, hill, corkscrew, banked curve... https://en.wikipedia.org/wiki/Roller_coaster_elements). Ask them to include two of these elements in the track they build for a marble.
Give each group 3 pieces of foam to build their track. Give them a cup to tape to end of their track so that the marble does not roll away.
Start Play. Students freely experiment to build tracks, encouraged to test it out continually as it extends if they are tending to build a huge track before running marbles down it. They will quickly learn what works and what does not.

Some tips for students, once they have been experimenting for a while, and if frustration creeps in:
Start as high as you can.
Make a loop smaller if the marble does not have enough energy to make it around a larger one.
Banking a corner (tipping up one side) might help keep a marble on track.

Debrief:
If time allows, gather the class around each track in turn to show their run, show cool features of their track, and explain how they overcame challenges, and if there is a feature they would like input on.
During this time, introduce some basic concepts and terms as age appropriate. For younger students stick with the forces on the marble - gravity pulls it down the track and friction slows it down. For older students discuss energy forms and transformation:
Potential energy ("gravitational energy", or "height energy" for younger students) is the energy the marble has from being high (most students intuitively start their track high, giving the marble a lot of potential energy to start it of).
Kinetic energy ("motion energy") is energy the marble has as it moves. It needs a lot of kinetic energy (i.e. must be going fast) to make it through a loop, or around a corner.
Energy is conserved as the marble moves, but is transformed between different kinds of energy. Starting high and stationary it has all gravitational potential energy, which is converted to kinetic energy as it rolls downwards. As a marble moves along a track its energy changes from potential to kinetic and back as it goes lower and higher. At the top of a hill it has a lot of potential energy, which changes to kinetic energy as it speeds up down the hill (and the PE drops). As it moves up a hill, it slows so loses KE, but gains PE as it gains height. Energy is conserved throughout.
The marble gradually loses all of its energy to friction with the track (rubbing against the track).
Friction generates thermal (heat) energy and sound, so when the marble comes to a stop all its initial potential energy has been converted to thermal and sound energy.
In a loop, if the marble is going fast enough, it will stay on the track. The marble wants to keep going in a straight line, so pushes against the track. The track keeps curving over, pushing back against it. A marble in a tighter loop will accelerate more than a marble in a wider loop. If the marble is not going fast enough, it will not push against the track enough and fall off.

Replay:
Return students to their own tracks, encouraging them to use other groups' ideas and incorporate into their own - engineers and scientists use each other's ideas all the time, and cooperate to make the best projects this way.
While circulating, insert the terms discussed during Debrief into conversations

Measuring and Graphing:
Students can measure the height of their tracks at various places and graph against a linear drawing of their roller coaster (see attachment for worksheet and photo). The height data correlates with the potential energy. Students can also indicate where the marble has most kinetic energy (where it is also losing the most PE).

Background information on real roller coasters:
A real roller coaster has no engine and once elevated to its start point is entirely driven by the force of gravity. At the start of the ride, which must be the highest point, the roller coaster has a certain amount of potential energy, and will not gain any more energy, but transfers PE to KE and back again, while losing both to friction.

Weightlessness and heaviness that you feel in a roller coaster car is from the combination of gravity and acceleration when the roller coaster changes direction.
More than 1g at the bottom of a hill (gravity gives 1g + acceleration down gives additional gs) - feels like you are being pushed down into the seat.
Less than zero gs at the top of a hill (negative gs from deceleration are greater than the 1g force of gravity) - feels as if you are being lifted up. Weightlessness can also be explained in this way: when the roller coaster car starts descent from the top of a hill, the riders and seat are both falling due to gravity, and without the force of seat pressing on them, the riders feel like they are weightless.

One ramp to vary height and object rolled down (younger students)
Each group of students sets up two ramps of different heights, and rolls a marble down each. As them to compare the speeds of the marbles i.e. which marble goes faster and ‘wins’. Students can measure the height that the marble starts at, to practice measuring. (Note that the ramps have to have quite different heights for the speeds to be noticeably different e.g. 20cm and 70cm).
Discuss why the marbles goes faster down the higher ramp. At the beginning of the ramp the marble starts with ‘height energy’ (called ‘potential energy’). With a higher ramp the marble has more height energy to start. The height energy of the marble changes into motion energy as it moves down the ramp. So a marble that starts with more height energy gets more motion energy so moves faster and goes further.
Ask students to compare rolling a pebble and a marble down their ramp. Make sure the tracks are the same height and the marble and rock are about the same size (so the only variable is the item being rolled down the track). A rock with a bumpy shape will rub against the track more - it has more friction. Friction is a force which slows things down. The marble can roll so it has little friction, so retains more motion energy and can go faster. Discuss other things that roll (anything spherical, wheels).

Kindergarten activity
Students work in pairs with two tracks only. Help them to tape the tracks together so that there are no tape bumps at the join.
If they want to include a loop help them to tape it together, although many Ks are happy with the hills and ramps that they create.
Discussion on why the marble rolls down the track: it is pulled down by gravity. Draw a hypothetical track on the board with an elevated end-point and discuss where the marble will eventually stop (at the lowest point).

U-track for marble collisions and energy transfer
Curve one track into a U shape and tape ends to two chairs. Use four marbles of different colours to roll down the track and try different starting positions to see how energy transfers between the marbles. (If the marbles are the same colour, students think that one marble goes through another rather than passing the energy to each other.) Marble collisions worksheet attached below.

Make sausages out of the modelling clay, and secure them to the tray to make the walls of a track across the tray.
Add water to the tray to fill the track, but not go over the tops of the walls.

Cut out a flat boat from the cardboard. Cut a notch in the back of it.
Place the boat at the beginning of the track.

Dip the toothpick in detergent, then touch the water in the notch of the boat.
It will move along the track.
The boat will move maybe once more before the tray needs to be emptied and refilled with detergent-free water.

Why does the boat move?
The surface tension is lowered in the area where the surfactant is added, and the higher surface tension in front of the boat pulls the boat forward. As the detergent spreads through the water, it decreases the surface tension throughout the water, and the boat stops moving eventually because there is no longer a difference in the surface tension.

By carefully lowering a paperclip onto the surface of the water, it will float.
If you are having trouble, use another bent paper clip to lower it onto the water surface. Remove the bent paperclip from underneath once the other one is floating.

How many paperclips can you float at once?
They will tend to attract each other.

Dip the toothpick in the detergent, then dip it in the water next to a paperclip.
The surface tension will be disrupted and the paperclip will sink.

At the surface of water, the water molecules attract each other relatively strongly so are pulled inwards.
This gives water droplets their round shape, as well as making the surface of water behave as if it has an elastic skin.
Light things are held up by this skin, such as water striders, and paperclips.

Detergent molecules interact with the water molecules and reduce the surface tension of the water.
Hence the surface of the water is no longer able to hold up light objects.

Open the soda.
Add a few raisins (or pour soda into a cylinder or tall jar, then add the raisins).
Watch them rise and fall.

The soda water is water with carbon dioxide gas dissolved in it.
The carbon dioxide in the soda comes out of solution and attaches to the raisins.
This decreases their overall density, so they float to the surface.
At the surface, the bubbles pop, the raisin becomes more dense than the liquid again, and sinks.
The cycle repeats.

The activity can be extended:
1. Ask students to cap their bottle and watch. The raisins will slowly stop dancing (as long as there is not too much air space at the top). The gas pressure in the air space at the top of the bottle prevents as much carbon dioxide gas from coming out of solution. When the cap is released the raisins will start dancing again as the pressure is released and gas is able to come out of solution once more, and sticks to the raisins. This capping and uncapping cycle can be repeated.
2. Ask students to shake their bottle, then slowly release the cap to expel the released gas. With less (or no) gas in solution, the raisins will not dance as fast (or at all).

Fill the bottle with water, to the brim.
Fill the eye dropper half full with water, until it just floats in the top of the bottle.
Top up the bottle with water and cap.

Squeeze the bottle to make the pipette sink.
Release to make it float again.

When the bottle is squeezed, air is compressed in the dropper as water enters it. This makes it more dense, so it no longer floats in the water.
When the bottle is released, the water leaves the pipette again, the pipette contains more air again. The air is therefore less dense again, so the pipette floats.

Human divers use weights to increase their density when diving.
Lifejackets decrease density, to enable a person to float better.
Submarines use tanks of compressed air to control their buoyancy. When ballast tanks are filled with water, the submarine sinks. When the ballast tanks are filled with air from the tanks, the submarine's overall density is decreased so it rises.

This activity is messy, and best done in a tray. Probably not suitable for a whole class, but for breakout groups with an attending adult.

Add a puddle of oil to one glass plate, spread out a little, then sprinkle iron filings on it.
Slowly lower the second glass plate, to avoid air bubbles. Add more oil from the edges with a pipette if necessary.
Move the top glass plate in a circular motion over the lower glass plate, to spread out the iron filings.
Use a magnet over the top glass plate to draw patterns in the iron filings.
Once a design is completed, slide a coloured piece of paper below the lower glass plate, being careful not to get oil on it, then photograph.

Remove the insulation from the last couple of cm of the magnet wire, at both ends, with the sandpaper.
Wrap the magnet wire around and around the pen, to make a coil. Leave 4cm at each end free. Remove from the pen and twist the ends together a few times to secure the coil. The uncoated ends should not be touching.
Tape the coil to the bottom of the cup, with the coil lying flat.
With the headphones removed from the headphone jack, strip the insulation off to reveal the bare wires underneath. Twist any strands of wire together to hold them together. Twist each headphone wire around each of the magnet wire ends, then wrap each in foil to make a good connection.

Start the music on the music player, plug in the headphone jack and turn up the volume.
Hold the cup against your ear with one hand, and hold the magnet against the coil with the other.
You should hear the music, maybe quite quietly. A stronger magnet, or multiple magnets, will make it louder.

The electrical signal through the coil from the music player, turns the coil into an electromagnet. The magnetic field changes with the changing electric signal of the music.
When the magnet is placed against the coil, it alternately attracts and repels the changing electromagnet's field, so pushing then pulling the coil away from it. This pushes the bottom of the cup in and out, which in turn, pushes the air near it back and forth. This is a sound wave is magnified by the cup, so that we can hear it.