ingridscience

We use water to turn wheels to make electricity (hydroelectricity), catch fish (fish wheel) or grind flour.

Pour water over a wheel to show how it turns.

Optionally lift an object from the floor to the table top, using the force of falling water on the water wheel.

Before the class, prepare discs from the pie plates for the students, as cut edges are sharp:
Carefully cut out the flat part of the pie plate and discard the sides.
Punch a hole exactly in the centre with a pencil and enlarge slightly.

Students make cuts from the edge of the pie pan 2/3 of the way to the centre, in four or six places (to start, try modifications later). Fold over the sides of each section to make a paddle wheel shape.

Wrap a small piece of foam around the wooden rod and tape it in place. Push the rod through the hole in the pie plate, enlarging the hole until the plate fits snugly on the foam around the rod. The plate should not turn easily at all without the rod (the axle) turning.

Tape U-shaped pieces of foam to the centre of each of the short sides of the tray.
Lay the wheel and axle over the foam supports on the tray. Test that it can turn without hitting the bottom of the tray. If necessary, fold over the outside edges of the pie plate.

If objects are to be lifted with the falling water, make sure one end of the rod protrudes over the edge of the tray more, then tape the string to this end of the rod. Cut the string off where it meets the floor, and tie on a small weight e.g. the scissors.

Pour water from the 2L bottle onto the wheel. The weight of the water hitting the paddle blades generates a force which makes the blades move and the wheel turn.
Once the water runs out, pour the tray of water back into the bottle (using the funnel) for reuse.

If a weight is being lifted, the turning wheel turns the rod, which winds the string and pulls up the weight.
Challenge student to control how they pour the water to make the weight raise slowly or faster.

In a traditional water mill, a water wheel turns grindstones to make flour:
https://www.youtube.com/watch?v=1L5Pt4BLeos

A fish wheel turns in the moving water of a river and has attached netting to catch salmon:
Image here: https://gallery.janeandjohn.org/index.php/haines/FishWheel and in here: https://salmonlife.org/archived/stories/copper-river/
https://www.youtube.com/watch?v=-l81d3R1-OY
https://www.youtube.com/watch?v=uPoKHOMlhZ0
Fish wheels are used to catch salmon during a run, either for food or for tagging (to track salmon populations).

Hydroelectric power is made from a water wheel (called a turbine):
image: https://www.energy.gov/sites/default/files/styles/full_article_width/pu…
Video: https://www.youtube.com/watch?v=OC8Lbyeyh-E

Crumple the paper into a ball.
Place it in the mouth of the bottle.
Blow into the mouth of the bottle.
What happens?

The paper will usually shoot out of the bottle towards you!
If it does not, check that the paper ball does not take up more than half of the diameter of the bottle opening.

Why?
When you blow into the bottle, you add air to it, which increases the pressure inside.
The higher pressure air in the bottle will move towards the lower pressure air outside the bottle.
In flowing out of the bottle it pushes the paper out.

Please note that in a class of students it is likely that one of them is at least partially colourblind (1 in 12 males are colourblind). As this is an activity distinguishing colours, these students will not be able to tell some colours apart and perceive some colours differently, although the activity will be no less interesting for them. The common red/green colour blindness means reds and greens (or colours containing reds and greens such as browns) look similar. More information at colourblindawareness.org and colorblindguide.com/post/the-advantage-of-being-colorblind.

Turn out the room lights.
View the cloth under different light colours and see how the cloth colours change.
Colours will look their normal colour, a different colour or even black.

The colours appear in the cloth because of the colours (wavelengths) of light they reflect.
If white light hits them (as we usually have with the sun or room lights), the cloth will absorb parts of the white colour spectrum and reflect others - the reflected colours are the ones that we see.
However if only part of the white light spectrum hits the cloth, it is only able to reflect that part of the spectrum. If the cloth is white it will reflect all the colours hitting it, so will look the same as the light colour. If the cloth is another colour, it will still absorb some of the wavelengths, reflect some, and maybe appear a different colour.
For example, a red piece of cloth will reflect red light and absorb all other colours. So if a red light hits it it will appear red, but if a blue light hits it it will appear dark because it absorbs the blue light and reflects no light.
In the photos above, the colours that are fuchsia-coloured in white light (first photo) appear blue in blue light (second photo) and brown in green light (third photo). The pink reflects mostly reds and blues. With blue light hitting it, it can only reflect blue so appears blue. With green light hitting it (a mixture of yellow and cyan), it does not reflect many wavelengths, so appears a darker. Check the last light colour mixing image to see how light colours mix.

Explain that the ball is a model of the earth. Check that students know where the equator, poles, and their own city are.
Turn the room lights off.
Hold the flashlight level with the centre of the ball, from a couple of metres, so that a circle of light falls on the equator. Ask a student to draw around the circle. This models the sun's rays reaching the equator.
Keep the flashlight at the same distance but move it up so that it now shines on a more northern region of the "earth". Ask a student to draw around the patch of light on the ball now - it should be an elipse. This is how the light falls on the more northern regions.
Turn the room lights on and compare the outlines of the light patches. Discuss the intensity of light in each of the regions - it must be more intense at the equator as it covers a smaller area.

Explain that in the same way, the equator of the earth receives much more intense sunlight than the more northern and southern latitudes.

Relating to how weather starts, the tropics are warmed up more by the sun, and the warmer land and ocean there means the air above it is heated up more.

The sun's angle on Earth helps determine why we get different biomes;
Biome map: https://askabiologist.asu.edu/sites/default/files/resources/articles/bi… (from this article - https://askabiologist.asu.edu/explore/biomes) or https://cdn.britannica.com/38/102938-050-6B5388D9/distribution-biomes.j… for terrestrial (Earth, not water) biomes.

Note: pour water into the tubs a little ahead of time so that they reach room temperature (and start at the same temperature as the sand).

Add sand to one tub and water to another and place side by side in the plastic box. Add the thermometers so that they are submerged in the material, and read the temperature.
Lay the light over the box so that it is equally far from the tubs of sand and water. Leave for at least 5 mins, then take the temperature again. Take additional measurements over 20 minutes or more.
Graph the results.

For younger students plot the temperature reading at each time point.
Older students could alternatively calculate and plot rise in the sand and water, then add each as a single point to the graph. Data cleaner this way, but need to understand a rise in temperature.

The sand heats up much more quickly than the water.
In the same way, then sun heats up the earth's land (especially deserts) more quickly than its oceans, which means that living things in each environment have different adaptations suited to each environment.

This difference in heating between land and water also means that the air above the land heats up more than the air above the water, creating temperature differences therefore air movements.

Mix 4 teaspoons icing sugar with1 teaspoon baking soda.
Make a pile of sand on a heat-proof surface, and make a dent in the middle of it.
Pour fuel into the dent, then add some sugar/baking soda mixture.
Light it.

Long black "snakes" of carbon are extruded, made up of carbon and carbonate, puffed up with carbon dioxide gas. They crumble when they are touched (and make your hands black).
The reaction smells like marshmallows over a fire.

The chemistry:
C12H22O11 (sucrose sugar) + 12O2 → 12CO2 + 11H2O (g). This is complete combustion of the sugar in oxygen, which produces heat which makes the reaction continue. The water vapour escapes.
There are also some reaction products that are not made with oxygen (which happen in the centre of the pile):
C12H22O11 (sucrose sugar) → 12 C (black of the snake) + 11 H2O (gas).
2 NaHCO3 (baking soda) → Na2CO3 (carbonate that is also part of the snake) + H2O (gas) + CO2 (gas, which puffs up the snake)