ingridscience

If this activity is run inside:
Show or challenge students to reflect the beam of a flashlight off a mirror and onto a white board. It will be easiest for them if they lay the mirror on the floor or desk, and then shine the flashlight down onto it at an angle, to make the light reflect back up onto the board (which is in front of them). Older students may also be able to hold the mirror and the flashlight and arrange the angles to reflect the light onto the board.

If this activity is run outdoors on a sunny day:
Mirrors can be used bend the sun's rays around an object and bring light into its shadow. Students may be familiar with seeing sunlight reflected off objects forming bright patches. Show students how to use a mirror to make a splash of light in the centre of their own shadow.
Outside, they may find it easier to squat down to make a large shadow, then have the sun shine over their shoulder onto the mirror, which is tilted to reflect onto the ground in front of them. Younger students might need assistance with the placement of the mirror and themselves relative to the sun. A sheet of light paper makes the patterns more clearly seen on a rough or grey ground.

Show all students that by drawing on the mirror, or by making a shape out of a sticky note, they can make patterns and shapes within the patch of reflected light.
Challenge them to write their name or an image, so that it appears right-side-up inside the shadow.

Help all students visualize the path that the light rays take, to reinforce how they are making their patterns, and how shadows are formed.

Discuss some big ideas that students are discovering: Light goes in straight lines and can be reflected. Some surfaces reflect light, some do not.

This activity can be used to demonstrate the Moon's appearance: the light areas reflect the sun's light and look white (made up of anorthosite, a kind of feldspar (the plagioclase form)), while the dark areas (basalt lava flows) do not reflect light and look dark.

Collect flat plants, or other objects, to arrange. Spend time deciding on the design.
When ready with the design, take the sun print paper from its packaging and quickly move the arrangement onto it. If possible lay a piece of plexi over to make them very flat and to stop them from blowing away.
Wait until the paper turns from blue to almost white.
Take off the plants and immerse the paper in a tray of water. Wait until it turns back to blue, then remove from the water.
Dry the paper.

The sun exposes the parts of the paper that are not in the shadow of the plants.
The water fixes the design.

Allow students to experiment freely with making shadow shapes with their hands and the cloth.
If you are indoors, show students how to pin the cloth tightly around the frame with the clothes pegs then use the free hand to shine the flashlight beam through it onto the board. They will also enjoy making shapes by adding frames together. They will need to work with a partner to make hand shadows, with one student holding the flashlight.
Optional: give them a printed sheet of hand shadows. There are many online e.g. http://krokotak.com/wp-content/uploads/2015/01/79.pdf
Students may also experiment with the angle they hold the shape at, and how as it turns the shadow changes shape.

Ask them to notice, and record on a worksheet if you like, where the light comes from and how the shadows are made.
Give them a challenge: make the shadows taller or shorter.

Discuss as a group what they found and guide students in understanding the principals of light they are discovering:
If an object blocks light, it will make a shadow in the same shape as the object. Shadows are the lack of light. Light travels in a straight line. Some objects are thin enough to allow some light to pass through them.
If the object is near the light source the shadow will be large, if it is far the shadow will be small. This can be explained by following the straight line of the light from the source, past the edge of the object to the projection wall. The angle between the edges of the object is much larger when it is close to the light source, so will end up following the line outwards to make a large shadow.

Students may have discovered moire patterns. If not, show them how to make them: lay two pieces of sheer cloth with very small holes over each other. Shine the light through them, and if necessary, move the cloth a little, to see new patterns of swirly dark lines which shift and change as the cloth moves. The last photo is an attempt to show this.

Some cultures make hand shadows a high art. There are many on you tube e.g https://www.youtube.com/watch?v=VpC9HSYMwdY
Guess the hand shadow animal: https://www.youtube.com/watch?v=J-3fHDUmnf0

Find an open concrete area that shadows will not pass over during the course of the lesson, and that will not be disturbed by other students.
Set the stick upright in the bottle. (Alternatively use the shadow from a lamp post or sign post.)
Draw a line along the shadow of the stick (or around the end of the post) and mark the time on the drawing.

Every 30 mins (or down to 5 minutes with a longer lamp post), draw in the new position of the shadow and mark the time again.
Once they get a sense of how far it will move, students can be asked to start predicting where the shadow may fall after a certain amount of time. (No point in asking them to predict before they have some sense, as it will be wild guesses, making them feel successful or not for no reason.)

Observe how the shadow moves over time (it is surprisingly fast).

As the earth rotates the position of the sun in the sky changes, so the shadow rotates around the stick.
Hence the position of the shadow can tell us how much time has passed, therefore the time.
Over the next day or so, the time can be predicted from the position of the shadow.

The length of the shadow depends on how high the sun is in the sky and will change with the time of day and the seasons.

Note: this simple sundial with an upright stick will not work for telling the time over the course of the year. Precise sundials are at an angle, and have more complex readings for measuring time.

Add hot water to one container, and cold water to another. Allow to sit for 30 seconds so that the water is not sloshing in the container.
Drip one drop of yellow food dye at one side of each container, and one drop of blue food colouring to the other side of each. (Alternatively, just a drop of blue in each.)
Watch how the food colouring mixes through each.
The blue and yellow will mix much faster to make a green colour in the glass of hot water. (With blue alone it will mix into the warmer water faster.) This is because the hot water has currents in it (as water evaporates from the surface). The food dye molecules get carried along by these currents.
The colder water has slower currents, so the food dye does not mix into the water as quickly.

Note that this is not diffusion, but showing the water currents in hot and cold water.

Start with the N2 molecule.
Then give students the atoms needed to move around the cycle.
Give them clues each step to aid in model building: they might make two identical molecules, or that they should make a water molecule first, then use the remaining atoms to make the molecule with nitrogen in from the remaining atoms and bonds.

At each step, explain how living things make and use the molecules:
Plants need nitrogen but are not able to use the nitrogen in the air. They rely on bacteria to catch it.
Bacteria in the soil, and some specialized bacteria that live in the roots of some plants can “fix” the N2 to make NH3 (and also NH4), which can be taken up by plants.
In the soil extra ammonia is converted to another molecule, nitrate, by bacteria when there is oxygen around.
Nitrate is converted to nitrogen gas again, by bacteria. More H is used.

Walk to collect soil from various sites around the school/neighbouring park. Add collection sites to a map.
Take soil from 10cm below surface to make sure the chemistry of the actual soil is measured.

Mix 1 part soil with 5 parts water. We added 5ml soil to a tube, then water to 30ml. Shake 1min, then settle 10 mins (allow to settle on walk back).

In class, filter the soil, by carefully pouring the water that is above the settled sediment through a coffee filter paper into a new tube.
Some soil samples will now be clear, some will not. Run again until they are as clear as they can be (so that colour tests are easier to see).

pH test
The first chemical test of our soil samples is for pH, which measures how acid something is. Soil does not get extremely acid, or extremely basic in the other direction, but it will vary enough to affect what can live in it.

Our instructions for testing: Add pH powder from capsule. Add 4ml of the liquid to tube. Shake 1 min. Record pH.
See the map image for the soil pH readings we got from around a school and neighbouring park.

Discussion of pH results:
What might affect how acidic or alkaline soil is?
Rainfall: Acid soils are most often found in areas of high rainfall. Excess rainfall leaches base (the opposite of an acid) from the soil. Additionally, rainwater has a slightly acidic pH of 5.7 due to a reaction with carbon dioxide in the atmosphere that forms carbonic acid.
Weathering of minerals: rocks are broken up and washed into the soil, and affect its pH.
Plant root activity: plants release H+ ions from the root.
Acid rain: When atmospheric water reacts with sulfur and nitrogen compounds that result from industrial processes, the result can be the formation of sulfuric and nitric acid in rainwater. The amount of acidity that is deposited in rainwater is much less, on average, than that created through agricultural activities.
Fertilizer use: Ammonium (NH4+) fertilizers react in the soil in a process called nitrification to form nitrate (NO3−), and in the process release H+ ions.

Different plants are adapted for different amounts of acidity. Bogs are usually more acidic.
Potting soils are manufactured to be neutral so that a wider range of plants can grow in it.

NPK tests (nitrogen, phosphorus, potassium)
Instructions with our soil test kit: Add N/P/K test powder from capsule. Add 4ml soil liquid. Shake 1 min. Allow colour to develop - about 10 mins.

While the colour is developing, look at the chemistry of one of these in the environment: nitrogen - do the "molecular modelling of the nitrogen cycle" activity.

Look at our tests
Our nitrogen results (pink) were very low - what does that mean? Not much nitrates. The nitrogen might be in other forms: nitrite or sequestered in the plants and animals.
(One of the potting soil tubs had higher nitrogen).
Nitrogen is needed for proteins, and chlorophyll, which makes the leaves green.
If plants turn yellow, they may need fertilizer.

Phosphorus was very low in woods, higher in one potting soil. Phosphorus has a whole other cycle. Needed in plants for photosynthesis.
We need it to make ATP, which carries energy.
In whole grains and nuts.

Potassium was higher everywhere. Whole other cycle. Needed in plants for photosynthesis; proteins.
We need it for our nerves to fire.
In potatoes, tomatoes.

Many other minerals needed by plants.
We eat the plants and get them too.

Submerge an uncooked egg in vinegar, and place in a safe place on a counter or shelf.
Wait a few days to a week.
Look at periodically to follow the changes.

The shell will bubble as the vinegar reacts with the calcium carbonate in the shell, releasing carbon dioxide gas:
CaCO3 (calcium carbonate of the shell) + 2 CH3COOH (acetic acid of vinegar) -> Ca(CH3COO)2 + H2O (water) + CO2 (carbon dioxide gas)

The hard shell reacts away completely, leaving the egg surrounded just by the membranes. The egg is soft, but still intact.
The membranes prevent bacteria from reaching a developing chick inside the egg, and stop moisture from leaving too fast and allow air and other gases to pass.

Students build a wooden project.
We built a perch for chickens.
As the pieces of wood are cut and attached together, discuss how each tool is a simple machine, and how it makes the job possible.

Saw is a wedge.
Hammer is a lever.
Nails are wedges.
Screw is an inclined plane.
Screw driver is a wheel and axle.