ingridscience

Hang the ruler/paint stick/popsicle stick over the edge of the desk.
Push it downwards, then let go, so that the ruler vibrates and makes a sound.

1. Change how much of the ruler is hanging over the edge of the desk and experiment with the different notes that are made. The "pitch" is how high or low the note is. A longer ruler hanging over the edge makes a lower pitch; a shorter ruler gives a higher pitch.
Note that the longest ruler may not make much of a note except the slapping against the desk, and the shortest ruler will not make a note at all, so work in the middle of the ruler. It also helps to start with a longer ruler, twang it, then make the ruler shorter while it is still vibrating. Then it is easier to hear the note rising in pitch as the ruler is moved.

2. Observe the vibrations of the ruler closely to correlate the frequency (speed) of the vibrations with the pitch of the note.
A longer ruler vibrates more slowly, so has a lower frequency. A shorter ruler vibrates more quickly so has a higher frequency.
Note that it is hard to see the vibrations as they get very fast when the ruler is very short, so start with the longer ruler and move it gradually slower.
This video shows the vibrations in slow motion: https://m.youtube.com/watch?v=4SpSwTvbZI4

Worksheet attached below for older students.

Discuss how the sound is made and why the pitch changes:
The vibrating ruler pushes the molecules in the air, making them bunch together. As the ruler vibrates back and forth it makes waves of molecules pushed together (pressure waves). The molecules transmit these pressure waves through the air into our ear, where they are converted to electrical signals that get sent to our brain.
When the ruler is longer it vibrates more slowly, so pushes molecules together less often, so the waves of molecules are further apart - the frequency of sound waves are lower. Lower frequency waves have a lower pitch.
When the ruler is shorter it vibrates more quickly, so makes higher frequency pressure waves, which have a higher pitch.

Making music with a ruler on a desk: https://www.youtube.com/watch?v=3qPzsoQzo9s

Add the water to the cornstarch - amounts don't matter as long as the ratio stays the same at twice as much cornstarch as water (by volume).
Add the water to the cornstarch, and as you approach the final amount, add water more slowly and mix well each time.
Stop adding water when it feels like a liquid while you're mixing it slowly, but can be scooped up like a solid if you move fast. It will not be powdery and feels hard when you tap on it. Should be close to 2:1 cornstarch:water.
Once you play with it for a while and some of the water evaporates away, a little more water may need to be added to get to the right consistency again.

Invite students to play around with the oobleck - it acts very strangely!
Pick up a handful and squeeze it. Stop squeezing and it will drip through your fingers.
Tap a spoon on it, then rest the spoon on the surface - it will slowly sink.
Rest your fingers on the surface of the oobleck. Let them sink down to the bottom of the bowl. Then try to pull them out fast. What happens?
Take a blob and roll it between your hands to make a ball. Then stop rolling. The oobleck will trickle away between your fingers.
Put a small plastic toy on the surface. Does it stay there or does it sink?

Oobleck is tiny particles of cornstarch distributed in water. Cornstarch is a chain of sugar molecules (a polymer) called amylopectin.
This kind of mixture, with tiny particles of one substance mixed into another, is called a colloid. In this case, solid particles are mixed into a liquid.
To separate this mixture, the water can be evaporated away to leave the cornstarch - this will happen quickly if the oobleck falls as drops on a desk or surface.

Water and other liquids have certain properties and behave like many familiar fluids - if you stir them they move out of the way quickly. Oobleck doesn't act like these - when oobleck is hit or moved suddenly, it gets more rigid, or viscous.
Something that behaves in this way and changes it's viscosity (thickness) is called a non-Newtonian fluid.

Why does ooblek behave in this way?
If moved slowly, the cornstarch particles have water between them which allows them to slide past each other. But if ooblek is moved quickly or hit, the water is squeezed out from between the particles and the friction between the cornstarch particles increases a lot, locking them together so they can't move past each other.

Ooblek slow motion video (including running on it): https://youtu.be/G1Op_1yG6lQ
More about oobleck from a research lab that studies it: https://www.youtube.com/watch?v=JGfynrsdaV0

Quicksand is also a non-Newtonian fluid, but it acts in the opposite way from ooblek, when hit or pressure is exerted on it, it becomes more fluid. If you ever find yourself sinking in a pool of quicksand, try swimming toward the shore very slowly. The slower you move, the thicker the quicksand will be and so you can push against it.

Inflate the balloon - do not tie it off.
Hold the balloon closed with a small binder clip.
Writing a message/name and draw on the balloon. Try fat and thin permanent markers.
Deflate the balloon.
Marvel at the beautiful tiny writing!

For a lesson on smell:
Add each of the ingredients to the bowl, smelling each one as they go in.
Spread the oat mixture on the tray.
Bake at 350 degrees for 15-20 mins.

During baking time, do another activity e.g. perfume making.

When the baking oat bars start to smell, ask students if they smell them.
Did they smell this smell in the original ingredients?
During baking, chemical reactions between the ingredients and the heat of the oven made new odour molecules. These smelly molecules bump through the air until they reach your nose.

Once the oat bars are starting to brown, remove from the oven and divide among the students.

Discuss with students that smell is a big part of what we call taste. Ask if they have noticed that when they have a cold (and their nose is stuffed up) that they can't smell so well, and that tastes also change.
Ask students to hold their nose when they take their first bite of oat bar. How does it taste?
Now ask them to release their nose and take more bites. Does the taste change when smell is added in? A lot of what we taste is actually smell.

For a lesson on sources of food for birds:
Add each ingredient to a bowl, while discussing where it comes from (which living thing makes it) and who would eat it.
Mix all ingredients together. Firmly press into a lightly greased baking dish (about 6X7 inches). Bake in a 350F oven fro 15 mins, or until golden.
Let cool and cut into squares and give a bar to each student.

Hide the orange behind the screen, so that students do not see it before the activity.

Start to peel the orange behind the screen and ask students to raise their hand when they can identify the smell that is floating their way.
Note that people's sense of smell differs widely, so some students will smell and recognize it quite quickly, and others may have trouble identifying it. Do not require that everyone smells the orange before revealing what it is.

Explain that smells are small molecules moving through the air. (The main molecule that makes orange smell is called limonene.)
It takes a while for the smell molecules to be carried on air currents away from the orange, hence the students nearer the orange will smell it first.
Once the odour molecule reaches your nose, they fit onto larger receptor molecules, which sends a signal to your brain.