ingridscience

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.

Take a balloon and fluorescent bulb into the dark room.
Rub the balloon on your hair. This will transfer electrons from your hair onto the balloon and charge the balloon with a negative charge.
Bring the charged balloon near to the fluorescent bulb, and the bulb will light.
If it does not work right away, keep charging the balloon and trying again.

The static electricity of the balloon energizes the atoms or the mercury vapour inside the bulb. (The wall electricity does the same thing when you plug the bulb in.) As the mercury releases this energy again, it gives off UV light. This UV light collides with the phosphors in the bulb (seen as a white coating), and makes them glow. The glowing phosphors light up the bulb.
This works with a fluorescent bulb, because it needs less energy than an incandescent bulb to give out the same amount of light.

Rub the bottom of the styrofoam/foam block on your hair. (Electrons transfer from your hair to the styrofoam, giving the styrofoam a negative charge.)
Drop the styrofoam upside down on a table or on the floor, so the negatively-charged surface is now up.
Use the handle to pick up the pie tin, then drop it onto styrofoam - do not touch the pie tin or styrofoam. (Electrons in the pie tin move away from the negatively-charged surface of the styrofoam, and so cluster on the top side of the pie tin.)
Very slowly bring the tip of your finger towards the pie tin. You should feel a tiny spark when your finger is very close, but not touching. (Electrons jump from the pie tin to your finger, to get away from the negative charge of the excess styrofoam electrons.) This spark is static electricity. Lighting is also static electricity, but with much more energy.

The pie tin is now short of electrons. Use the handle to pick up the pie tin again (so this charge is not lost). very slowly touch the edge of the pie tin with the tip of your finger. You should feel another small spark. (The pie tin, short of electrons, attracts electrons from your finger which jump across).

Drop the pie tin onto the Styrofoam tray again, and repeat. You can do this over several times before the sparks cease.

Lightning is static electricity:
A lightning bolt is a dramatic example of static electricity.
In a thundercloud water droplets are caught in the updrafts and lifted to the top of the cloud where they freeze. Ice and hail move down in downdrafts. Ice and water bump together and electrons are transferred making positive and negative charges.
The strong negative charge in the bottom of the cloud attracts positive charges in the ground, which move up the tallest objects. A “leader” of negative charge descends from the cloud seeking out a path toward the ground. When it gets close to the ground, a positive charge “streamer” reaches up to meet the negative charge. When the channels connect electricity flows and we see the lightning stroke, which may repeat until the electrical discharge is complete.
The electric field often discharges between clouds.
(Thunder: lightning heats the air around it to high temperatures (30,000 °C). The heated air expands explosively, creating a shockwave as the surrounding air is rapidly compressed. The air then contracts rapidly as it cools. This creates an initial crack sound, followed by rumbles as the column of air continues to vibrate.)

Put a few of the small objects in the tray or petri dish.
Put the acrylic sheet over or put the lid on the petri dish.
Rub the top with the cloth.
The small objects will stick to the lid, and sometimes even dance up and down.

Allow students to free play and explore what objects dance and which don't.
They can take notes on what they find.

Maybe give them different cloths to try. Rubbing one's hand on the lid, instead of a cloth: works quite well when the hand is dry in an indoor dry environment.

Sometimes the effect will stop after a while - try turning over the plastic sheet.

Explanation:
When the cloth is rubbed on the plastic lid, electrons are transferred from one to the other (whether the cloth or the plastic lid takes the electrons depends on their relative positions in the "Triboelectric series"). The lid is now charged with a negative or positive charge. The small objects are attracted to this charge and so stick to the lid.