ingridscience

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 on the lining of your nose, which sends a signal to your brain. Only when it reaches your brain is it interpreted as a smell.

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). Again 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.

For younger students, this works well as a group activity with students sitting in a circle. The teacher rubs the foam flat in their hair then drops the pie plate on it, so that one student can simply bring their finger close. The whole group will hear the static electricity as it jumps.
Then the pie plate can be lifted for the next student to bring their finger close.
Only charge again once the sparks cease (after about 4 goes), or a student accidentally touches the pie plate.

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, or with a dry hand.
The small objects will stick to the plastic sheet, and sometimes even dance up and down on their own.

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

To make classic slime.
Make 50% white glue in water. Give students 2 Tablespoons each in a cup.
Mix 1 tspn borax into 1 cup water. Give students 1 Tablespoon each in a cup.
Students mix the cups together and stir quickly until combined.
(For measuring everything individually, use recipe 2 below.)

Play with the slime: it can flow between the fingers, but when it is suddenly pulled it breaks.
Chemical explanation of how slime is made:
The glue contains long molecules (called polymers). When borax is added it makes permanent (covalent) bonds between the glue molecules, called cross-links. These cross links form a branching web of glue polymer molecules, giving the slime its thick texture.
The following activity compares two different kinds of slime/silly putty, with different amounts of cross linking.
Chemical explanation of how silly putty behaves:
There are other bonds between the slime molecules (called hydrogen bonds), which are weaker bonds and can easily break and reform. When the slime is pulled slowly, a few of the hydrogen molecules break, but then reform with another adjacent polymer. As these hydrogen bonds continually break and reform, the slime stays in one piece but can flow and change shape. However, when slime is pulled on suddenly, many hydrogen bonds are broken at once, so it breaks apart.

To make two different slime/silly putty recipes, with different consistencies
Ask students to work on the tray, as this activity is messy.

First make the classic slime recipe as follows:
Give students their materials: 4tspns of glue in a cup, an empty cup, a squeeze bottle of water and a tablespoon measure, borax powder in a cup and a 1/16tspn or equivalent measure (I use two scoops of a very small measure).
Instructions for students:
To an empty cup, add 1 Tbspn water and 1⁄16 tspn borax. Mix well.
To 4 tspns glue in a cup, add 1 Tbspn water. Mix well.
Pour the borax mixture into the white glue mixture. Mix well.
Lift the blob out of the cup, and into a small baggie.
Mould with hands through the bag to mix completely.
Pull the blob out of the bag, leaving any liquid behind.
Mould with hands until smooth.

Allow students time to play with their slime.
If slime is not stretch enough, gradually work in some more water.

Discuss how and draw how the borax molecules cross link (or bridge) the long glue molecules, binding them together so that the glue is more solid but can still flow.

Then make another slime recipe:
First tell students that they will add a lot more borax to this recipe and ask what more cross links of borax will do to the texture of the slime that they make [it will be more solid].
Do the experiment:
To an empty cup, students add 1 Tbspn water and ½ tspn borax. Mix well.
Pour the borax mixture into the cup of 4 tspns white glue. Mix well.
Lift the blob out of the cup, rest for 5 minutes.
Mould with hands into a ball.
Roll in cornstarch to make less sticky.

This recipe makes a much more solid ball, which can be bounced.

Review the consistencies in terms of the molecules that make silly putty (see last photo):
In a chemical reaction, the borax molecules bridge (or "cross-link") the glue molecules together, turning the two liquids into something more solid.

Other background chemistry: White glue is a polymer, which is a long chain of repeating units. Other polymers are nylon and plastics, as well as naturally occurring rubber. Polymers can be cross-linked at any of the repeating units along their chain, so the amount of cross-linking determines how solid they become.

Slime is a non-Newtonian fluid - its viscosity changes depending on how much force is applied. (Standard Newtonian fluids only change viscosity with changes in temperature.) When a sharp force is applied to slime it becomes rapidly more viscous and behaves more like a solid.
More info on slime: http://www.acs.org/content/dam/acsorg/education/resources/highschool/ch…