ingridscience

Clear a classroom space, or move outside, to run this activity.
It can be run alongside other activities (see lesson plans) so that only a few students are running this activity at one time.

Ask students to choose a pole, and balance it on their fingers. They should do a few trials and count evenly, to see how long they can balance it, on average.
Give each student a lump of play dough.
Ask them to attach the play dough to the pole so that they can balance the pole for longer (several trials also needed). (Younger students can be shown how to push the play dough ball on to the top of the pole; older students can simply be given the play dough and asked to attach it as they wish.)

Once they get a sense of how the play dough makes a difference to how long the pole can be balanced, they can try different pole lengths/different sizes of play dough balls/different positioning of the play dough on the pole.
Give students some time to experiment, exchange ideas and to start formulating their own ideas to test.

Then ask students to think about the forces involved in keeping the pole upright.
Why do they think the play dough at the end of the pole allows them to balance it longer? (The explanation is complex, but encourage students to think about, and test out, their ideas around the forces involved.)

Gather as a group to discuss the students' discoveries and ideas, including discussions of their ideas about the forces involved.
No answers are wrong if they are reporting what they observed.

Explain how it works (though not necessary, especially if there is plenty of inquiry going on already which might be halted):
When the pole has no play dough attached, the top end of it tips over quite fast. Our hand has trouble moving fast enough to adjust to this to right the pole again, so the pole falls over quite rapidly. With the play dough at the top of the pole, the pole tips over more slowly and gives you more time to adjust your hand underneath it, so you can hold the pole upright for longer.
The top of the pole moves more slowly with the play dough mass attached because with the extra mass more energy is needed to move the top of the pole. With no mass added, less energy is required to move the end of the pole and so it moves faster. (Try flapping a pole back and forth with weight at the end - much harder than with no weight).
(Explanation in more advanced terms: the further the mass is from the pivot point, the more energy it requires.)

If the above explanation is discussed with students, they might want to experiment further with moving the mass to different positions along the pole and comparing how easily the pole tips over (or how easy it is to flap the pole back and forth).

For the balloon on the line:
Blow up the balloon and either hold it closed, or clip it with the binder clip to stop air escaping.
Attach the balloon to the straw with tape.
Release the balloon go.

For a simple activity, but one that is hard to control variables, the balloon can just be released into the air.

The force of the air rushing out pushes back on the balloon, making it move. (Newton’s 3rd Law: for every action there is an equal and opposite reaction).

Variables to explore:
1. Ask students to blow the balloon up to different amounts, and compare how far it goes each time.
2. Try adding mass, for example by adding pennies to a pot that is attached to the straw. If students are old enough to blow the balloon up to a consistent diameter/length, the results can be graphed for a visualization of this inverse relationship. For younger students the data is quite messy, I think because the balloons are not consistently blown up, and from other variables, so discussion can be around which number of pennies the balloon went the furthest (generally low numbers of pennies) and the balloon went the least far (generally high numbers of pennies).

The same principal is used to make rockets go into space. Rocket fuel is burned to produce a gas (see molecular modelling of real rockets). The gas produced builds up to enormous pressures and is released out of a small hole called a nozzle (like in your balloon). The gas rushing out of the nozzle from the back of the rocket, pushes the rocket upwards.
For discussion around the added mass, fuel is a significant mass in the weight of a rocket, so makes a large difference in how fast the rocket can be moved. The amount of fuel needed is calculated very precisely to eliminate any extra mass.

Show students how to put the balloon into the hairdryer airstream.

Leave them to experiment, with some prompting questions:
How far can you tip the dryer over without losing the balloon?
Can you throw the balloon and catch it in the airstream?
If you gently push the balloon out of the airstream, can you feel the force of the balloon being pulled back in?
How does this work?

Gather as a group and hear what students found, allow them to compare results. Ask for their ideas on why the balloon stays within the airstream. Encourage students to discuss in terms of the forces involved.

If the students are involved in their own ideas and discussions of what is going on, an explanation may not be needed, and may even stop their questioning and hypothesizing.
Only if students need an explanation, can this one be given:
The balloon stays at a certain height above the hairdryer when the force of gravity (which pulls the balloon down) is equal to the force of the air underneath the balloon (which is pushing the balloon up).
While the balloon is in the airstream, air curves around the base of the balloon then moves outwards and upwards, then over the top. As it moves outwards, all around the balloon, it pushes back on the balloon, holding it in the airstream. (Newton's Third Law of action and reaction.) You can feel this same force when you stick your hand out of a car window. When you tip your hand so that the air is directed down or up, you feel your hand being pushed up or down by the redirected air.
The balloon is kept in the airstream, even when the airstream is not vertical. If the airstream is tipped enough to one side, the effects of gravity overcome the other forces and the balloon falls.

In addition some explanations include the Bernoulli effect: the air that moves around the balloon is faster moving than the surrounding still air, so has lower pressure. The balloon is pushed by the higher pressure still air into the lower pressure air within the airstream.

You will collect DNA from your cheek cells.
You could get it from almost any cell in your body, as almost all your cells contain DNA.
There is even DNA in the root of a hair, or in cells left with a fingerprint, which can be collected for forensic investigations.
Cheek cells are the safest and easiest place to get it.

Collect cheek cells
1. Swish 5ml of water in your mouth for about 30 seconds, then spit it back into a cup.
2. Pour this mouthwash into a 50ml tube containing 1ml of 6% salt solution.
The swishing washes cells from the inside of your cheeks into the water. More vigorous swishing washes more cells off and yields more DNA. You collect hundreds of thousands of cheek cells in one mouth wash.
You are also washing bacterial cells from the inside of the mouth, so will isolate their DNA as well.
The salt solution is needed for the precipitation step later.

Break open the cells
3. Pour or pump 1ml of SDS solution to the mouthwash and salt solution.
4. Cap the tube, and mix the contents by gently inverting several times.
The detergent removes the greasy cell membranes from around the cheek cells (and bacterial cells).
The cheek cells also have a membrane around the nucleus, which is also removed.
The cell molecules (including the DNA) are released into the salt solution.

Collect the DNA.
5. Remove the cap. Rest a bent funnel in the tube (see image)
6. Pour 5ml of 95% ethanol into the funnel. The ethanol will run down the side of the tube, and makes a layer over the cell molecule/salt solution.
7. Hold the tube still for 30 seconds.
8. Look for the cloud of white, cottony strands of DNA forming in the lower half of the ethanol layer. There will probably be bubbles stuck among the strands, so if you do not see any DNA, first look for the bubbles. After a couple of minutes the DNA clump may float to the top of the ethanol layer.
Students can use a magnifier to look for the DNA forming - it gives a focus during the wait.
DNA is not soluble in ethanol, so it precipitates where the ethanol layer meets the cell molecule/salt solution layer. The salt from step 2 aids in precipitating the DNA. Most other cell molecules remain in solution.
The bubbles form as dissolved gas in the cell molecule/salt solution is forced out of solution by the ethanol.
Single DNA molecules are way too small to see - a strand seen here is a clump of thousands of DNA molecules.

Steps 9-12 should be done by the teacher or in small groups with close assistance
9. Locate the DNA in the tube. Hold the tube up close to your face, and move near to a light, so you can see
the DNA well.
10. Lower an acrylic stick into the tube, pushing it through the DNA clump, until it rests on the bottom of the tube.
11. Keep the stick resting on the bottom of the tube, and roll it between your fingers so that it spins in one direction. Do not spin it in both directions. Do not stir the stick in the tube, like you would stir a drink.
Keep spinning the stick in one direction until the DNA has wrapped around it.
If the DNA does not catch right away, repeat from step 10 with a new stick. The white DNA strands should
be visible on the black acrylic stick. They will look like a white goop.
12. Shake the DNA off into a small tube filled with 95% ethanol, scraping the stick on the side of the tube
if necessary.
If the DNA will not catch on the stick, use a pipette or eye dropper to suck it up. Avoid sucking up any of the salt layer, as the DNA will go back into solution.
Do not reuse sticks. They will not grab into the DNA again.
Different people get different amounts of DNA because some peoples’ cheek cells fall off more easily than others. If you get no DNA, make sure you swish really well when you try again.

Hang your DNA on a necklace
13. Thread the DNA tube onto a necklace string and tie securely. Students might instead make bracelets or a backpack memento.

The DNA should keep indefinitely in the small tube of ethanol. If the level of ethanol falls, top it up with some more.
The DNA you get is not pure DNA - there is also some protein mixed in. The long strands you see are clumps of DNA molecules. The protein is stuck to these strands and makes them a little whiter (and more bulky) than pure DNA.

More information

All living things contain DNA. You can adapt the above protocol to collect DNA from an onion, kiwi, or other fruit and vegetables:
Chop up the fruit or vegetable roughly. Drop it in a blender and add a cup of 6% salt solution. Blend for about 10 seconds. Drape several layers of cheesecloth over a cup. Pour the blended mixture onto the cheesecloth. Take a teaspoon of the liquid the drips through (which contains fruit/vegetable cells), and start at step 2.
You should get a lot more DNA than from your cheek cells, because you are starting with so many more fruit/vegetable cells.
For some fruits/veg it will be very hard to catch the DNA with a stick.

Model 1:
With a pair of scissors, push a hole through the centre of the card, or students can do it.
Cut from each corner towards the central hole, about 2/3 way in (leave a central area that is uncut to give it stability) - see photo.
Fold each corner upwards along the cut line (see photo), folding each segment in the same direction around the central hole.
Push a tube or pen cap through the central hole, then place on a skewer.
Blow from above to make the pinwheel turn. It may also turn from the side if the blades are angled appropriately.

Model 2:
Cut the windmill template (see attachment below) along the lines.
Twist the end of the wire into a loop, and add a bead against the loop (best done ahead of time with pliers).
Fold one corner of the paper template into the centre, push the wire through the hole at the corner, then fold over the next corner and push the pin through the hole on this corner. Continue with the last two corners, then add a bead to the wire before pushing the pin through the central dot.
Finally add two more beads (they keep the windmill spaced away from the pencil), and then push the wire through the base of the pencil erasor.
Wind the wire around the pencil, and cover with duct tape to secure.

Discuss in terms of force: our breath exerts a force on the pinwheel blades that make them move.
Discuss in terms of energy transfer: our breath is motion energy that it converted to the motion energy of the turning pinwheel.

Introduce students to the concept of force, if it hasn't been done already: a force is a push or a pull.
Hand out a ball of playdough each (about the size of a golf ball). Show students how to make it into a sausage.
Ask students to bend/twist/manipulate their sausage into a new shape, or simply move it along the desk. They should think of where their fingers apply force to make the new shape/move the play dough to a new position. Ask students to draw the new shape/position, and add arrows to their drawing where forces were applied.
Optional: introduce names for the things that forces can do to an object (push/pull/twist/bend/stretch/tear).
Gather group to show shapes and describe the forces used to make them.