ingridscience

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.

Just before the class, make a solution of 1:1 epsom salts:boiling water in a heat proof jar (using half a cup of each per table group). It will take a little while to dissolve all the crystals - heat in a microwave and shake alternately to make a clear solution.

Show the students how you make an epsom salt solution. Add a teaspoon of epsom salt crysals ito a jar of just-boiled water, and swirl until they dissolve. The salts seem to disappear, but the molecules of the epsom salts are in fact mixing completely in with the water molecules, to form a solution. Salt or sugar in water does the same thing.
Tell students they will be making a painting with a solution of epsom salts, but their solution is more concentrated (more epsom salts).

Distribute 1:1 epsom salt solution to shallow tubs on each table and give each student a piece of smooth black paper, a paintbrush and a flashlight.
Ask students to paint the epsom salt solution onto the paper, in any design they like. Emphasize to students that to get the best effect, do not repaint over a wet area, and make some deep puddles of solution. After a while, hand out flashlights for students to see better any changes on their paper.
Allow students to discover the formation of sparkly crystals, before discussion on what is happening.
As the water evaporates from the solution, the epsom salts will be left behind, and will organize themselves into crystals. Small crystals will form rapidly where the epsom salt solution is thin and water evaporates from it fast. In the deeper puddles, the water takes longer to evaporate and longer, spiky crystals have more time to form. Emphasize to students that to make the largest crystals, do not repaint over a wet area, as this will disrupt crystal formation that has already started.
Show students how the flashlights can be used to watch the crystallization process: shine a flashlight sideways onto the paper to see the sparkly crystals, and even see some of them growing as the water evaporates at the edge of a puddle.

Epsom salt crystals can also be seen growing on a knife, after dipping it in the epsom salt solution.

Students can fill out a worksheet to summarize and reinforce what the molecules are doing during dissolving and crystallization (see attachment).

Students can act out what the molecules are doing as the crystals form: some of them are water molecules and leave the group, while the others line up to form the remaining epsom salt crystals. Best in groups of 6.

If discussing crystal shapes:
The epsom salt crystal shape is technically a monoclinic prism - long with a lopsided, pointy tip. Whatever size the crystals are they will be this shape, but it is only really visible in the larger crystals grown in class or found in purchased epsom salts.

To make coloured crystals:
Mix watercolour paints with the epsom salt solution then layer thickly onto heavy white paper (e.g. watercolour paper). Overlapping colours will make nice effects.
It will take some time to dry, but is worth the wait.

Jar of epsom salts:
Epsom salts can also be grown in a cup or jar - simply dissolve the epsom salts in the water, and leave in an undisturbed place. A 3-D mass of crystals will form quite quickly. If there are no crystals once the liquid has cooled, tap the jar on a surface to initialize crystallization, and crystals will form very quickly - good to observe. Occasionally, crystal growth will be so slow that one or two giant crystals form.

NOTE: borax is toxic in high amounts. Do not eat (or allow pets to eat) this ornament! Best to keep in the classroom and hang up as a decoration. The borax solution that the students are handling is fine, though washing hands after the activity would be prudent.

Each student makes a shape out of the long pipe cleaner, small enough to fit in their cup without touching the bottom or sides.
Ask them to include a little hook so that their shape can hang from a half-pipe cleaner laid across the top of their cup.

When the shapes are ready, make the borax solution:
Either make it in each cup: put 3 tablespoons of borax powder in a cup, then fill the cup with recently boiled water and stir to dissolve the powder.
Alternatively, make one large batch of borax solution, and divide among cups. (3/4 cup borax in 4 cups water)
Likely not all the borax will dissolve. That is OK.

As soon as the borax solution is in a student's cup, they can lay the half-pipe cleaner across the top of the cup, then hang the pipe cleaner shape from it, so that their pipe cleaner shape dips into the borax/water solution (but does not touch the sides of the cup).

Leave the cups on a shelf where it will not be disturbed.
As the borax/water cools, box-shaped crystals of borax form on the pipe cleaner. It usually only takes an hour or so for many crystals to start forming. Leave overnight or over a weekend for best crystal growth in all cups. Often, borax crystals start to form on the side of the cup rather than the pipe cleaner - that's OK.

Once enough crystals have formed on the pipe cleaners, wash out the cup, and hang the pipe cleaner shape in the empty cup again, so that the borax crystals can dry.

The borax crystals sparkle in a bright light e.g. near holiday lights or in direct sunlight. On close inspection you can see the flat faces on the bigger crystals of borax.

Put all ingredients in a cookpot and stir until smooth.
Cook over a medium heat and stir until boiling.
Keep stiring and heating gently until it is the consistency of mashed potatoes.
Turn out onto a plate and cover with a damp, well-wrung kitchen towel to let cool.
Once cool knead until pliable.

The clay can be coloured with food colouring, or left white and
painted once it hardens.

When you have made your model, leave it to air dry - turning over every 12 hours or so.
It might take a few days to fully dry.