ingridscience

This recipe makes just over 2lb.
I make 4X recipe for a class set of playdough.

Mix ingredients together in a pot over low-medium heat.
Stir constantly as the mixture heats up. Keep scraping drying parts from the bottom.
Once it starts to make a paste, remove from the heat, keep mixing until it is all playdough consistency.
Add food dye and knead it in until it is an even colour.
Allow to cool. completely. (It will be sticky the nexy day if you don't. If this happens knead in more flour until it is good again.)
Divide into ziplock bags
Keep bags sealed between uses.

If some of the playdough dries out, just knead it into the mass again.
I have used this play dough for years.

Double this recipe makes enough playdough for a class of 24 students, with a golf ball-sized piece of playdough each.
Four times this recipe (I do this) for a class set with 12 balls of playdough about 2 cups each (~340g each) - see photo.
I use playdough mostly for Fish trap model (one of two stations) and Landform models (students in pairs).

If parts of it dry out, knead in a little water to make pliable again.
Once it dries enough to get too stiff to work, or once the salt starts to crystallize out as larger crystals, discard in a green bin.

If using floral wire, fold one end into a triangle, push through a base or tape to a desk, then wrap it in a large piece of aluminum foil. Bend into a curvy shape. If using copper wire/steel strapping (first photo only) bend them into a curvy shape then attach one end to a desk or base.

Using tape or binder clips, attach the bulb/buzzer then the battery/batteries, from the base of the curvy piece made above.
Then from the battery, add on a longer piece of wire (home-made or purchased), which can easily reach to the top end of the curvy piece.
To the end of this long wire, clip a loop of tin foil or metal.

Test the circuit - when the small metal loop touches the curvy piece the bulb should light or the buzzer should sound. If it does not, redo the connections one by one and check each time for the bulb lighting.

To play the game:
Move the loop from the top of the curvy piece all the way down to its base without touching it. If you do touch it, you will close the circuit and the bulb will light/the buzzer will sound. How far can you go? If it is too easy, make the loop smaller, or the curvy piece more wiggly.

Students make a circuit containing a bulb and a battery, but keeping it open so that they can turn the light on and off by closing the circuit.
Pair students up to send messages to each other.
Give each student a morse code worksheet. Using the worksheet attached, cut half way across the worksheet as indicated, then fold where indicated. The folded up half will hide their message to send from their partner.
Try at first with a very short message or abbreviation.

Discuss the skill required to send and decode morse code fast.

Students build a circuit by taping the components to the board, initially with just a battery and bulb, to test the circuit. The bulb should light when the circuit is closed (makes a loop).
Show them how to open the circuit up, so that they can place objects to test in the gap, to see if they conduct electricity (and therefore light the bulb). They may need to add an additional wire to make components reach.

Provide test materials and/or ask students to walk around the classroom with their board, testing materials that they come across. (They may need to add in an additional wire so that their circuit can reach off the board for testing.)

Summarize together - metals conduct. That is why electrical wires are made of metal.
Plastic, styrofoam, string, paper, wood are insulators so does not conduct electricity. That is why electrical wires are covered in plastic.
A pipecleaner conducts if the wires are attached to the metal inside at each end (but not via the fluffy plastic coating).
Paint is an insulator, so metal objects that are painted may surprisingly not conduct electricity.
Carbon conducts, although not as well as metals. A pencil sharpened on both ends (wires attached to the graphite at each end) should dimly light the bulb. Note that if the graphite inside is broken (from the pencil being dropped) there will be a gap and the circuit will not be complete.

For older students: materials conduct when they have free electrons that can move within the material to make a current. Metals have these free electrons, shared among the metal atoms.

Does water conduct? Try it. No. Why are we so concerned about electrical appliances in the bath? They are with much higher voltage, and it is only a problem if it goes across your heart.
Try other liquids, solutions of kitchen chemicals (baking soda, sugar, lemon juice, vinegar) - also see the electrolysis activity.

From: https://stevespangler.com/experiments/unbelievable-pendulum-catch/

Assemble the device:
Weigh the small nut. Assemble large nuts to weigh 14 times the small nut. (Or separate one washer from a group of 14 washers.)
Cut string or wool to 80cm. Tie the small nut (or single washer) on one end of the wool. Tie the large nuts (or 14 washers) to the other end of the wool.

Hold out a pencil (works better than the straight finger in the photo) and loop the weighted wool over it.
Hold the small nut out to the side (see photo).
Drop the small nut. As it swings downwards, the heavy nuts pull the wool over the pencil, and the small nut wool shortens and wraps around the pencil.
The swinging small nut on the wool has angular (circular) momentum as it is let go. As the length of the wool shortens the small nut goes faster (because the 'angular momentum' has to stay the same). The small nut goes so fast that it wraps the wool completely round the pencil, and keeps wrapping as it gets faster and faster. The tightening of the layers of wool around the pencil creates friction which stops the wool from sliding over the pencil, so it wraps up completely.

Try playing with variables:
How out to the side does the small nut need to be dropped from for it to work?
How long does the small nut wool need to be for it to wrap enough times making enough friction to stop it from slipping around the pencil?
? Measure the smallest angle needed for it to work.
Encourage students to play around, remembering to only change one variable at a time to determine if it affects the outcome.

If the small nut is not held out to the side at the beginning, but straight down, the heavy nuts fall to the floor (as the small nut wool does not wrap around the pencil).

Giant bubbles outside as demonstration.
Students make frame from a loop of string and two straws.
Make own bubbles.
Watch the changing shape and colours in the giant bubbles.

The colours are due to the structure of the bubble skin - two layers of molecules, which separate white light into its colours.

Make a foam drink, by adding air bubbles to milk.

Give students a cup of milk and a straw (and a squirt of flavouring).
Ask them to blow bubbles in their drink to make foam, then drink their "milkshake".

The bubbles are air blown into the drink, which are stabilized by components in milk.

Optional: do the foam molecule test on the component molecules of milkshake (protein, fat, sugar), to find out which ones make the foam. (The fat and protein.)

The foam is a kind of mixture called a colloid.
See the attachment for other kinds of colloids and mixtures.

Pour your bubble mix onto a black plate (about 20ml each). Use a straw to blow as large a bubble as possible (blow long and slow).
Look at the colours. Hold a sheet of white paper behind the plate at an angle to see more colours.
Why are they there? Made by the layers of soap molecules - refer drawing of structure to explain. (Light is made of many colours - when white light bounces of the first layer and the second layer the colours interact with each other and some colours are taken away leaving the others - called interference). So see all the colours in white light.

The colours in oil or on a CD are formed in the same way. Rainbow colours and colours from a prism are also formed from the separation of white light into its component colours, but by a different mechanism (refraction).