ingridscience

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).

Are bubbles always round? What happens if you make another shape with your pipecleaner? Make two shapes. (Optional: add straw for handle.)
Blow and watch others in your group - look for bubbles that are not round. Let me know if you see one.

Why are bubble always round? Show structure of a bubble (layer of water molecules trapped between two layers of soap molecules). The soap molecules can move around, so can the water molecules - they are elastic. They move until find most stable shape: for one bubble this is a sphere.

Make bubble mix - this is the recipe that science world uses.
Smell the tube. What is in it? Baby shampoo. It’s soap. Soap makes bubbles.
We’ll add the same amount of water. What number do we add water to?
Mix it with the stick, then put the lid on, and gently invert to mix. Do not shake.

Now we have our bubble mix.
The simplest bubble blower is a straw.
Students dip their straw in bubble mix, take it out, and blow bubbles (they will generally be quite small).
Challenge: How can you make lots of small bubbles, or one large bubble. Control how you breathe.
While you are blowing, figure out what each bubble actually is. (Air inside a layer of soap.)
The soap molecules can move around within their layer, to settle at the most stable shape: a sphere.
If you make many small air bubbles that pile up, you make a foam (a kind of colloid mixture that is bubbles of gas trapped in a liquid (the soap mix)).

Look at the commercial bubble blower. What is the difference between theirs and ours that might make more bubbles? It has more places for the bubble mix to sit - so can make bigger bubbles.
Try making a pipecleaner blower, which should hold more mix: make a loop at the end of a pipcleaner. (Optional: push the straw on the long end for a handle.)
You should be able to make more and/or bigger bubbles because the pipecleaner fuzz holds more bubble mix.

Students are instructed to search for the items on their bingo card within a designated area.
Students call Bingo! when they have found all the items on their sheet.

Students look closely at sand and find the colours in it. They can tape a sample in their notebook, use a magnifier to look at the grains closely, and list the colours that they find.

Students rub a smear of mud onto their worksheet, allow it to dry for a few seconds, then add a piece of tape over it.
They use a magnifier to look at the sample closely, then estimate how many grains of mud could fit into a grain of sand.
See particle size chart at: wikipedia.org/wiki/Particle_size_(grain_size)

Discussion that sand (and mud) are made from rocks broken up by the waves.
Students look for larger rocks of the same colour on the beach, that may have been broken into sand/mud. Teacher can name them: basalt is black (igneous rock), granite is speckled and can be broken into its mineral components: quartz (clear/white), feldspar (pink), mica (shiny flat black).

Students can look for other debris in sand, especially parts of shells.
Discussion that the shells of the animals become sand as they are broken up by the waves.
Students can sieve sand to find more broken shell pieces, and tape them in their notebook.