ingridscience

Give students the bones and ask them to assemble them into [a leg] with the appropriate amount of guidance.
Compare with equivalent human bones for size and shape.
Look at the different joint types - ball and socket, hinge.

A cube-shaped bubble can be made for a demonstration, or by students:
Use pipecleaners to make a cube. Dip in bubble mix. Wet a straw in bubble mix and blow into the centre of the frame, to make a cube-shaped bubble.

Pour about 20ml bubble mix onto a plate. Use a straw to blow bubbles in it.
By blowing bubbles next to each other you can make shapes that are not round: hexagons, pentagons and other shapes.
Round is most efficient on their own, but other shapes are more efficient when they are packed together. What shapes can you make?
What do the hexagons remind you of? Honeycomb. A good shape for packing.

Pour some coloured bubble mix in a tray/cup. A cup will need less mix, but a tray is more stable.
Blow bubbles in the paint/bubble mix with the straw.
Lay the paper over to make a bubble print.
Repeat in another colour paint/bubble mix.

Prompt students with questions to help them observe the bubbles closely if necessary:
What shapes are the bubbles on their own and when next to each other?
What happens to the shapes if a bubble is popped?

Science of bubbles can include:
the shapes of the bubbles (separated and attached) and how they fall into the most stable configuration;
the structure of bubbles - the skin is a layer of water molecules between two layers of detergent molecules, which encloses a pocket of air molecules.

Please note that in a class of students it is likely that one of them is at least partially colourblind (1 in 12 males are colourblind). As this is an activity distinguishing colours, these students will not be able to tell some colours apart and perceive some colours differently, although the activity will be no less interesting for them. The common red/green colour blindness means reds and greens (or colours containing reds and greens such as browns) look similar. More information at colourblindawareness.org and colorblindguide.com/post/the-advantage-of-being-colorblind.

Chop/cut the red cabbage leaf into small pieces, and put in the heatproof container. Pour boiling water over the red cabbage pieces. Let the cabbage pieces soak in the hot water for 5 mins or more, while stirring with the spoon. (The longer it soaks, the darker the dye will become. Overnight will give the darkest dye. The dye can be stored in the fridge for a week) There is a physical change as the dye moves out of the red cabbage pieces into the hot water.
Pour off the red cabbage dye into bottles.

Making an infusion in hot water, like this, is one way that plants are prepared for use. Here are other indigenous ways of reparing medicinal plants:

Red cabbage dye as an acid-base or pH indicator
Aliquot the dye into squeeze bottles for adding to separate wells of a white tray (or use the spoon).
The dye turns pink when an acid is added to it, and blue if a base is added to it. Something that is neither acidic or basic (e.g. water) will leave the dye purple.
Try adding household materials to the dye, to find out if they are an acid or a base. Best are those that are colourless or a light colour, so they don't mask any colour change in the dye.
To more accurately determine the pH of household materials, use the colour spectrum on the pH testing worksheet (attached below). The lower the pH, the more acidic. The higher the pH, the more basic (or alkaline). Students can try individual liquids to test, and then go on to test mixtures of liquids. Their results can be graphed for discussion of which materials are more acidic and which more basic, as well as other patterns that come out of the graph (e.g. outliers). Students can also mix household liquids to find the emergent pH. Chemists, biologists use the pH scale to test chemicals and water for how acidic or basic they are.

Optional for older students - explain the pink/purple/blue colour changes in terms of molecule structure:
Show students the structure of two dye colour molecules (see red blue pigment molecules file attached) - one is the colour molecule when cabbage dye is pink or red, the other the colour molecule when the dye is blue . Challenge them to spot the difference between them (one of them has an extra white hydrogen atom top left). This tiny difference between the two molecules makes them different colours - in acids there are extra hydrogen atoms around and the dye molecules gain a hydrogen, so turning the dye pink or red. In a base, the dye molecules lose a hydrogen atom and so turn blue. When the dye is purple (at neutral pH, between an acid and a base) there is a mixture of red and blue dye molecules, so making the dye purple.

The reason the red cabbage dye turns green at high pH values is due to another pigment molecule, an anthoxanthin, which is colourless until high pHs, when it turns yellow. The mixture of the yellow anthoxanthin and the blue anthocyanin at high pH values gives the green colour.

Extension - relating to sour foods:
Foods that are sour are acidic, so you can find out if something is sour without even tasting it! If it turns the dye pink it will be sour. (Some sour foods, e.g. lemonade, have a lot of sugar added to them which combines with the sourness to make a pleasant mixture.) See sour foods activity for more detail on testing foods with red cabbage dye.

Red cabbage as a paint or fabric dye
Painting - paint the juice onto paper and let dry, then paint on it with acid/base with Q-tips.
Dyeing yarn - use acid/base to vary the colour of larger batches of red cabbage dye and add yarn to it (mordanting the wool before hand should make the dye stick better - see notes). Very gently squeeze extra dye out, then put individual yarn pieces in little pots to dry. Do not rinse with water as the dye will come out. Make contrasting colours then twine to make a bracelet.
Dyeing cloth - add to batches of dye or drip acid/base onto a piece of fabric dyed with the purple red cabbage dye. Lay cloth out on cardboard to dry.

Plant dye extraction activity: extraction of dyes from plants including native plants.

Using a cut flower:
Cut the stem of a white carnation (or other white flower).
Stand the flower in a tube of food colouring for an hour or more (test to check).
Watch for the petals turning the colour of the food dye.
Cut the stem after colouring (to remove mess).

Using one petal:
(See attached booklet used at the NY Hall of Science museum.)
Cut the pointed end off a white petal. Stick the petal on a piece of tape, with the cut side hanging over the edge. Make sure the petal is lying flat on the tape.
Fold the paper lengthwise and bridge across two thin books, so there is a small gap underneath the strip of paper. Arrange so that the fold of paper is the low point.
Stick the petal to the white paper, so that it hangs off the bottom of the fold of the paper, with its cut side just touching the table.
Put a piece of wax paper on the table, in front of the petal, then drip a drop of food color onto the wax paper.
Slide the wax paper under the petal, so that its cut tip dips into the food color.
Watch for several minutes to see the food color creeping up into the petal. It traces out the vessels in the petal, which carry food molecules to all parts of the petal. The vessels extend down the stem of a flower, allowing transport of water and nutrients throughout the plant.
Unfold the paper and put another piece of tape over the rest of the petal, to stop the food color from making a mess.

Sometimes these branching patterns can be seen naturally in flowers. (see purple petunia photo)