ingridscience

Directions from the Exploratorium procedure modified slightly:

Students can touch the eye before starting (then they should wash hands before doing another activity).

Cut off the fat. This protects the eye.
Make a small nick in the sclera to let some vitreous humour come out, then cut the eye in half so the front is separated from the back.
Here is the pupil, a hole - you can look through it now. Pull out the iris (black in cows).
The sclera is really tough - it protects the front of the eye - hear the layers with the blade.

Take out the lens.
If it is intact, put it on newsprint to see it magnify the words.
(The lens is good for the students to touch).

[Maybe take a break and add other lens activities in here.]

Look at the back of the eye.
Shiny tapetum in the back of the eye. Cow's are awake at night.
The pink retina converges at the blind spot.
The optic nerve emerges at the back of the blind spot.

Video of a dissection of a preserved cow eye: https://www.youtube.com/watch?v=uJXkrdA87XQ

Assemble the slices of bone into a complete bone. Cues to how they fit together include the outside shape of the bone, the placement of the marrow hole, spongy bone and the hole for a blood vessel.

Marrow is inside bones. Red marrow, in spongy bone, makes blood cells (red and white). Yellow marrow, in the bone shaft, stores fat.

Bone slices like this can be used to make prints, if you are willing to let them get inky.

The best candies to use are the ones that look the same in regular and sour form.
Some chewy candies (e.g. fuzzy peach) have sugar crystals on the outside of the regular form, so they look similiar in regular and sour form.
But for skittles, regular skittles are smooth whereas sour skittles have acid crystals on the outside so they look quite different.

Explain/review with students that anything sour will have a chemical reaction with baking soda, and make bubbles.

Students use the coffee stir stick to add a small scoop of baking soda to each of several wells of their tray. Add water into the wells and stir, to dissolve the baking soda and make a concentrated baking soda solution.

Distribute candies (or a cut piece of a candy if they are large) to the students. If they are indistinguishable from each other, they should be labelled A, B etc.
Students add a different candy to each well of their tray, and look at any bubbles formed. They should decide which candy gives off the most and least bubbles. Then they can predict with candy is the most and least sour.
Taste to check!

If not done already, discuss the chemical reaction:
The baking soda (HCO2) reacts with the H atoms of the sour candy coating/inside to make carbon dioxide (CO2) gas.
Students can use molecular models to figure out the reaction: give them the starting molecules, ask them to make water (H2O) and figure out what other molecule is made. When they use up all the atoms and bonds, and fill all the holes on the atoms, they should arrive at CO2, which is a gas, and makes the bubbles that they see.