ingridscience

See a real animal pelt and feel real fur.
Find the underfur (in bear fur) that keeps them warm, and the guard hairs that keep off rain and dirt.
Use a magnifier to look at the fur closely, and a ruler to measure the length of the hairs.
Compare to our own hair.

We wear clothes that have the same job as animal fur.

Some animals also have a thick layer of fat (e.g. bear has 4cm). Compare to our own layer of fat.

Use a metre stick to measure a template of a black bear, and find out how tall and how long a bear is. (It is on all fours, 2m long and 1m high). Record it on a worksheet.

Stand next to the bear template to compare its size to their own (are you taller/shorter, narrower/wider) and measure your own height if time and able.

Students fit their foot into a bear print, to compare sizes.
Students look at a model of bear claws and compare their size to their own nails.
They can use space on the worksheet to draw the bear paw or claws.

Students add a drop of methylene blue (or iodine) to a slide.
Students scrape cheek cells from the inside of their cheeks using a toothpick, then spin the toothpick in the drop on the glass slide to shake them into the methylene blue.
Lay a cover slip over the drop with cells in it.
Look at the cheek cells under low power to start to find the cells.
Then increase the power, keeping a good-looking cell in the centre when moving up to the highest power.
Look for the nucleus in the centre of the cell.
With methylene blue, other cell organelles are also visible, and sometimes bacteria (dark blue spots outside the cheek cells).

Lower the room lights, so the classroom is dim.
This activity works best with student pairs.

Lay the circle of dark cloth on a desk, leaving space for one student's chin to rest on the desk in front of it. They will stay there and observe the Moon phases.
The other student manipulates the materials:
Place the foam ball 'Moon' on its stand at the edge of the cloth.
Place the flashlight at the centre of the cloth, shining on the 'Moon'.
The observing student should see that the Moon is bright where the flashlight hits it and reflects off to their eyes, and in shadow where the 'sunlight' does not reach their eyes. The bright part will be a classic Moon shape: a crescent, half, nearly full or full Moon. Or it could be in total shadow if the Moon is nearest to the student with their chin on the desk.
The student manipulating the materials moves the Moon to all points around the edge of the cloth (rotating the sun to follow it), so that the student observing sees all the phases of the Moon. It is important that the observer keeps their chin in the same place.

Then switch roles: the other student puts their chin on the desk and looks at the Moon phases through its 'orbit', while the second student manipulates the Moon and keeps the Sun shining towards it.

Note the real Sun is shining light in all directions, but the flashlight has to be turned around to model this.

Show students how to secure the string to a chosen object so that it can hang freely, feeding the free ends of the string through the loop to hold it tightly if necessary.

Then wrap the free end of the string three turns around each index finger and push the finger against the flap of each ear (the tragus).
he ears are blocked so do not hear any sounds through the air, and the sounds coming up the string will be heard through the bones of the finger and the jaw.
(Practice with the string only at the carpet to check that students are pushing against the right part of their ear.)

Lean over and swing the object so that it bangs against a table or chair, which starts it vibrating. You only hear sounds coming up the string, through your finger and then through your jaw bone into your ear... and not through the air.

Students can anecdotally share their observations at the end, or use a worksheet (see attached below).

Questions to prompt students with experimentation:
What was the difference between objects made of different materials (e.g. plastic and metal)?
Try making the ringing sound, then touching the object or string to stop the ring.

After students have successfully heard some sounds through the string, ask them to compare with the sounds through the air. Swing and bang an object, but do not cover your ears.

What is happening?
As you bang the object it vibrates. The vibrations travel up the string to the bones in your ear, where you hear them as a sound that has passed only through solids. Different materials transmit vibrations differently and so the sound changes.

Objects that have a molecular structure that can vibrate and resonate more (i.e. metal) make a longer, ringing sound than plastic or metal.
Sounds through the string sound deeper and more resonant than sounds through the air, because the solids can transmit the lower frequencies (lower notes) than air.

To hear sound through another solid, lay your ear flat on a desk. Knock on the other end of the desk with your knuckles.

Animals hearing through different materials
Just as the sound is quite different through the string compared to through the air, animals that hear sounds through water or the ground hear sounds quite differently from us.

Sound travels faster and further through liquids (e.g. the ocean) and solids (e.g. the ground), than the air. But more energy is needed to transmit sounds through liquids and solids, so very quiet sounds do not transmit well.

Animals that hear sounds through the water:
Fish and marine mammals such as whales, dolphins. Lower frequencies travel well under water, and a long way.

Animals that hear sounds through the ground:
Snakes lack external ears and internal eardrums. They hear through their jaws (two jaws - can hear in stereo), the sound going directly to the cochlea. They bury themselves in sand to make their hearing more precise.
Elephants detect these seismic waves with the skin of their feet and trunk. Communicate danger from miles away.
Blind mole rat knocks its head against the walls of its tunnels to signal to its neighbors.
Termites in danger will bang their heads on the ground, which spreads like a chain reaction through the colony.
Kangaroo rats drum their foot on the ground with danger.
Frogs and spiders also hear through the ground.
https://blog.nationalgeographic.org/2013/11/14/good-vibrations-7-animal…

This models how sound travels by moving vibrations.

Pairs of students stretch the slinky (or space phone) between them on the ground.
At one end, quickly push the slinky to compress a few of the turns. The compression, if tight and fast enough, will move along the slinky.
See how the vibrations move along as a wave, as one part of the slinky pushes the next part.
This is how sound waves move: molecules bump the next molecules along, forming a wave of vibrations.
These are called longitudinal waves, and is how sound moves through solids, liquids and gases.

With the space phone the added cones mean that the sound of the coils vibrating are amplified, to make a strange, spacey sound.

Make a transverse wave by flicking the slinky quickly sideways. The wave will move along the slinky.
(This kind of wave is often easier for students to make.)
Light waves move in a transverse wave.

Look for the wave coming back along the slinky, which models an echo. An echo in a big room, or across a valley, is the sound waves bouncing back.

When these vibrating molecules reach our ear, they make our ear drum vibrate which transfers the energy vibrations to our inner ear where they stimulate neurons. The nerve fires and sends a signal to our brain, that we perceive as sound.