ingridscience

Give the students their ears.
When their ears are on their head they are a coyote.
To be a rabbit, students turn one of the ears down, floppy bunny ear-style.
To be grass, students put their ears around their necks out of the way, squat down and put their fingers up like blades of grass.

Divide the students into different species for the first round of the game: about 10% of them are coyotes (wearing ears); the rest of them split between rabbits (with floppy bunny ears) and grass (ears around necks and fingers up).
Divide the area into three parts. The coyote territory is in the middle, the rabbits on one side, the grass on the other side.

When the teacher signals the start of a day (or more realistically, a month), the rabbits try and run across the coyotes territory to get to the grass. The coyotes try and catch them by tagging them as they run across. If a rabbit does make it across the coyote territory, it needs to find a grass of its own.

Initially at least, once the rabbits have made it across, or not, the teacher signals the end of the day, and the class discusses what has happened and resets the characters as follows:
If a rabbit is caught by a coyote, the coyote gets to eat and reproduce: the rabbit becomes a coyote for the next round.
If the rabbit makes it across the coyotes’ territory, and finds its own grass to eat, it reproduces: the grass it pairs with becomes a rabbit for the next round.
If a coyote does not catch a rabbit, or a rabbit does not find their own grass, they die, and recycle into the earth: they become grass for the next round.
At the end of the round, all rabbits walk back across the coyote territory unchallenged to their starting side.
If the students get the hang of becoming a new species each round, try running the game continuously: they switch out their ears/tail/grass as they become a new species each time. Rabbits can walk back across the coyote territory unchallenged before attempting to run across without being caught to reach the grass.

Run the game for several rounds, maybe stopping earlier if one of the living things dies out (or not - to see how the other populations are affected).
Discuss what happened: the individuals that are able to eat can reproduce. If there are a lot of one species, the food that they eat becomes depleted, then there is competition for the less food available, and not as many of that species are able to eat and survive, so their population decreases again. This game shows population changes in action. Sometimes a species may die out, and the populations of the other species it interacts with in the food chain take over.

Add in an adaptation, showing natural selection:
One rabbit gets a random mutation in its DNA that makes it run a little faster than the other rabbits. Signify this by adding a clip or other marker to the headband of one rabbit. In the game this rabbit with a mutation gets to cross the coyote's territory without being tagged. If it finds its own grass it can reproduce to make another rabbit, also with the "fast" mutation (add a clip to the headband).
As the days past by, more and more of the rabbits that survive have the fast mutation. It is a beneficial adaptation that has spread through the population. This shows natural selection - how beneficial mutations are selected for.

Discuss other adaptations in coyotes and rabbits that help them survive:
The coyotes have teeth and claws to catch their prey, large ears and good noses to locate prey etc
The rabbits have long legs to escape from predators, also large ears to listen out for danger etc
Both animals are camouflaged to blend in with their surroundings. For the rabbit, a prey animal, it can hide in the grass better and not be spotted by a coyote. Coyotes are camouflaged so that they can sneak closer their prey without being seen by them.

To make the rocket:
Roll the cardstock snugly around the stiff tube, then tape along its length to make it into a tube. Slide the cardstock tube off, flatten one end, and tape it closed with packing tape. Optional now or after launching a few times: decorate/add rocket fins etc.
To make the launcher:
Pull the bike inner tube over the mouth of the plastic bottle and secure with duct tape. (Or push the PVC tubing inside the mouth of the bottle and secure with duct tape.)
Pull the other end of the inner tube over one end of the stiff tube and secure with duct tape. (Or push the other end of the PVC tubing inside the stiff tube and secure with duct tape.)

To launch:
Take the rocket outside, or into a gym/hallway with a high ceiling.
Slide the cardstock rocket over the stiff tube, point away from people, then stomp on the water bottle.
To reinflate the water bottle, blow down the stiff tube, before putting the rocket on again for relaunch.

Replace plastic bottle once this one stops working - try a bigger bottle (e.g. 2 litre), although stiffer plastics tend to crack sooner.

Add fins to the tube to make it fly straighter and higher.

Build with PVC tubing: https://www.youtube.com/watch?v=za_2uj1mbyw

Discussion in terms of molecules:
When the plastic bottle is stepped on, the air is pushed out of the bottle and into the tubing next to it, creating an area of high pressure (i.e. the molecules of air are closer together). This high pressure region moves along the flexible tube (molecules always move from high to low pressure areas), and into the stiff tube. When the high pressure molecules exit the stiff tube, they hit the cardboard rocket and push it upwards. The pressure is great enough to exert a force that sends the rocket high into the air.

This activity needs quite a dark area, so give students a while to get their eyes adjusted to the dark first.

Place a wintergreen lifesaver on the cloth under the piece of plexi.
Smash the plexi with a hammer.
As the candy gets broken into small pieces, flashes of blue light are seen in different places under the plexi.

Young student explanation: when you hit the candy you put in energy. The energy comes out again as light. It is lightening on a very small scale.

Older student explanation: As you hit the candy you separate charged particles. As electricity flows between them it excites the nitrogen in the air. The excited nitrogen re-emits the energy as light - mostly UV but some blue. This happens with regular sugar, but the light emitted is mostly UV so not so visible. This is the same chemistry as lightening. The wintergreen flavour amplifies the light - methyl salicylate is a fluorescent molecule: it absorbs the UV emitted by the nitrogen and re-emits blue light, so making the light given off more in the visible range where we can see it.

When you shine light on these items they glow. The UV light gives fluorescent molecules extra energy. They release this energy again as light.
(Older students: discuss how electrons move to a different energy level when excited by the UV light, then release photons of a different colour light as they return to unexcited state).

Fluorescent markers only glow when the UV light hits them - the fluorescent molecules release the light energy right away.
Glow in the dark object release light after the UV light is taken away - the "phosphorescent" molecules in them release light slowly.

Some rocks are fluorescent. See photo of calcite fluorescing pink.

Explain that inside the plastic of the light stick is a glass rod. One chemical is inside the glass rod and another is outside. When you snap the glass rod by bending the light stick, the chemicals mix together, and the chemical reaction produces a new molecule that glows.
Turn the lights out, then ask students to snap their sticks all together. Ask students to look closely as the chemicals mix - they should be able to see a swirl of colour as the chemicals react and new coloured glowing molecules are made.
First photo shows the chemicals mixing and making light.
(Older students: the tube contains hydrogen peroxide, which mixes with a chemical outside the tube. Two chemical reactions result in the dye getting excited as it gains energy. It releases this energy again as light. Additional dyes make the glow sticks different colours. See Wikipedia entry for more details).

Ask students to find out how heat and cold affect the rate of the chemical reaction in their light sticks, by dipping the light sticks in the warm and iced water tubs.
They should have found that in the warm water the light stick glows more intensely. This is because the heat energy causes the molecules in the light stick to move around faster, hence collide more often and chemically react to make more glowing molecules.
The light stick dipped in cold water should become dim. Heat energy leaves the lights stick and moves into the cold water, hence the molecules in the light stick have less energy and move around less. The cooler molecules collide less frequently, so undergo fewer chemical reactions to make glowing molecules.
(Sometimes students see something different, possibly due to the intensity of the glow stick affecting the sensitivity of our eyes in the darkness. These are real results as they are what the students found, but during discussion focus on what the majority of the students found.)

Students can make bright and dark stripes along their glowstick by dipping in one tub, then dipping it not as far into the second tub.

Discuss how the chemicals are used up when it glows brighter, and how they can preserve their glow sticks by putting them in the freezer overnight to slow the chemical reaction down.

Students can draw the candle while it is burning, to notice the different colours of the flame, the liquid wax below the wick etc.

State changes in the wax:
Solid to liquid to gas. The solid wax melts with the heat of the flame, and the wick draws the liquid wax up by capillary action. Once the wax is a gas it can burn.

Energy transformations with a candle:
Chemical energy of the candle wax is converted to light energy and heat energy.

Chemical reaction of a burning candle:
Place a jam jar over the candle - it burns for a while then goes out. Students get quite engaged anticipating when it will go out; the flame can be fast revived by removing the jar at the last second.
The wax needs oxygen from the air to burn. Also note that water condensation builds up on the inside of the glass.
Place differently-sized jars over identical burning candles, to see that the candle with the larger jar will burn longer (as there is more air in it).

The molecules in the candle wax and oxygen from the air combine and rearrange, and release heat and light as they do so.
Optional: students use molecule models to visualize a simple version of the chemical reaction: CH4 + 2O2 → CO2 + 2H2O. Called combustion. The reaction product water is visible on the inside of the glass in which the candle burns.
Paraffin wax is actually longer chains of C and H atoms, called alkanes, with average 25 carbons. Optionally start with a long hydrocarbon chain and break off a CH2 for each student from the chain (instead of a CH4); students will then need to share the second oxygen as they will have two less H atoms.
The chemical reaction of the whole chain with oxygen would be C25H52 + 38 O2 → 25 CO2 + 26 H2O. The generic chemical formula of wax is: C(n) H(2n+2). The wax combines with more molecules of O2, to release the same products.)

Cover identical candles with differently-sized jars at the same time. Ask students to predict which one uses up oxygen first. (Students need to estimate the relative volumes of the jars.)

Candle trick:
Once the flame of a larger candle has been lit, it can be blown out, then relit from a height above the wick. The wax vapour still in the air ignites, which then relights the wick. The flame must be quite big for this to work.

Additional information on flames:
The flame is a mixture of hot gases, primarily CO2, water vapour, oxygen and nitrogen.
The yellow colour of the flame is due to soot particles glowing because they are hot (black body radiation). Other colours in the flame are from transient reaction intermediates during combustion such as the Methylidyne radical (CH) and Diatomic carbon (C2). These molecules are excited, then emit blue and green visible light (spectral band emission).
https://en.wikipedia.org/wiki/Flame
Try burning copper sulphate or other chemicals to make other flame colours.

For more detailed chemistry of a candle burning see the ChemMatters issue on candle chemistry: http://chicagoacs.net/statefair/CD-2008/Chemmatters/2007_12_smpissue.pdf
or https://candles.org/candle-science/#:~:text=The%20heat%20of%20the%20fla…(turns,carbon%20dioxide%20(CO2).

Add a couple of drops of indicator dye to the water in the cup to measure the pH of the water. It should be around 7.
Add some carbon dioxide to the water from breath: either blow through a straw into the water, or blow into the tube and then shake the exhaled air into the water (repeat blowing into the tube and shaking as necessary), until the colour changes.
Read the new colour of the water on the pH chart - it will have dropped i.e. become more acidic, to about pH 6.

The acidification of the water is reversible: waft in fresh air and shake it into the water. This air has less CO2 than our breath, and slowly, as more air is wafted into the tube and shaken into the water, the pH of the water will return to neutral. It will take longer than acidifying the water in the first place.

Climate change and ocean acidification
The water in the tube absorbs the CO2 from your breath, just as the oceans absorb increased CO2 in the Earth's atmosphere. As the CO2 in the water increases, the pH of the water falls - it becomes more acidic.
As we increase the amount of CO2 in our atmosphere through emissions, we are acidifying our oceans.

Ocean has changed by 0.1pH unit, which is a 30% increase, since the industrial era.
Lakes are more variable because of the rock type they are in, but they are also becoming more acidic.
Many chemical reactions, including those that are essential for life, are sensitive to small pH changes. (In humans: blood pH must be 7.35 - 7.45. Blood pH drop of 0.2-0.3 causes seizures, comas even death.) A small change in seawater pH affects marine life, especially marine life with shells: corals, mussels, clams, oysters, urchins, zooplankton (tiny drifting animals). Their shells become fragile and they die.
A tiny change in acidity has a profound effect on ocean life, and so food chains.
See website: https://ocean.si.edu/ocean-life/invertebrates/ocean-acidification#:~:te….
Luckily ocean acidification is reversible. So if we can reduce the CO2 in the air the ocean water pH will rise again.

A dramatic climate change and ocean acidification event happened during Earth's history, and is evident in ocean bed core samples.
The Paleocene-Eocene Thermal Maxiumum (PETM) was a major greenhouse warming event 55 million years ago, resulting from a massive carbon release into the atmosphere (likely methane as well as CO2) which acidified the oceans. Ocean bed core samples show that this increase in greenhouse gases led to a sudden decrease in shell deposits (e.g. https://www.ecord.org/website/wp-content/uploads/2016/02/replica208a.jpg Also image here or here) - the shells of ocean animals dissolved in the more acidic ocean water before reaching the ocean floor, and the core samples showed just red clay. The greenhouse gases we are currently releasing into the atmosphere are at a much greater rate than this previous greenhouse event, and will lead to a similar effect on ocean life. Life in the oceans is linked to all life on Earth, so if we affect ocean life by acidifying ocean water, there will be knock on effects to all life on Earth.
But, there is hope!
As the students waft fresh air into their tubes, the acidification of the water will reverse and it will return to pH 7.
This shows that ocean acidification is reversible. If we can lower our emissions to reduce the CO2 in the atmosphere, the oceans will recover.

Blood CO2 levels affect our brain and heart response
When you exert yourself you need more oxygen. You also release more CO2, which makes your blood more acidic. A part of the brain called the medulla oblongata measures the pH of the blood, so can determine how much CO2 is in the blood. Once the acidity gets to a certain level, the medulla oblongata signals your body to speed up breathing and to increase heart rate. Increased heart rate will increase O2 levels in the blood again and also remove the excess CO2 from the blood.
(You can use the cortex of your brain to override and slow down breathing by thinking about it.)