ingridscience

Students in pairs. One student closes their eyes and the other one uses a Q-tip to put one of the tastes on their tongue.

Version 1: students guess which taste type the liquids are (salt, sweet, bitter, sour or umami).
Version 2: students put 6 liquids in pairs by their taste (sour, sweet, salt)

A good opportunity to teach that the tongue is NOT divided into different areas of taste sensitivities.
A good opportunity to introduce tastes other than the familiar 4 e.g. umami. Can also discuss spicy as a taste/pain sensation.

Procedure A makes a soda drink with orange juice and baking soda. The students find out where the bubbles come from. Good for all ages.
Procedure B compares the amount of bubbles made when baking soda is added to different juices. Students learn about acidity. Best for intermediates.

Procedure A. Make soda drink:
Fill a dixie cup with juice. Drink a little of it to see what it tastes like before the experiment.
Scoop up about 1/8 teaspoon of baking soda, using a tiny scoop or a coffee stir stick. Tip it into to the cup of juice and stir it in. Look carefully for tiny bubbles rising to the top of the liquid. Listen for bubbles popping on the surface (quiet is needed to hear them). Taste the juice again - the juice should be fizzy.
Discuss the state changes during this chemical reaction: a liquid and a solid produced a gas. The gas bubbles stayed in the liquid, to make the drink taste fizzy.
The specifics of the reaction can be discussed: the bubbles are carbon dioxide, formed by the chemical reaction between an acid (the juice) and a base (the baking soda).

Optional molecule modelling of the reaction:
Give students molecule models of the molecules in baking soda and orange juice. Ask them to figure out the new molecules that are made when the baking soda and orange juice mix, by taking apart these molecules and rearranging the atoms to make new molecules. Give them a hint that one of the new molecules is water (show a model), and ask them to use up all the rest of the atoms and bonds to make the other molecule.
HCO3 (baking soda) + H (orange juice) —> H2O (water) + CO2 (carbon dioxide gas)
See the molecule photo above. Note that the CO2 molecule has two double bonds - students may need prompting to fill up all the holes in the atoms to complete this molecule.
Once all students have made their water and CO2 molecules, name the carbon dioxide molecule and ask if students have heard of it. Tell them that it is a gas, and this is what makes their soda drink fizzy.
The chemical reaction they just modelled, is the same as what is happening when they make orange juice and baking soda to make their soda drink.

Further discussion on soda drinks and acidity:
Canned sodas are fizzy because they have carbon dioxide gas in them. Soda fountains inject carbon dioxide gas into drinks.
Anything that has free H atoms (ions) is acidic and tastes sour. The more sour it tastes the more H ions it has e.g. lemon juice has more H ions than orange juice. We add sugar to drinks to mask the sour taste.

Procedure B. Make soda drink, then compare different juices:
Start by making a soda drink with orange juice, as in Procedure A.
Students use molecule models to figure out the chemical reaction that made the bubbles of gas:
Give them the starting molecules, and ask them to rearrange the atoms and bonds to figure out what molecules are made (given them a hint that one of the end molecules is water).
HCO3 (in the baking soda, or base) + H (in the juices) —> H2O (water) + CO2 (carbon dioxide gas)
See the molecule photo.

Then compare different juices for how many bubbles they make with baking soda:
Some juices have fewer H atoms in them, so when baking soda is added, they will make fewer CO2 molecules. Therefore fewer gas bubbles are made. Juices with more H atoms in them can make more CO2 molecules, so will make more bubbles of gas.

Give student groups squeezy bottles of the juices, three 15ml tubes in a rack (one tube for each juice type), baking soda in a pot with a mini scoop, and optionally a workhseet (see attached document; print double sided; half sheet each).
Students write on some paper under the tubes to record which juice will go in which tube, then add 5ml each kind of juice to its respective tube.
They then add one mini scoop of baking soda to a juice, use a stir stick to mix the contents quickly, then remove the stick. Use the numbers on the side of the tube to record where the bubbles rise to for each juice type.

While allowing students to keep experimenting with mixing different juices, bring each group in turn to the board to graph their single-juice results, juice type on the x-axis and ml the bubbles rise to on the y axis. There will be variation between the groups, but that is expected with real data collection, and outliers can be used to demonstrate how data is rarely completely tightly grouped.

Class discussion while looking at the graph:
Which juice makes most bubbles [lemon juice], which the least [apple juice]?
Refer back to the chemical reaction: the juice that makes the most bubbles of carbon dioxide must have the most H atoms in it (as the amount of juice and baking soda was the same each time - the only thing that changed was the kind of juice, hence the number of H atoms). Hence the lemon juice has more (or a greater concentration of) H atoms in it, apple juice the least, and orange in the middle.

The number of H atoms in a juice determines how acidic it is, which is the same as how sour it is.
So fewer H atoms means less acidic and less sour. And more H atoms mean more acidic and more sour.
Which juice would you predict is the most sour? (The one with the most bubbles, as it would have more H atoms.)
Students can taste each juice to test if the juice with the most bubbles is also the most sour. Lemon juice will certainly be very sour, and apple juice not sour. A complication is that sugar is added to juices to offset the sourness, so cranberry juice, which is very acidic, and will make lots of bubbles, may not obviously taste the most sour. Students may be able to detect the sourness of cranberry juice behind the sweetness.

After looking at the graph together, or while groups are bringing their data to the graph, allow students to experiment with mixing juices to compare bubbles made. Encourage them to think about how much of each juice they are adding and make predictions about the bubbles that will be made.

Dough will rise as a chemical reaction happens in it: a gas is made, and the bubbles push out on the dough, making it rise.
Experiment with the ingredients to find which ones that make a gas and make the dough rise. You might have an idea already and can test your idea.

Either do as a group, with the students suggesting combinations (up to two ingredients; can include oil) and the teacher setting up the tubes as a demonstration.
Or student groups do their own (skip the messy oil):
Use a worksheet (attached below). Choose a number in the table (attached below), then find the corresponding pair of ingredients.
Add 1ml of each of the ingredients using the stir sticks (do not use the same stir stick in different ingredients).
Then make other tubes for other pairs of ingredients.

Once all the tubes are ready with their dry ingredients, hand out bottles of warm water.
Fill to the 7ml mark and use a new stir stick to stir well.

Wait at least 5 mins for results, then ask students to observe/record the ml of gas in each tube in the table (or write on the board from students' observations, see photo).
Ask students to compare their data to conclude which combinations make the most, and some gas.
Expected results:
The yeast and sugar make enough gas for bubbles to likely spill over the top of the tube.
Yeast and flour make some gas bubbles too.
Yeast and flour/oil/salt make very few or no gas bubbles (probably because the yeast has some sugar stored in it already).

Explanation:
The yeast breaks apart sugar molecules to form ethanol (which evaporates off) and carbon dioxide gas, which makes the bubbles. (Chemical reaction can be modelled.)
Flour is made up of chains of sugar molecules. The yeast can break up these chains, then make gas from the sugar molecules.
Yeast has some sugars stored in it, so can make a few carbon dioxide bubbles from these stores.

Smell molecules posting game
Spread pots around the site, each displaying a smelly molecule image. They should be placed near the plant that releases their smell molecule, or bring in plants to place next to each pot. I used these smell molecules and plants (molecules pictured in attached file "table of smell molecules and plants for posting game"):
A sprig of rosemary next to a pot displaying the eucalyptol molecule.
A sprig of lavender next to a pot displaying the linalool molecule.
A sprig of lilac (or any sweet-smelling flower such as rose or geranium) next to a pot displaying the geraniol molecule.
An apple (or banana or other ripe fruit) next to a pot displaying the isoamyl acetate molecule.
Next to some grass (or any green leaves that release the mown-grass smell), place the pot displaying the hexenal molecule.
Next to a cedar (or other evergreen tree), place the pot displaying the pinene molecule.
Other ideas for molecules and source match: https://www.thoughtco.com/aroma-compounds-4142268

Shuffle the molecule cards, then give one to each student, but ask them to wait until everyone has a card before starting. Instruct them to post their card into the pot with the same molecule on the top. Some of the molecules look similar, so they should check the match carefully. Ask them to also smell the plant next to the pot to see what the molecule smells like.
The students can start out all at once. As they each return from posting their molecule card, give them another card to post. Keep distributing the cards, one by one to the students that return, until all the cards are posted. (Or end earlier if needed.)

Discussion:
Bring all the pots back to the group, and ask students which molecules looked similar to them (e.g. eucalyptus and pinene, or linalool and geraniol). Although they look similar they have different smells. Our nose can distinguish between the smells by this mechanism: each smell molecule fits into a different molecule in our nose. Once the smell and receptor molecule dock with each other, they trigger a neuron to fire which sends a signal to our brains to sense a smell. (Actually it is a little more complicated as smells are usually made up of more than one smell molecule, and the combination of receptor molecules that are triggered induces the distinct smell sensation in our brain.)

Discussion on how plant smells are used to communicate with animals:
Sweet smells are given off by flowers to attract pollinators to them.
Smells like eucalyptus and pinene repel insects, to discourage insects from eating the plants that release them.
The ripe fruit smell (isoamyl acetate molecule) attracts animals to eat the fruit (and hence distribute the seeds in them).
The grass smell (hexenal) is made when green plants are crushed or damaged. It is thought to induce defence responses in neighbouring plants so that insect damage to them is limited.

Pollinators posting game
Short discussion/review on why flowers are different colours, smells and shapes - to attract different pollinators. The pollinators collect nectar and/or pollen from flowers for themselves. At the same time they brush against pollen and move it from one flower to another, so fertilizing the eggs, and making seeds.
Bees, butterflies, humming birds, moths, flies, beetles and bats all pollinate flowers. Some flowers are pollinated by only one kind of pollinator, and some are pollinated by many kinds. (Wind is also used by many plants to simply blow the pollen between them.)

Place pollinator pots, each displaying an image of a pollinator, next to a flower that the animal would visit (or bring in flowers to place next to the pots):
Bee - attracted to bright coloured flowers with a sweet smell. The flower can be any shape, including tubular as long as the bee can fit into it. (They also use nectar guides: visible or UV patterns that guide the insect to the nectar.) I used a bluebell.
Butterfly - attracted to bright coloured flower with an odour. The flowers are often wide, so the butterfly can land on it, but the butterfly can also fit its proboscis into a tubular flower. Butterflies use patterns or nectar guides to find the pollen. I used a marigold.
Fly - attracted to white/green/yellow/brown coloured flowers, often with funky/putrid odour (not sweet). Flies have a short tongue, so need a bowl-shaped flower. I used a buttercup (bees and beetles also pollinate buttercups).
Humming bird - red/yellow/orange coloured, odourless, tubes/funnels/cups. I used honeysuckle.
Beetle - white or green coloured, odour can be absent or strongly fruity, large bowl shape to crawl into. I used a dogwood flower.
Moth - dull red/purple/pink/white coloured, strong sweet smell emitted at night, various shapes.

Give students one image card with a pollinator image on it. Ask them to post it in the correct tub, before coming back for another one.
Students keep posting until the picture squares run out.

Water cycle posting game
Arrange the pots in a large circle, in the order of the water cycle events (evaporation - water vapour - condensation - clouds - precipitation - runoff).
If it is wet outdoors the water cycle words to post should be laminated.

Plant classification posting game
Place the pots next to the same plant as on the image.

Life cycle posting game
Pots display different kinds of animals, for example: fish, bird, reptile, amphibian, mammal, insect, crustacean.
Cards display different stages of life cycles, for example: egg, live birth, juvenile, larva, nymph, pupa, adult.
Students post a life cycle stage in a pot who's animal has that stage. There will be more than one pot in several cases. Challenge students to find a different pot if they get the same card again.
Once the cards are used, dump out each pot and arrange the (correct) cards in a circle (over images if possible) to show the life cycle of that animal, filling in any gaps with extra cards. Move the incorrect cards to the correct animal life cycle, without dwelling on the mistake.

Hand out magnifiers and practice using them by looking at fingerprints. Take time to make sure every student is using it correctly.

Tip the cocoons out of their box and place on students' desks, so that they can look at them closely.
Before half an hour is up, return the cocoons to their box, and take outside to place in the installed mason bee house. (If the cocoons warm up for too long, bees may start emerging!) Students might hear the bees moving around inside.

Explain how the bees will hatch within a couple of weeks (the males first). They feed on flower nectar near to where they hatch. Then they will mate, and the females will lay eggs in the tubes of the house. Over the following months, into the Fall, the eggs will hatch, a larva will grow, and eventually make a cocoon to protect it through the winter. The adult bees will hatch out next early Spring. (Cocoons that have been harvested and sold are kept at fridge temperature, so that the bees do not emerge until the cocoons are placed outside.)