ingridscience

While the popcorn is popping, talk about what is happening to make this food:

Each kernel has some water in it. (Corn that is used for popcorn has just the right amount of water: 13.5%.) As the hot oil heats up the kernal, the water inside it evaporates to form a gas (water vapour). The shell is strong and watertight so the gas cannot escape.
As the heat increases further, the water vapour molecules move around more and more vigorously, exerting more and more pressure on the inside of the shell. Eventually the pressure inside the kernel is great enough to burst the shell. (This happens at about 180 centigrade, when the pressure inside is 135psi.)
As the shell bursts the pressure suddenly drops again. This causes the water vapour to expand which makes the starch and proteins inside the kernel expand into an airy foam.

Students can inspect the kernels as they eat them, and see that the shell turns inside out from the force of the explosion.

If students have done some acting out the sates of matter already, they can do skits in small groups on what is happening inside the popcorn to make it pop - each student can be a water molecule, or the kernel shell, or a narrator. Gather to view each others' skits.
(Students can prepare their skits as the popcorn pops if it takes a while.)

Show students slow motion videos of popcorn kernel popping (maybe while they eat their popcorn):
https://www.youtube.com/watch?v=CXDstfD9eJ0
https://www.youtube.com/watch?v=NCSr18vtjeo

more popcorn info at: https://www.popcorn.org/Facts-Fun/What-Makes-Popcorn-Pop
Make popcorn with a microwave and paper bag; https://www.allrecipes.com/recipe/87305/microwave-popcorn/

For a lesson on heat:
Popcorn can be made as part of a lesson on heat. Students brainstorm whether the popcorn is being popped as a result of conduction, convection, radiation or all of them.

For a lesson on seeds:
Compare popcorn kernels with the kernels on a corn cob.

Teach students how to make a basic paper airplane. If they know already, let them fold their way and start testing immediately. Make sure students make the creases tight and neat as they can.

(Plane design ideas with step by step instructions at many websites, including https://www.exploratorium.edu/exploring/paper/airplanes.html and https://icdn.kiwico.com/landing/at-home/2020_04-Kids-at-home-Printables…)

Forces on an airplane
Ask students to think about the forces on their planes as they fly them. Students can alter their models now if they want, but for now, the emphasis should be on watching them fly and thinking about the forces involved.

After a while, stop the flying action, gather as a group and discuss what forces they think keep the plane in the air. Introduce terms and round out the concepts as appropriate for the grade level:
1. Thrust is the forward force on an airplane. Your arm muscles throwing the paper airplane generate initial thrust which send the paper airplane forward. (In a real airplane, thrust is from a propellor or jet engine and is continually acting as the plane flies.)
2. Drag is the force that slows the plane down as it pushes against the air it is moving through. It is a kind of friction and is also called called air resistance. It acts in the opposite direction from thrust. Thrust must be equal to or greater than drag for a plane to move forward, hence your paper airplane slows down as the energy from the initial thrust is used up. The more streamlined an object is, the less drag it has. (Airliners retract their landing gear between take off and landing to reduce drag on the landing gear which would otherwise rip it off.)
3. Gravity is the force pulling the plane downwards. It acts on the mass of the plane, giving it weight.
4. Lift is the force that pushes the airplane up, acting in the opposite direction of gravity. Lift is produced by the wings and the air flowing around them (either the wing or the air must be moving - they just need to move relative to each other).
The tilt of the airplane and the angle of the wing means that air flowing off the wing flows downwards. This downwards force pushes back up against the wing, and lifts the wing (because of Newton's 3rd Law of action and reaction). (The Bernoulli effect has previously been used to explain lift, but is now known to be insignificant, or even incorrect - it doesn't explain how a plane can fly upside down.)

Depending on the strength of each of these forces, the plane will fly forwards, downwards, upwards or stop.

As an aside, drag and lift can be felt with a hand out of a car window:
Holding your palm flat against the wind you can feel the air pushing against it: drag, or air resistance. If you make a fist, your hand is smaller and there should be less drag on it.
If you hold your flat hand straight out of the window, then slowly tip it so the front edge is tipped up a bit, the air is directed downwards and pushes your hand up. The effect is quite dramatic and nicely demonstrates action and reaction.

Continuing the lesson, ask students how they might make their plane go further. Ideas following.
More thrust by throwing more strongly (they are probably doing this anyway).
More streamlined to reduce drag (change how it is folded so it has a narrower front),.
More lift by changing the angle of attack (point it upwards to start). To tip the nose of the airplane upwards during flight (and keep the angle of attack optimal), bend up the back of the wings a little (see photo). A little bend goes a long way. Air flowing off this bend will push the back of the airplane down, which will lift the nose.
If the nose rises upwards and then the plane drops, the plane is stalling. Bend the back of the wing downwards, to make more air flow downwards off the back of the wing and lift it, so tipping the nose downwards - now the nose does not rise so fast and the plane will not stall. Keep your adjustments small.
You may also want to discuss adding other folds, such as winglets, to their plane. Winglets are additional upwards folds on the end of the wing, and reduce a vortex of air that pushes the wing down.
Flaps cut into the back edge of the wing can also increase lift, or be bent in opposite directions to make the plane spin.

Encourage students to share designs and tips on how to throw their plane, and allow more time for testing.
They can measure and record how far their plane goes. Generate a class graph of the distances achieved, and discuss factors that might increase flying distance.

Airplanes modelling how birds change direction
Fly an airplane to see how long it stays aloft.
Then bend up the back of the wings a little (see photo) - it should stay aloft a little longer.
Then bend the back of the wings down - the plane should dive to the ground soon after launch.
Try bending one up and one down (see photo) - at least one of the planes will roll as it flies.
Birds move their feathers on their wings, to change the direction of their flight.

Airplanes modelling bird wing shapes
Build differently-shaped airplanes, to model how some birds have wide wings for gliding, and others have swept back wings for fast flying. See this link for designs: https://www.audubon.org/news/these-paper-airplanes-fly-birds See the paper raptor designs from this link: http://idahoptv.org/sciencetrek/topics/birds_of_prey/activity3.cfm
Some birds of prey have swept back wings, so that they can dive at high speeds and catch other birds (e.g. peregrine falcon).
Some birds have long, wide wings to help them glide and look for prey e.g. hawks, eagles. They can open their wing feathers at the ends to keep the airflow around the wingtips smooth and to prevent stalling at low speeds.
Some birds have short broad wings and long tails to allow tight manoeuvring and quick takeoffs e.g. woodland hawks. However, they need to flap a lot.

Newton's Laws in a paper airplane
First Law - objects will stay stopped or in constant motion until a force acts on them (the force of your hand makes the plane go forward, the force of gravity points it to the ground)
Second Law - F=ma: for a constant force a smaller mass will accelerate more than a larger mass; a greater force will make the same mass accelerate more (a greater push from your hand will make the plane go further)
Third Law - for every action there is an equal and opposite reaction; when an object pushes on another it gets pushed back with equal force (your hand pushes on the plane and the plane pushes back on your hand, sending it forwards)

Before the lesson, find some good habitats for decomposers e.g.under logs and dead leaves, then take the students to these sites.

Students hunt for anything living in the soil. As they look more closely they will notice smaller and smaller animals. e.g. worms, wood bugs, slugs, snails. Also fungi and bacteria.

Discuss with the students what these animals eat, and that many of them have an important role as decomposers - living things that eat dead plant and animal matter. They break down living things into simple molecules that can be then used by plants (carbon compounds to CO2; nitrogen cpds to nitrite, nitrate and N2; phosphorus cpds to phosphate).
Decomposers often prefer it moist, dark and damp, where the rotting process is fastest.

Optional: study the animals more closely with magnifiers on site.
Optional: collect a few animals in soil to take back to the classroom, study more closely and make a food web.
Optional: collect worms or wood bugs to keep in a habitat in the classroom. Or release worms or wood bugs that have been in the classroom for a while.

Return any animals that do not have a habitat in the classroom to their collection site.

This is the last activity of the Honey Mystery.

Students compare the "fingerprints" of the left paw of each cat (as the investigators determined that someone picked up the honey jar with their left hand). See the worksheet.
Identify whether each print is an arch, loop or whorl.

Then look at the prints found on the honey jar (this can be given as a separate piece of paper to stick onto the worksheet).
identify which cat made the prints on the jar.

For our case, it was the black cat that stole the honey.

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.

Before the lesson, write the note using one of the black pens. Example of what it can read: "What you seek is buried under the old cedar at the back of the house". Something more applicable to the classroom or school building would be better.

In the lesson, read the note to the students, and show them the black pens that might have written the note, and that they will use chromatography to figure out which one. Demonstrate the steps below, before allowing them to proceed.

Prepare chromatography strips for the black pens:
Cut out filter paper, using the template to make the correct size. Draw a pencil line across the paper, where indicated on the template (see 1st photo).
With each black pen make a line across the strip of the filter paper, over the pencil line.

Prepare chromatography strip for the ink on the note:
Cut off a small piece of the note with a word on it, lay it word-side down on a filter paper strip, at the same level as the line on the template, and use a paperclip to attach them together. (2nd photo.)

Run the chromatograms:
Clip the top of the filter paper strips with the small binder clips (for all the black candidate pens, and for the note). Then thread the coffee stir stick through the binder clip arms and lay the sticks across the top of the tub. The filter paper should dip into the water, but the black lines and the piece of note are above the water line. Allow the chromatograms of the three candidate pens to run (3rd photo). Wait three our four minutes until the colours have separated up the filter paper to within 1cm from the binder clip.
Although the chromatogram with the note is not as distinct as the chromatograms from the black lines, the colours should still be distinguishable, so that the pen that wrote the note can be identified (see 4th photo comparing the chromatogram from a line and from a note).

Many black pens have a different chromatography pattern (see 5th image). Note that marker brands change their ink composition now and again (e.g. crayola now has more ink colours in some of their black markers).

How does chromatography work?
The coloured dye molecules in the ink of the pen are attracted to both the water that it is in, but also the surface of the filter paper. Each different colour is attracted to the water or the filter paper to different extents. As the water moves up, the dye molecules that are most attracted to the water will move along fast with it. If the dye molecules are mostly attracted to the paper, they will get stuck to the paper and not move along with the water at all. Most colours are attracted to both the water and the paper, so will travel with the water for a while, then stick to the paper for a while. Depending on the relative attraction of a dye to the water and the paper, a colour will travel at its own rate. The differing rates of travel separate out the colours.

Students view human and animal hairs with magnifiers and ideally a microscope. They can tape them to a worksheet, piece of paper or microscope slide to make viewing easier. They should notice different colours and widths. Under the transmission microscope the pattern of scales on the surface of the hair will also vary.

For a lesson on animal hair function:
Look at the different thicknesses of hair and discuss their purpose. Dense, fine underfur (for warmth) and the long, coarse guard hairs (for protection against the weather and dirt, to raise when confronting other animals.

For a lesson on forensics:
Discuss how hairs are quite different from each other. They can often be used to determine the race of the person they came from, and also whether the hair was dyed. Hair also contains chemicals that have been ingested, so can be tested for drugs or other chemicals.
Students can have an array of hairs in little baggies, and guess their source e.g. cat hair may have identifiable colours distinct from human hair.

Optional: Give students other kinds of "trace evidence" each in their own baggie, for students to try and identify, to mimic a crime scene investigation e.g. paint flakes, wood splinter, carpet hairs.

Forensic scientists may find hair with a root attached - you can pull out a hair from your head forcibly to see the root (a tiny white blob). The root contains hair cells, which can be used to extract DNA and identify a person involved in a crime.