# Classroom demonstrations for younger students

#### BryceUnderwood

I'm a senior in high school taking AP Physics II, and I was recently elected as the president of my schools Science Club. Our first thing to do is to go to the local elementary schools and give interesting physics demonstrations to the younger students grades K-6. I really enjoy space and I know many children like that too, so I was planning on taking volunteers to be "Planets" and line them to scale to show how far the planets are in comparison to the earth. I was just wondering if there are any other interesting demonstrations for younger children that have to do with space, motion, forces, or anything that they will maybe understand somewhat easily. Thanks!

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#### fresh_42

Mentor
2018 Award
Those funnels in which you can roll in a coin to demonstrate gravity. (Or a mat made of rubber with a bowling ball on it.)
A candle (at night or in the dark) at different distances to demonstrate the change in luminosity.
Let someone juggle balls and throw a heavier one into his play to catch it: demonstrates how heavy objects (nemesis?) can destroy planetary systems.
Throwing pebbles (or other objects) into a sand pit (let them do their best to achieve high velocities!) to demonstrate craters or throwing them on a target far away to demonstrate how rare it is to get a hit.
Destroying balls of plaster to demonstrate impacts.
Kepler's laws with an elastic band.
2 Kids moving 5 yards left: one at a distance of let's say 10 yards and one at 100 yards to get a feeling of fix stars, distances resp.

#### vela

Staff Emeritus
Homework Helper
I'm a senior in high school taking AP Physics II, and I was recently elected as the president of my schools Science Club. Our first thing to do is to go to the local elementary schools and give interesting physics demonstrations to the younger students grades K-6. I really enjoy space and I know many children like that too, so I was planning on taking volunteers to be "Planets" and line them to scale to show how far the planets are in comparison to the earth. I was just wondering if there are any other interesting demonstrations for younger children that have to do with space, motion, forces, or anything that they will maybe understand somewhat easily. Thanks!
Make cards with small circles drawn on them to scale to indicate the actual size of the planets. This will reinforce how tiny the planets are compared to the size of the solar system. You could also add a speed-of-light aspect to this. Have one of the kids start at the Sun and walk toward the planets at the correct rate. Even though the speed of light is very fast compared to our everyday experience, it's pretty slow when you see it in comparison to the scale of the solar system and universe.

Mixing corn starch and water is an easy demonstration of a non-Newtonian fluid. Have the kids try make the mixture and experience how it quickly becomes very difficult to stir. Also, when they jab the surface with a finger, it'll feel solid, but if they gently press, their finger will readily sink in.

If you prepare mixtures of salt water with different salinity and colors, you can layer them on top of each other, showing how the density changes with salt concentration.

If you have a little money to spend, get the Static Electricity Science Kit with a Fun Fly Stick. It has a number of fun and easy demos.

Tie-dyed milk is another fun one. You put a few drops of food coloring on whole milk, and then add some dish washing soap. (You should definitely try this one on your own first to find out what techniques and soap work best.)

YouTube is actually a good source for demonstration ideas.

#### Mister T

Gold Member
The key to success is having the right equipment. Do you have access to a portable vacuum pump and liquid nitrogen? There's a lot you can do that will fascinate children of all ages.

#### berkeman

Mentor
The key to success is having the right equipment. Do you have access to a portable vacuum pump and liquid nitrogen? There's a lot you can do that will fascinate children of all ages.
You're going to wheel a liquid nitrogen Dewar into an elementary school? Why not just show them some YouTube videos instead -- would be a lot safer, IMO...

#### Mister T

Gold Member
You're going to wheel a liquid nitrogen Dewar into an elementary school?
A 20-liter Dewar flask, yes. I've done it many times. I also ignite a soup-can cannon that uses a lighter fluid explosion to propel a tennis ball. Also use a sledge hammer to break a cinder block on the chest of a student lying on a bed of nails.

Why not just show them some YouTube videos instead -- would be a lot safer, IMO...
Safer, yes. Anywhere near as effective, no. The day they make me do that is the day I stop. I am always amazed by the fact that no one questions my professional capacity to do this safely.

#### fresh_42

Mentor
2018 Award
A 20-liter Dewar flask, yes. I've done it many times. I also ignite a soup-can cannon that uses a lighter fluid explosion to propel a tennis ball. Also use a sledge hammer to break a cinder block on the chest of a student lying on a bed of nails.
This reminds me on my chemistry courses at school. We heard about how to fish with potassium, how to distill alcohol in harsh times, learned that a chemist who got caught killing his wife has missed his profession, that cats don't drink alcohol unless you frustrate them and so on. Funny stuff, however, my knowledge on chemistry itself is rather poor.

#### berkeman

Mentor
A 20-liter Dewar flask, yes. I've done it many times. I also ignite a soup-can cannon that uses a lighter fluid explosion to propel a tennis ball. Also use a sledge hammer to break a cinder block on the chest of a student lying on a bed of nails.

Safer, yes. Anywhere near as effective, no. The day they make me do that is the day I stop. I am always amazed by the fact that no one questions my professional capacity to do this safely.
Do you want me to feel comfortable about your advice for elementary school student demonstrations? You are falling short of making that case so far, IMO...

#### berkeman

Mentor
From your Profile, it looks like you are an instructor at a community college. Can you comment on what the differences might be between demonstrations for community college physics students (great stuff, BTW), and elementary school students?

#### symbolipoint

Homework Helper
Gold Member
Elementary school students should not be allowed to handle nor to get too close to liquid nitrogen, and the high school students performing their demonstrations with this need to be properly trained for handling such materials and associated equipment, and if these high school students are not yet significantly over the age of 18, they may need to be supervised by one or more adults who have the necessary technical knowledge and training.

#### Mister T

Gold Member
From your Profile, it looks like you are an instructor at a community college. Can you comment on what the differences might be between demonstrations for community college physics students (great stuff, BTW), and elementary school students?
Thanks. The demonstration show (and it is a show) works best for people in about 5th grade, although it's definitely a big hit for people of every age. The intent here is to spark interest in science and have some fun learning some science.

For college students enrolled in a physics class I don't do the entire show. They will see some of the demonstrations at appropriate points in the course. The intent here is to teach them the stuff in the curriculum, and if they can have some fun doing it all the better, but it's of secondary importance.

#### Mister T

Gold Member
Elementary school students should not be allowed to handle nor to get too close to liquid nitrogen, and the high school students performing their demonstrations with this need to be properly trained for handling such materials and associated equipment, and if these high school students are not yet significantly over the age of 18, they may need to be supervised by one or more adults who have the necessary technical knowledge and training.
I agree that the demonstrators would have to be old enough, responsible enough, trained, and possibly supervised. I would limit the demonstrations to the ones that are more safe.

#### brainpushups

Tie-dyed milk is another fun one. You put a few drops of food coloring on whole milk, and then add some dish washing soap. (You should definitely try this one on your own first to find out what techniques and soap work best.)
This is a good one and there's lots of room for explanation: surface tension and surfactants are the clear connection, but you could also use it as a vehicle to discuss entropy and the heat death of the universe.

One cheap and effective demonstration/activity would be to have the students make an electrophorus. You need some styrofoam blocks, small pieces of silk cloth, some pie plates, and glue (hot glue is nice because it works quickly, but may not be appropriate for the younger group of kids).

If you have access to a Van de Graff generator then there are at least a dozen demonstrations that you can easily look up.

Optics is also a good place to go. There are plenty of simple and interesting reflection, refraction, dispersion, and diffraction activities/demonstrations. One cheap activity would be to make spectroscopes from toilet paper tubes and CDs (for the diffraction grating - strip off the reflective part of the CD). You can find plans easily online. Optical illusions are also fun. There are many demonstrations about color and color mixing you can also readily find.

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