One of the difficulties with teaching science to children is that, in every scientific field, the breadth and depth of knowledge is vast and our understanding of the fundamental principles of each field is complex and nuanced. We often try to teach our children by finding the fundamental basis, like the cell in biology or the gene in evolution, and work up from there. However, that can often confuse kids. It is often best to teach a subject in the same order than humanity learned it over time. For example, if you are teaching evolution, you will talk about how there are so many different breeds of dogs and about how there are so many different types of birds, including eagles, and so many different sub-types, like bald eagles. If you were to teach your child biology, you would talk about the parts of the body and how they work. You might skip dissecting cadavers and instead use software and picture books to show your kid what muscles and bones look like. After you establish what the body does on a macro level, you could get a microscope and show your kid what skin cells look like on the micro level.
Chemistry is much like evolution, in that people had been using it before they understood what it was fundamentally. Making beer and bread are essentially acts of chemistry, and they’ve been around for some ten thousand years. Metallurgy is also applied chemistry. When we start teaching our kids about chemistry, we don’t need to jump right in to atomic bonds and quantum physics. We can start the way humanity started: by mixing various substances and seeing what happens.
When introducing a new concept to kids, it is often important to start with any relevant vocabulary. You can’t talk about a subject if you don’t know any of the words that describe that subject. The best place to start is with the forms of matter: liquid, solid, and gas. (You can skip plasma and Bose-Einstein condensate if your kid is younger than 6.)
You can make a chart for your kid, which simply looks like this:
Have your kid add more ideas to the chart. Talk to your kid about how ice, water, and steam are all different forms of water. You can give your kid an ice cube and have them see how it melts into water and sublimates into steam. You can also boil some water and watch as the water turn to steam. Ask your kid what liquid rock or metal might look like. You can talk about volcanoes and metal smithy so that they know that different substances have different melting and boiling points.
When I was a kid I kept asking my mom what form of matter fire was. She kept saying that it was a chemical reaction, and not actually matter. I could not wrap my brain around that as a kid. You may find your kid throwing words at you like fire, or the sun, or Jello, which don’t fit neatly into the chart. You could, if need be, add a fourth column labeled other, and tell your kid that, over time, you will learn about the items on that list.
Two other important words are react and transform. For the purposes of a six year old, react means that something happens when you put two different substances together. There could be heat, light, a change of color, or a smell. Transform means that one or more of the substances changes its state, or the two substances mix together and become something new. There are two experiments you can do with your kid to show reaction and transformation.
The iconic kitchen science experiment is the volcano made of vinegar and baking soda. This is an excellent way to show your child how two inert substances can be mixed to cause a violent, or at least entertaining, reaction. For this experiment all you need are: water, a 20 ounce drink bottle, a deep pan, dishwasher detergent, baking soda, and vinegar.
Step 1 Fill the bottle three quarters full with hot water.
Step 2 Add half a teaspoon of dish detergent and two tablespoons of baking soda. Have your kid stir the mixture until it is uniform. You can use this time to teach your kid the word solution, which basically means a stable mixture of different chemicals.
Step 3 Put your bottle in the middle of the pan. Ask your kid what they think will happen when you add the vinegar to the liquid mixture. Have them list a series of hypotheses: maybe nothing will happen, maybe the color will change, maybe there will be a smell.
Step 4 Have your kid pour the vinegar into the mix and watch as the liquids combine and create a geyser of bubbles. You can keep adding baking soda and vinegar to continue the eruption.
What your child has observed is a transformation: Baking soda, (sodium bicarbonate) and vinegar (acetic acid) combine to form carbon dioxide, water, sodium and acetate. Carbon dioxide is a gas, so it produces bubbles in the mixture. It is the same gas that you find in soda. Chemicals from one mixture separate and combine with chemicals from the other mixture, causing a variety of new substances to form. Much like mixing red and yellow to make orange, mixing a substance that is carbon and X with a substance that is oxygen and Y creates carbon dioxide and XY.
An excellent experiment for showing reaction is cleaning pennies with vinegar and salt. Start by collecting a bunch of old pennies. Ask your kid why old pennies are dirty and dull, while new pennies are shiny and bright. The answer is, in part, because they’ve been handled by thousands of people, all of whom excrete grease and leave it on everything they touch, and the pennies have accumulated decades of human oil, making them about as gross as a touch screen. However, there is another reason why they are green and dingy which is way less disgusting.
In a bowl, mix a quarter cup vinegar with a teaspoon of salt. Have your kid hold a penny, dip it in the solution halfway, and hold it for thirty seconds. When they pulls it out, there will be a neat line across the middle, under which the penny is clean and above which it is dingy. What they’re seeing is a reaction: the copper oxide on the surface of the penny is being dissolved by the vinegar (acetic acid). The reason the pennies were greenish to begin with was that the copper on their surfaces reacted with oxygen in the air to create a film of copper oxide on the outside of the penny. This process simply removes that film.
Dump a bunch of pennies into the solution and watch as they react, becoming cleaner before your eyes. Pull them out after five minutes. You can put half of them on a paper towel to dry, and then rinse half of them in water and leave them out to dry separately. After an hour check back to see if there is any difference between the two groups. The rinsed pennies will look just as they did when you pulled them out of the solution. However, the unrinsed pennies will again be turning green. This is because the residue on the pennies precipitates a reaction between the copper and the oxygen in the air, again putting a film of copper oxide onto the pennies.
This is a great way to introduce the idea that chemicals are all around us, and are constantly interacting. The air is made of a variety of chemicals, and they can react with solids and liquids. For example, you can talk to your kids about what rust is, or how the air they breath in is different from the air they breath out.
Without knowing that a chemical is made of a variety of molecules, which are made of atoms, which interact by means of different bonds, your kid can see how chemistry works, and begin to understand that matter is made not of immutable substances, by of combinations of substances that can interact, degrade, transform, and recombine to form other substances.
Soon you will be introducing your kid to the periodic table of the elements, where they will likely be drawn towards unununium, or Uuu, element 111.