There’s an updated version of this post here: https://inventorsoftomorrow.com/2016/12/14/chemistry-for-kids-mixtures/
This week’s class was about a fundamental concept from chemistry: when you mix two things together, sometimes they combine, sometimes they stay separate. (At this age, we don’t get into the details of electrons, molecular bonds, and so on! We just want them to experience it now, and someday when they do get all the details, it will make much more sense to them than kids with limited hands-on experience.)
Question of the Week: Will all things combine when mixed together?
In this blog post, I’ll just tell you what we did. To learn about the science, you can check out the posters I made to hang in class which explains the science behind how each of these experiments work. (Here’s the pdf)
Concept exploration – Milk Fireworks: Take a flat shallow dish, pour in a thin layer of whole milk (not skim – you need the fat!). Drop on a few drops of different food colors, near to each other – they mostly float on the surface of the milk, since the water-based colors are less dense than the milk. Dip a q-tip into dishwashing detergent (Dawn and Joy work best), then dip it in the milk near the coloring and hold it there, but do not stir!! Wait a second for the response – the colors fly away from the q-tip. (This photo from Steve Spangler Science shows an effect you may see – you can also do an image search for “milk fireworks” to see lots more!) Once the reaction slows down, you can gently stir the milk and the colors will swirl around, creating a marbled effect.
This is a great experiment! Pretty cheap, easy to clean up, entertaining for all ages. The challenge we found was convincing our three year olds and four year olds to put the q-tip in and hold it there waiting for the reaction. They just want to stir. The colors still move and intermingle, but it’s not as dramatic or pretty.
Oil and Water:
Demo this in circle first (see below), then let them explore it on their own. Place out plastic containers (We used plastic Test Tubes), pitcher of water, jar of oil, water-based food coloring and oil-based food coloring*. They can try a variety of combinations. Here’s an article about this experiment: http://www.metrofamilymagazine.com/May-2012/Simple-Science-Experiment-Oil-Water-and-Food-Coloring/
For the oil coloring, I used Americolor Oil Food Coloring but I want to try other brands, because this color mixed with both the oil and the water, so I didn’t get quite the color separation I wanted. I was hoping for blue water and yellow oil where you could then shake them together to temporarily make green that would then separate out again. Instead I had green water and yellow oil.
Another way to explore this, from The Curious Kid’s Science Book, is to fill a shallow tray with oil. Give your child containers of colored water and a pipette. They can drip in bits of water and watch them ball up. Try this in a clear container on a light table – if you think your kids are up to doing it without spilling – otherwise, put the clear container on white paper so the colors are obvious.
Fireworks in a Jar: Another experiment we didn’t try was to fill a jar most of the way with water, then in a separate container, whisk together oil and food coloring. Pour the oil on top of the water – the food coloring will gradually separate out, sink through the oil, and cascade into the water then mix with the water. Do a google search for “fireworks in a jar” to see lots of examples, including I Can Teach My Child.
Chromatography – What color is that black marker? Supplies: strips of paper towel, various watercolor black markers and small container of water. Choose a marker and draw a line 1 – 2 inches from the end of a paper strip. Dip the very end of the strip (below the line) into the water, and lay the rest of it out on the tray. It wicks up the water, bringing the color along with it. With SOME markers, unexpected colors separate out. Learn more: www.crayola.com/crafts/marker-chromatography-craft/ and http://b-inspiredmama.com/marker-chromatography-science-experiment/ www.exploratorium.edu/science_explorer/black_magic.html
Sharpie tie-dye: Supplies: coffee filters, permanent markers, rubbing alcohol (90%) and pipettes or eye droppers. Kids draw on the coffee filter, then drip on a little rubbing alcohol and watch the colors spread. You can tie-dye shirts this way if desired.
www.youtube.com/watch?v=tg8g2mk2fsY This experiment didn’t attract a lot of interest… we have done other experiments recently with dripping liquid watercolors onto coffee filters, and this may have felt too similar.
Crystals Painting: You could also do Epsom salt painting this week if you didn’t do it with States of Matter.
Water Table: I soaked water beads the night before (polymers) and put some in the water table with fishing nets (our Tool of the Week) and scoops. I had two brands of water beads – I can’t remember what brand the blue ones are – I’ve used them over and over. The multi-color beads were bio-gels. At the end of the day, the blue ones were whole and ready to be dried and re-used. The multi-coloreds had been squished into lots of little bits of loose jelly we had to fish our of the water. So, test your beads ahead of time!
Building Toy: ZOOB are a fun building toy which require learning a new small motor skill for many kids – knowing how to line it up just right and push hard to connect them. They only hook together in certain ways – can form matrices – kind of like molecule models.
Bubble wands. The kids used pipe cleaners and beads to make bubble wands for outside time. http://www.prekinders.com/bubble-chemistry/
Snack: A great snack would be to make either a cake or pancakes to go with the cake recipe song or the pancakes book that we did in circle time.
Beverage at Snack Time: Koolaid or other powdered drink mix you stir into water – talk about how the powder dissolves in the water, and then mixes in.
Large motor: This day is a lot of high concentration, small motor, try not to make too much of a mess activities. The kids need to be able to blow off physical steam. So, we had tumbling mats in the big motor room and had a long outside time to play.
Challenge Activity # 1: Can you make a bouncy ball?
We followed the directions on chemistry.about.com. (They credit their source as Meg A. Mole’s Bouncing Ball.) The notes in brackets are from our observations.
- Pour 2 tablespoons warm water and 1/2 teaspoon borax powder into the cup labeled ‘Borax Solution’. Stir the mixture to dissolve the borax. [The water needs to be very warm, and you need to stir a while to be sure it’s all dissolved.]
- Pour 1 tablespoon of glue into cup labeled ‘Ball Mixture’. Add food coloring. [The website recommends blue or clear school glue – we weren’t able to find that, so we used Glitter Glue. The balls turned out a pale shade of the glue color, with subtle hints of glitter. We did test a couple with multi-purpose glue and food color.]
- Add 1/2 teaspoon of the borax solution you just made and 1 tablespoon of cornstarch. Do not stir. [Tip: this works best if you use a wide dish where the glue spreads out a bit – sprinkle the borax solution around over all the glue, then sprinkle the corn starch all over that. If you just dump the solution in one place, you’ll end up with part of the mixture interacting great and turning into a ball and other parts where the reaction never really happens, and the ball just won’t form correctly. We learned to use a paper/cardboard snack tray to mix in as cleaning up a dish after making these takes a LOT of scrubbing – easier to throw away a snack tray.]
- Allow ingredients to interact on their own for 15 seconds (the video on about.com says 15 minutes, but it’s really seconds), then stir them together to fully mix. Once the mixture becomes impossible to stir, take it out of the cup.
- Knead the ball by rolling it around in your palms. It’s VERY sticky at first. [As you keep rolling it, you’ll feel it start to pull together into a ball. If it’s still really sticky, sprinkle a little more corn starch onto it and keep rolling.]
- Once it’s solidified, bounce it.
- When you’re done playing with it, put it in a Baggie – write name on the baggie!
So, when I tested this before class, it worked perfectly. Ridiculously easy, made a nice ball. Not commercial quality or anything, but enough to feel like a very successful experiment. But, then at the end of the first class, our record was 3 successes, 6 failures. And the photo above was one of our “successes.” It bounced, but it wasn’t beautiful. We got better as we figured out the tips above – the afternoon class had about an 80% success rate. Good enough to be worth doing as an activity, but not as good as hoped.
Kids’ Activities Blog recommends using just 1/2 tablespoon of cornstarch and mixing glue, cornstarch, and food color together before adding borax solution. We’ll test that next time.
Challenge Activity #2: Make your own silly putty.
Sources I used for ideas: http://www.sciencekids.co.nz/experiments/crazyputty.html http://www.wikihow.com/Make-Silly-Putty http://www.pbs.org/parents/crafts-for-kids/homemade-silly-putty/.
Supplies: Elmer’s Multi-Purpose Glue (apparently Elmer’s school glue does not work); food coloring, liquid starch (Sta-Flo – apparently Niagara doesn’t work); tablespoon, spoon, dish to mix in, plastic eggs.
- Put two tablespoons of glue in a dish.
- Add food coloring. Mix.
- Add one tablespoon liquid starch. Stir.
- Let sit for five minutes.
- Knead for five to ten minutes.
Note: The recipes I saw often recommend one part glue and one part liquid starch. That led to a handful of liquidy goo that was not kneadable. I added a bunch more glue to my hand and kneaded that in. So, I recommend you start with two tablespoons. When you first start working with this, it’s goo. It takes several minutes of kneading to turn into silly putty. But, in the end, it was a pretty satisfying imitation of silly putty.
But… we decided not to use this in class. Having to wait five minutes mid-process, then having to knead for 10 – 15 was too much to ask our little kids. Plus, the recipe results in silly putty, and many parents can tell you awful stories of silly putty in their carpet or upholstery, and we decided not to send our families home with a product they’d later resent us for.
Make bubbles: You could make your own bubbles. There’s fun science in understanding that although water and soap make bubbles, to make long-lasting bubbles, you need some sort of sugar. Here’s one recipe: Measure 3 cups of water into one container. Add 1/2 cup dish soap, and stir GENTLY. Add 1/2 tablespoon glycerin OR 2 tablespoons light corn syrup. Stir gently. You can use it right away, but it works even better the next day.
How to communicate the answer to the key “Question of the Week”? I asked “When you mix things together, do they always combine into one new thing or do they stay separate? Let me show you an experiment, and we’ll see.”
I started with a demo of oil and water. I poured water into a test tube, then showed them the regular food coloring Food Coloring, and explained it was color chemicals mixed with water. So, we know it will mix with water. I put a few drops in the water and mixed it.
Then I showed them the oil and explained that water and oil do not like to combine. I reminded them the regular food coloring was made of water, and added a few drops to the oil. It beaded up, and I put the lid on the oil, and showed how I could pour the oil back and forth in the tube, and the ball of food coloring would not mix in. Then I poured some water in with the oil, and shook it gently to mix it, then showed how it separated out again, with the oil floating on top of the water. I also added the Oil Food Color to the oil to show how it could mix in because it was color mixed with a chemical that “likes” to connect to oil.
Matter and molecules. I reminded them about what matter and molecules are. We covered this in states of matter class. I used red ZOOB and said “imagine these are iron molecules. They like to connect to other iron molecules. They can also mix with other molecules, like copper” (I add a green ZOOB), “and silver” (I add a gray ZOOB) “and gold” (a yellow ZOOB.) [Note: I have not validated the scientific accuracy of these chemical bonds… I’m teaching preschoolers, so I just need big picture to be right, and don’t guarantee all the details. Feel free to correct me in the comments with another suggestion for examples ot use… 🙂 ]
Then I held up two mega-blocks of one color and said this was another kind of chemical – hydrogen – and it hooks up really well with other hydrogen. And it can hook up with some other chemicals like oxygen – I pull out a duplo and show how even though it’s different from the mega blocks, they can connect.
But then I showed that the mega-blocks and Duplos will not connect to the ZOOB no matter how hard we try. This is similar to how water and oil won’t connect.
Book: I didn’t find any little kids’ books about chemistry (I did find books for adults and older kids about chemistry experiments to do, but nothing with a story.) So we read a book tied to last week’s Egg theme. You could also read a book about cooking such as Whopper Cake, which would tie in nicely with the song we did…
Song: We used the Cake Recipe song. (I explained how when we cook food from a recipe, we’re basically doing chemistry. And that you had to follow the recipe right, because flour, eggs, milk, and sugar can make cake, but it can also make bread, all depending on how you mix it together.)
Before teaching the song, I had them clap the rhythms of the chorus: 1-2-3 1-2-3 mix-mix-mix mix-mix-mix and 1 2 3 4 mix mix mix mix. Rhythm is an important building block for the brain, helping with later math learning and more.
Book: We read Pancakes, Pancakes! by Eric Carle. Not only is this about the chemistry of cooking, but it also goes through how we get flour (harvesting, threshing, grinding – it showed a water wheel powered mill which allowed me to remind them about our Simple Machines unit on Wheels, and showed a water wheel like we use in the water table, but being used to create power before we understood electricity.
Songs: Handed out the egg shakers we made in egg science week, and sang the cake recipe song again, using shakers to mark the rhythm.
Cool ideas we didn’t try:
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