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Chemistry Unit ’ Category
Wednesday, November 21st, 2012
Isn’t this pretty? This was one of our experiments as we finished up our chemistry unit!
One of the chapters in our chemistry book (Real Science 4 Kids-pre-level 1) talked about mixtures. It talked first about how how some mixtures dissolve (like salt in water). Then it went on to talk about soap and soap molecules. We read how soap makes things like butter and grease “dissolve” in water. Detergent is attracted to both oil and water helping them join together.
We did a little experiment to show how soap helps get your dishes clean. We took a couple of baby food jars and put oil and colored water into each. Then to one of the jars we added dish detergent. We all watched as the detergent took its time and then slowly sank down through the layer of oil. We shook both jars vigorously and then set them to the side for 20 or 30 minutes.
When we came back, we could see that the jar without detergent had separated back into two layers — oil and water. In the other jar, the oil and water still seemed to be mixed together. The older kids learned that this is called an emulsion.
While we were waiting for the experiment above to finish we went on to another mesmerizing activity. We’ve done this before and it never fails to captivate us! All you need is milk in a bowl, food dye, detergent and a Q-tip. You place a few drops of dye into the milk, dip the Q-tip into detergent and then very gently place the Q-tip into the water. The colors start racing around. The kids then dipped their Q-tip into the detergent again and gently placed it back in the milk in a different spot. The colors start moving and swirling about. It’s really pretty to watch!
The action in this experiment is a bit complex. Our chemistry book showed how soap molecules have different properties. Our book explained it as one end being “oil-like” and the other, “water-like.” Oil dissolves in the oil-like ends of the soap and becomes surrounded by the water molecules. This experiment shows the movement of molecules as the fat molecules are interacting with the soap detergent molecules.
Steve Spangler explains this milk experiment this way, “The molecules of fat bend, roll, twist, and contort in all directions as the soap molecules race around to join up with the fat molecules. During all of this fat molecule gymnastics, the food coloring molecules are bumped and shoved everywhere, providing an easy way to observe all the invisible activity. As the soap becomes evenly mixed with the milk, the action slows down and eventually stops.”
Other sources explain that other factors are at work here such as breaking the surface tension of the liquid, etc. If your child is older you could discuss those other factors as well.
At any rate, it’s a colorful fun experiment to do with anyone from pre-K on up. Who doesn’t like watching colors swirl and whirl?!
Our final experiment didn’t really connect with our chemistry chapter, but was another fun, color experiment to do with the kids. We took skittles and dissolved them in water. (You can also use M&Ms) I had the kids guess whether the colors would mix or stay separate. The older kids, of course, remembered doing this a few years ago, but ED didn’t. We talked about how scientists “make predictions” and then perform experiments to see if their prediction was accurate.
Skittles (or M&Ms) have an edible dye that doesn’t dissolve in water. There was equal pressure from all sides as the dye moved towards one another so the colors stopped moving forward. I explained it to the kids as if we had our palms out and were both leaning a little bit toward each other.
Do you want to do other fun experiments with candy? Be sure to visit this great website, Candy Experiments written by Loralee, a mom of three. I visited the booth they had set up at the USA science and engineering festival last year and the kids loved some of the experiments they had set up!
Science Experiment Pack: Back about five months ago I made a packet of some of our most beloved science experiments. If you’re keen to do science experiments with your kids, here are some of the things that my kids and I have enjoyed a lot:
Download your free Science Experiment Packet here.
You can find more of our science experiments by clicking on the categories button in the right sidebar. Or, you can find activities related to different science topics we’ve covered such as
Have fun experimenting with your young scientist!!
I’ll be taking some time off with my family and will return next Wednesday with more of our homeschool adventures.
Have a safe and Happy Thanksgiving holiday!
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Friday, November 16th, 2012
Our chemistry textbook also talked about acid-base reactions. It explained how antacids can help neutralize the strong acids in your stomach. We contrasted this slow reaction…
to the more impressive reaction of baking soda and vinegar! DD was putting her fingers in to see how her stomach would feel.
If you haven’t already done Bubble Bombs with your kids, be sure to do that as well! You take a ziploc bag and pour vinegar into it. Then place baking soda on a tissue paper and hold it up at the top as you zip the bag closed. Let go of the tissue letting the baking soda fall into the vinegar. It reacts quickly!
We first did this at least five years ago — and just a few weeks ago he rounded up all the ingredients and did this for a long time out in the yard with ED!!
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Monday, November 5th, 2012
We did a lot of Montessori science when the older kids were little, so this is an experiment we did years ago. Now the older kids are studying chemistry and ED is the perfect age (4) to enjoy the action of this experiment. Using red cabbage juice as the indicator, you add various household ingredients and compare it to an acid-base chart to see where that particular item falls on the scale.
Before we did the experiment, we read a couple of chapters from Real Science 4 Kids, Chemistry that talked about the differences between acids and bases. (See the picture below, right. You can visit their site for a preview of the student textbook. We don’t have the other materials such as the teacher’s manual, but I really love and highly recommend the textbooks.) I love the cute illustrations that show the bonds between atoms as linked arms. After finishing our reading, I told the kids to write a quick page for their science notebook that shows that bases (often) have an OH group and acids have an H group:
Then we went into the kitchen to explore which household items were acids and which were bases.
First we cut up red cabbage and placed it in a saucepan with water, brought it to a boil, turned off the heat and let it sit for a number of hours.
Then we strained out the cabbage and poured the juice into test tubes.
We had a huge selection of items to test — partly because there are three kids who all want to take part in the action. If I had to narrow down the selection I would recommend
- Diet Coke
- baking soda
- glass cleaner
- apple (but let it soak overnight before really assessing the results)
- hydrogen peroxide (because it bleaches the color out)
Here was our setup:
Before we started adding the ingredients to the test tube, I had the kids decide together which they thought were acids and which were bases.
After adding all the ingredients to the test tubes and labeling them, we looked for the top two most acidic items and the top two bases.
Just so you know, we found the results easier to determine after adding some water to the test tubes because I had let the cabbage sit on the stove for a long, long time and the indicator was quite strong.
You can find the acid-base color chart at Surfing Scientist (page 13) or just google “acid base color indicator chart.”
We used plastic test tubes that we got from Oriental Trading a while back, but of course you can use disposable plastic cups, baby food jars or whatever you have on hand. This was our set up a few years ago:
You can freeze the red cabbage juice for later use.
I put this into a pdf if you’d like to print out my explanation/directions for this experiment.
Making Red Cabbage Acid-Base Indicator
Another wonderful resource is the Surfing Scientist which has much more detail about this experiment.
You might also be interested in these posts from our chemistry unit:
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Friday, October 12th, 2012
We moved on from talking about atoms to talking about molecules and chemical bonds. Since my kids are pretty young, this is just a basic introduction to how bonds are formed and made.
Building Molecules Worksheet:
The screen shot below shows 2 of 3 pages.
We spent several days building different kinds of molecules:
On the first day we built water, oxygen, hydrogen and hydrogen peroxide:
The next day the kids built carbon dioxide, chlorine, ammonia and acetylene gas:
And on the last day they built methane gas, ethylene gas, methanol (wood alcohol), propane gas, nitrous oxide (laughing gas), vinegar and others:
We used EIN-O’s molecule kit. It doesn’t have the best reviews on Amazon, but it was just fine for our needs. It comes with double-bonds (see the red oxygen molecule above) as well as the plain single bond pieces. It is a bit confusing that there would be more than one hole on the hydrogen (white balls), but I just told the kids that was how the balls were made and they were fine with that explanation.
Again, if you’re interested in building the molecules we did you can download the worksheet I made by clicking on this link–Building Molecules Worksheet.
You might also be interested in these posts from our chemistry unit:
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Chemistry Unit, Freebies, Homeschool Den, Must Read, Science
Tuesday, October 9th, 2012
Matter is made of tiny particles that are attracted to one another.
We did a series of experiments activities from Middle School Chemistry (the free, downloadable chemistry course) that show that water molecules are, indeed attracted to one another.
We first used a medicine dropper to see how much water we could push out of the syringe. We also examined the pictures of the droplets we managed to photograph in the air. We observed the shape of the droplets and talked about why the water drop was round (rather than in a thin stream or bursting out in all directions).
We then put a few drops of water on wax paper and tried moving it around with a Popsicle stick, tried separating it and watched what happened when two droplets were brought in close proximity to one another.
We did the activity, Water Drops Unite!, using the sheet provided in Middle School Chemistry. The kids had a race to see who could unite the water droplets the fastest.
The kids also had fun with the Race Drop Raceway.
The kids were amazed at the water balloon video that showed frame-by-frame how even after a balloon is popped, the water molecules stay together and keep the shape of the balloon. We must have watched that video four or five times!!
From here we went on to build our own water molecules (and others). More on that in another post soon.
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