Use this heterogeneous mixture experiment to teach your kids some of the basic concepts of chemistry. Building a good foundation of knowledge and understanding makes future chemistry studies easier and more interesting.
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The Oxford Dictionary definition of chemistry is this…
“the branch of science that deals with the identification of the substances of which matter is composed; the investigation of their properties and the ways in which they interact, combine, and change; and the use of these processes to form new substances.”
That means, at its base, chemistry is just figuring out what stuff is and what happens when you mix it together. It’s like baking a cake. In fact, baking is chemistry. We need to know what the ingredients are and how those ingredients react with each other when mixed and heated. If we don’t, the cake won’t turn out the way we want it to, and we all want a good cake!
When we think of chemistry like that, it seems pretty simple.
Breaking down a complex science like chemistry into simple blocks of information makes understanding it easier and takes some of the intimidation out of it. Let’s look at one simple aspect of chemistry that all kids like – mixing stuff together.
The Chemistry Of Mixtures
When substances are combined, one of two things happens. Either chemical bonds form and a new substance is created or there is no bonding and a mixture is formed. Chemical bonds happen on a atomic level and are hard to separate, but mixtures can easily be separated.
To learn more about atoms and molecules, check out the Beginners Guide To Atoms And The Periodic Table.
There are two main types of mixtures – heterogeneous and homogeneous. In a heterogeneous mixture, the substances are not uniform or evenly distributed. Think Chex Mix, Lucky Charms cereal, chocolate chip cookies, and sand. All are made of different components that can be seen within the mixture. These components may not be evenly distributed and be easily picked out of the mixture.
In a homogeneous mixture, substances are combined and are distributed uniformly throughout the mixture so that the mixture looks like one substance, but can still be separated by various means. Shampoo, hand soap, salt water, and apple juice are all examples of homogeneous mixtures.
Heterogeneous Mixture Experiment
When I was young, I loved our sandbox. It was framed by 4 railroad ties that were left when the railroad tracks near our family farm were abandoned and dismantled. The sand was gathered by a tractor and end-loader from the creek that ran through our pasture.
The grains of the sand were varied with colors ranging from shiny, transparent quartz to the brown, orange, and black colors of assorted rocks and minerals. Then, there were the snail shells. Teeny, tiny shells that I separated out and kept in an old measuring cup my mom gave us to use as a sandbox toy.
Sand is an example of a heterogeneous mixture. Look closely at a handful of sand and you will see all the different colors and shapes of the substances that make up sand. You might need a hand lens (magnifying glass) to really see, but the variations are there. (For an even more fascinating view of sand, check it out under a microscope!)
Try this experiment with sand from your sandbox or from your last trip to the beach. (I seriously had enough to do this with sand still in the bottom of our beach bag from over a year ago!) It is a fascinating look at what particles make up the heterogeneous mixture of sand and in what percentages.
I discovered this experiment a few years ago when we reviewed By Design Science, a wonderful inquiry-based science curriculum. This experiment is one of many engaging hands-on activities found in the level 8 program.
Mixture Experiment Supplies
All you need for this experiment is a hand lens (magnifying glass), a toothpick, and sand.
Spread approximately 1 teaspoon of sand out on a white piece of paper in a single layer.
Using the hand lens and the toothpick, count out 100 grains of sand.
Sort the 100 grains of sand into groups according to the color and other characteristics listed in the Sand Key at the bottom of the post.
Count the number of grains in each group and calculate the percentage each group makes up of the whole 100 grains.
Construct a bar graph showing the percentage of each group of sand grains.
To be sure the sand sample you sorted is a good representation of the sand as a whole, try this 3 more times recording results each time. You can combine the results and find averages. This gives your results a higher confidence level.
Try this with sand from different sources and compare your results. To see examples of sand from different beaches, check out Comparing Beach Sand Under The Microscope.
Questions To Answer
Here are some questions you might ask your kids when they finish the experiment to get them thinking and to show they understood the results of the experiment.
How many different groups of sand grains did you discover?
Which type of sand grain was most common?
Did you find any organic matter? What type?
If you used multiple sand sources, what were the main differences in the sand?
Use this sand key as a guide to sorting your sand. You may not find all these types of particles in your sand.
Calcite – pure white
Feldspar – opaque, white to gray, sometimes red
Muscovite mica – white to gray, transparent, paper-like
Quartz – colorless, semitransparent, glassy appearance
Pyrite – light brassy yellow, cubic structure
Biotite mica – brown to black, paper-like
Iron – black, dark brown, magnetic
Homblende – green to black
Organic material – bits of wood, leaves, etc.