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DO ALL SOLIDS
DISSOLVE IN LIQUID?
Here we have four jars. Into each jar, we will measure 1/2 cup of water. Each jar gets a sticker with its number on it, and we will write down the numbers, leaving a space beside each number and two lines under each number.
Jar #1 gets one teaspoon of brown sugar (leave the spoon in the jar and use a new spoon for each jar); into jar #2, we can put one teaspoon of salt; jar #3 will have one teaspoon of sand, and into jar #4 we will put some wood shavings from the pencil sharpener.
Let's stir them all, very carefully to make sure everything gets mixed well.
On your lists, make notes of what happens after the mixtures are stirred. The brown sugar sort of melts, and seems to go away, but the water has a little bit of color to it. That means that the sugar dissolved in the water--it became a part of the water. Since the water is cold, if we let the jar sit for awhile, there will be a little sugar down on the bottom of the jar. If we had boiled the water, the sugar would be completely dissolved, and would never separate from the water and go down to the bottom of the jar.
seems to disappear, also, doesn't it? Yes, it dissolves, too. If we let
this jar sit for a week or so, the water would evaporate, and the salt
would form a little crust
How about the sand in jar #3? While it is being stirred, it swirls around in the water, but what happens when we stop stirring? There it is, all of it, down on the bottom of the jar. It looks like sand does not dissolve. (How many of you know how sand is made, and what it is before it is sand?)
We know how the wood shavings were made before we put them into the last jar. What does that stuff do? It follows the spoon around while we stir, but then when we stop stirring, where does it go? Does it dissolve? Does it sink to the bottom and lie there in a lump?
Let's do the same experiment now, but use cooking oil instead of water. I guess you will learn why it is that mom shakes the salad dressing before she pours it onto the lettuce. The substances that dissolved in the water did not quite dissolve in the oil. When you get home, ask mom if you can look at the salad dressing, shake it, and watch what it does.
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