Lesson 20
Science of Density
Science Standards Addressed:
- Describe the characteristics of the 3 states of matter (solid, liquid, gas).
- Describe how matter is ordered in solids, liquids, and gases and the changes that occur to them when heated.
Plus we snuck in some speaking and listening standards like asking questions, expressing ideas, following multi-step directions, and participating in discussions.
As the children arrived, to go along with our density is like kids packed into a school bus analogy, we played the songs Don’t Stand So Close to Me, by the Police; The Wheels on the Bus, and My Name is Cheech the School Bus Driver, by Cheech Marin.
This is what we put out in the snack area. It was pretty much one of everything from the produce section of the grocery store plus diet and regular sodas. We pretended this was a normal snack. We let the kids be confused for a bit and then brought out a normal snack.
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| All of this stuff was for some fun experiments on density (below). |
To sneak in some literacy standards, while they ate snack Madison read The Ogs Learn to Float, by Felicity Everett
a book about a family of cave people who experience a flood that wipes out the town. This book tells how granny goes after her cookbook and is pushed out of the house! The family tries to rescue granny but can’t float until Grandpa builds a boat to sail out to granny. The whole town is completely under water except the tip of the schoolhouse and that’s where granny is! Read this book to find out what happens next. J
Another book to sneak in some literacy is Who Sank the Boat? By Pamela Allen. Beside the sea, there once lived a cow, a donkey, a sheep, a pig, and a tiny little mouse. One warm, sunny morning--for no particular reason--they decided to go for a row in the bay. Do you know who sank the boat? "Funny . . . just right for the very young."--The New Yorker.
Link to the book.
“Lite” Rice
To engage their emotions and create a sense of wonder, we started off with this neat trick. Steve Spangler says this trick dates back a few thousand years. You’ll need two empty water/soda bottles, some rice two chopsticks, and a good acting face. We took two empty water bottles, labeled one as “Lite Rice” and the other one we labeled “Rice.” We filled both bottles almost full and then we shook the “Rice” bottle to fluff it up and make it appear full. To the “Lite Rice” bottle we packed the rice down and added more, and tapped it on the table and jabbed it with our chopsticks to pack it down even more until it was completely full.
Then I gently lifted my chopstick into the air and asked the volunteer to do the same. My bottle of “Lite Rice” raised into the air, while the normal rice remained on the table – Ta Da!
When we asked for possible explanations for what they observed, we heard funny possibilities – like magnets and glue! Really it’s the higher density of rice in the “Lite” bottle. They are jammed in there so tightly that when the chopstick is added, there is enough friction from the rice to grab onto the chopstick and keep it in place.
School Bus Analogy
D=m/v Density is just a ratio comparing two quantities –mass/volume. To make it really simple, we call it stuff per space. We showed them two pieces of paper – the same size- same area - equal space. Number of paperclips per piece of paper is stuff per space – density.  |
| 16 paperclips/space |
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| 9 paperclips/space |
When we talk about density, we always use the school bus metaphor. We tell the kids that in most school busses there are 11 rows of 2 seats – if kids sit 3 per seat – that means the density is 66 kids/bus. We ask, “Could we have LESS than 66 kids/bus?” They say of course! We ask, “Could we have MORE than 66 kids on the bus?” They say – no way – 3 per seat is FULL. They’ve been there – done that! We say what if we make kids sit 6 per seat – sit in each other’s laps? Not fun, but is it possible? OK – it’s possible to get 132 kids/bus. We ask, “What if we made it a contest. You guys stuffed yourselves UNDER the seats, on the backs of the seats, kids on top of kids on top of kids?” They have a lot of fun just thinking about this possibility! Density is stuff per space – in this instance kids per bus. You could have 1 child/bus or you could have HUNDREDS of children/bus!
We talked about how matter is arranged in solids, liquids and gasses and what happens to matter when it is heated up. We showed them these models Dad made by embedding BB’s and pellets in plastic. The model where it looks like BB’s are floating – rarely touching each other is like a gas. The model where the BB’s form a layer covering the entire area is like a liquid (takes the shape of it’s container). The model where the BB’s are toughing tightly and remain in their own shape is like a solid. The gas model is very lightweight and the solid model is HEAVY!
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| Dad even wore his special Solid, Liquid, Gas… They ALL Matter t-shirt! Such a dork. |
Sink or Float?
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| We took a cue from Dave Letterman and asked the question, “Sink… or Float?” |
We said, “Kids bring me some water. As they filled some large containers, we played Somebody Bring Me Some Water, by Melissa Etheridge.
We took all the produce we pretended was for snack and made predictions about whether each would sink or float. Then we tested it out and talked about our observations. The little key limes sank and the bigger limes floated.
When we peeled fruit we noticed the key lime peel was very thick and tough – dense, but the orange and big limes were more spongy – less dense. The kids said the poofy rinds were like life jackets that made the fruit float – nice analogy!
Coke Floats
After experimenting with all the produce, we asked – cans of soda – sink or float? There was no consensus. Some of the kids had been wrong so many times, no longer wanted to say their prediction out loud – which was fine – they’re still thinking!
Then we dumped a bunch of various cans of soda into the water.
After a short time, they noticed something that the floating cans had in common – they were all DIET. There had to be more stuff/can in the regular sodas. The regular cans MUST be more heavy than the diet cans – right? We had to find out, so we weighed the cans.
There was a big difference
The diet sodas weighed much less than their counterparts.
When we looked at the label, we could easily tell why. The regular sodas had everywhere from 39 – 41 grams of sugar. We asked them how much sugar they thought 41 grams was. We showed them a sugar packet – like they have in restaurants. We asked how many packets they thought would make 41 grams. We asked them how many packets of sugar their parents would let them put into their drinks. Most kids said one or two packets.
So we did an experiment to find out. We set the scale to 41 grams and began emptying sugar packets onto it. They were surprised a 4 packets. We kept going. They were shocked that it took MORE than 10 packets and we still weren’t at 41 grams. In our experiment it took 13 and a half packets to get to 41 grams - 13 PACKETS!!! In 1 can of soda!!!
That’s bananas!
Full description from Steve
Bowling Balls
As the grand finale’ we asked one more sink or float prediction question – BOWLING BALLS?
We showed them 2 bowling balls. Most of the kids thought they would sink. Why? Because bowling balls are heavy! Only one child was onto us. He thought maybe a child’s ball would float and an adult’s ball might sink. He was right. One of the ball weighed 8 pounds and the other weighed 15 pounds. The 8 pound bowling ball is about the same weight as a gallon of water, but it takes up MORE space than a gallon of water (it is less dense than water), so it floats.. The 15-pound ball is more dense than water so it sinks.
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| The surprising floating bowling ball! |
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