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mass,volume,density
01-18-2009, 11:48 AM
 #1

I am having a very hard time on trying to teach mass, volume, density, and weight. Does anyone have any lessons or activities they can share?

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Mass/volume/density
01-18-2009, 04:34 PM
 #2

I have the kids measure the mass and volume of different objects. We don't do density in grade 5 at my school, but sometimes I explain it's like packing a suitcase with five sweaters and 50 sweaters. Same size object, just with more molecules in it.

Edmund Scientifics has a good set of density cubes, several cubes with the same volume but different mass and density.

I also have a track at trackstar that I use with the kids, if you want to take a look. trackstar.4teachers.org, and it's track #275986

 Firebelly Joined: Jan 2009 Posts: 793 Senior Member
Firebelly

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I Just Did Something With That
01-18-2009, 04:34 PM
 #3

I filled up a small fish tank with water. I placed a can of diet pepsi and a can of regular mountain dew in it. The mountain dew sank and the diet pepsi floated. Before putting the cans in the water, we talked about the two cans having the same volume (size and weight). The mountain dew sinks because it has more density than the water around it. The diet pepsi floats because it has less density than the water. The difference is the amount of sweetener used in each. The mountain dew uses much more sugar than the diet uses of aspartame.

The next step of this is to change the density of the water and therefore make the mountain dew float. To accomplish this, add salt to the tank. Keep adding it and stirring it in. I actually left it alone while we read our textbook. Periodically, I added more salt. Within ten minutes, there was enough salt dissolved to make the water now more dense than the mountain dew. It worked well. The kids were very enthused.

I have tried it with pepsi instead of mountain dew, but the pepsi floated for some reason (too much of an air bubble in the can??) I would make sure your regular soda sinks before you do this in front of the class!

 BellJ Joined: Aug 2007 Posts: 299 Full Member
BellJ

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mass and volume
01-18-2009, 04:57 PM
 #4

One thing I did to demonstrate mass and volume was take an empty cola can. We discussed its mass and weighed it and it's volume as the amount of space it took it up. Then, I placed the can on the floor and stomped it. (They loved that). We discussed how the mass didn't change but the volume did.

You could easily discuss density with the demonstration too.

 lola_fish Joined: Dec 2008 Posts: 13 New Member
lola_fish

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mass, volume & density
01-21-2009, 06:35 PM
 #5

we have also just begun learning about mass, weight, volume & density. i think a lot of hands on learning has really helped them. i've let them find the mass, volume and density of various objects. I, too, had also compared density to a suitcase...i guess because density is based on how "packed" the molecules are in an object.

We use an online system called CSCOPE and one example they give to show density is to use an egg demonstration.

You fill 1st glass 1/2 full with water and put an egg in. Have them observe, then add 3 tbsp. salt and gently stir. It should rise.

You then fill 2nd glass 1/2 full with water then stir in 10 tbsp. salt. Let it settle. Then SLOWLY add more water until the cup is full. DO NOT STIR, and gently lower the egg into the water. The egg should be suspended between the regular water and salt. water.

Good luck!

 trasie Joined: Jul 2008 Posts: 3,788 Senior Member
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Similar to Lola_Fish
01-22-2009, 03:43 PM
 #6

After teaching density I dissolve salt in water until no more will dissolve. Pour that into a clear plastic tennis ball container and float a golf ball on it. VERY carefully pour water on top (I try to pour it down the side of the container. It looks like the tennis ball is floating. Display this in the classroom but don't let the students handle because the movement could cause the salt and plain water to mix and ruin the demo. It looks like magic! The students are mystified! After a few days of guessing I give clues until they "get it."

Thanks for reminding me about this experiment Lola_Fish. I haven't done this for a few years but I just finished teaching density so.....

 future teach Guest
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response
02-03-2009, 10:28 AM
 #7

That is so cool! I'm definitely going to use this idea!

 Boberhaus Guest
Boberhaus

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Reason MT. Dew sank and Pepsi floated
03-06-2009, 10:14 AM
 #8

The experiment has to do with density. The mountain Dew is more Dense because it has more sugar than the pepsi. The Density of pepsi is less than 1 since it has less sugar than mt. Dew.

 trasie Joined: Jul 2008 Posts: 3,788 Senior Member
trasie

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03-07-2009, 08:29 AM
 #9

it looks like the golf ball is floating in the middle of the container.

 yesteach Joined: May 2006 Posts: 9,914 Senior Member
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Mass and Weight
03-07-2009, 11:15 AM
 #10

When I taught sixth grade we always used the gravitational pull of the planets to discuss mass and weight (since that's what weight is).

We would find the students' mass by placing them on a scale. And then discuss that weight and mass on Earth are the same number, because we base weight on the gravitational pull of the Earth... However, if we were to travel to the moon, our weight would change... but our mass would remain the same - unless you lose an arm on the way to the moon.. (6th graders appreciate warped humour ). They'd then find their "weight" on various planets based on the gravitational pull of the planet... yet note that their mass always remained the same. It at least helped them have a better definition of the two words.

As for volume and density - we used balls that were the same size - ping pong balls and really big steel ball bearings I found.. We could measure and determine that their volume was the same... Then we would find the mass of the two items using balances and using the formula for density, determine the density of each object.

For a visual - with my fourth graders we used five colors of water - each with varying amounts of salt in a 4 oz bottle of water - none, 1 tsp, 2 tsp, 4 tsp, 8 tsp. (this one wouldn't even totally dissolved because it became so saturated). Each group then used a pipette to add 50 drops of the colored water to their test tube. It has to be done carefully and drip it slowly down the side of the tube so it can displace where it needs to. If done correctly, they end up with a lovely striped test tube. It works with different liquers also, but probably not the best thing to use with fifth graders..

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