I need and object that will sink for one minute and then float...?

Question

I have to do an experiment about density. we have to find an object the will sink to the bottom of a tub filled with water (about a foot or so of water) and then after exactly one minute of staying on the bottom it has to float. Our teacher suggested something that gives of a gas (non toxic) or something that will decrease in mass or increase in volume. the density has to change for it to be able to float... any ideas.... i was thinking of tying an object to a sugar cube but i haven't tried it yet and i would really like other ideas...

Answer 1

Any good scientist knows that in order to find a solution to a problem you have to try different things.
Why don't you try your sugar cube idea and see what happens. Document it. If it doesn't work, try something else. Keep trying different things until you find the conclusion that you're looking for. Science can be fun! Enjoy it.

Answer 2

Tie a float (cork or bulb) to a small porous bag. Put a measured amount of common table salt in this bag and place it into your tub. Put enough salt into the bag to be heavy enough to sink the float. Start a timer. After a few minutes the salt will start to dissolve and difuse into the tub. When enough of the salt has disolved, the float's buoyancy will bring the bag to the surface.

Two ways to figure out how much salt to use: 1) Experiment with the quantity of salt needed to make the float rise in 1 minute or 2) theoretical - calcuate the average disolution time of an ionic (sodium chloride) of that granular size in that temperature of water to get the same answer. I frankly think the experimental answer is going to be quicker and more accurate.

Answer 3

Here's one I have made before:
Get a pill bottle with a loose top.
Place one or two coins inside the top so that the bottle will sink when it is filled with water.
Get some fizzy denture cleaner and brake off a small piece and wrap it with a bit of foil, loosely.
Fill the bottle with water.
Drop in the coins and the denture cleaner and turn the bottle upside down (cap down) while it's under water.
The coins will sink the bottle to the bottom. When the fizz leaks from the foil wrapped cleaner it will force out the water and the bottle will float back to the top.

Answer 4

It has to be in water?
A rasion dropped into a carbinated beverage will sink, then float, then sink and float again as it pickes up the carbon dioxide, then rises to the surface where it releases the gas.
Come to think of it, when I cook kidney beans, they sink at first, then float after they have been boiling for a few minutes. They swell up by absorbing water, that changes the density.
Does this help, or am I just rambling again???

Answer 5

Just a thought, you would have to play around a bit to get the timing down, how about using Alka Seltzer? It will start to produce bubbles as soon as it is in the water. You need something to capture those bubbles, like a sponge or something. So slit some holes into the sponge with a razor, slide in as many Alka Seltzers as you need to do the job in one minute. You might have to add weight to the sponge to start to get it to sink right away. Get some fishing weights and attack on to each corner of the sponge.

Answer 6

human

Answer 7

Ummm...well according to corkis' first law of density.......lol i hate mr's gay don't you!