I need to make an object float, sink, then float again without touching it after putting it in the water.?

Question

Right now, I have a spice container with holes in the bottom. It floats, then fills up with water and starts to sink.

Before I put the container in the water, I fill it a little with either baking soda or vinegar, then put a piece of paper towel in the middle of the container, and then I put the other substance in in order to form CO2 bubbles, so the container floats back to the surface.

I'm having a problem though. It floats, then the reaction happens, and it never sinks.

I need to figure out a way to delay the reaction until after the container has filled up with water and has sank.

Suggestions?
Any other ideas would also be helpful!

Answer 1

How about making a 'wick' out of something else? This is only an idea, but say you put the baking soda in, then a layer of salt, and then put your vinegar in? The vinegar should soak slowly through the salt but once it reaches the baking soda the gas will emerge and the salt will be partially dissolved so it will let the gas out. You'll probably have to experiment a bit with what to use (salt is the first thing I thought of) and how much of it gives you the right soaking time; and also how much vinegar to put in (you'll need more as some will just soak into the wick I think).



Hope you figure it out anyway :)

Answer 2

Baking powder alone will do what you want (you're right, soda won't do a thing). You will need a small chamber perforated underneath (like a salt shaker?) with a skirt projecting below that around the powder chamber bottom. The baking soda will make bubbles in the water at the bottom of your chamber, filling the skirt area until displacing the sub's weight, and then it will rise. Once it reaches the surface, the sub's top weight should tip the hull on its side, allowing the bubbles to escape. The sub will then roll upright again and sink. More bubbles will be forming. When you get enough the sub will rise again, repeating the process. The smaller the better in this case as weights and measures are important. In fact, I'd try just the 3" tube and bubble chamber first, just to gather some imperical data. Make the sub about the size of your finger, maybe, and the chamber should hold about a quarter or half teaspoon of baking powder (more won't work as well, and makes a bigger mess). The sub should be trimmed carefully fore and aft so that it floats level and it should have enough top weight (a sail or conning tower shape) to tip the sub over on the surface, but not to disturb its center of gravity and center of buoyancy in water. My best guess would be to make it from something like thin walled 3/4" PVC pipe with a hole drilled halfway through at the mid-point to accept a 1/2" pipe cap glued in upside down. If you need to, then cap the ends of the hull with PVC plugs (or corks, or whatever). The inverted pipe cap will be your baking powder chamber. Fit a perforated plate (a stiff piece of screen will do) and make it removable so you can clean the chamber and recharge your baking powder. The bubble chamber should be pretty small, maybe big enough for the tip of your little finger--probably not more. Keep the whole sub to maybe 3" long overall and see if you can't get it to work without buoyancy chambers and trim weights (smaller and lighter is better--heavy enough to sink, but not much). Remember, the smaller you keep the displaced volume, the smaller you can keep the sub overall. It needs to be negatively buoyant, but just enough so that a couple of bubbles will give it a few grams of positive displacement so that it can surface. Anything more is just too much to ask. One more trick here is to make the bubble skirt tapered inside. This will feed the bubbles overboard faster when the sub rolls, keeping it from lying there trying to burp before diving again. You could use a counter-sink drill to make the cone and make it to hold your screen and to be the plug that holds everything together. Good luck and keep us up to date.

Answer 3

Fold the paper towel a few times before you stuff it in. The more paper towel you put in, the longer the delay. Also you could try a higher quality paper towel. Cheaper brands tend to dissolve faster.

Answer 4

Pop a raisin in a glass of lemonade, it will float and sink repeatedly, because bubbles attach to the raisin and make it float, then pop when the raisin reaches the top. Hope this helps.

Answer 5

put a piece of stirofoam in it