please help! how to keep ice frozen?

Question

I have a science project to do, and the concept is, use a plastic case and put things on it or in it so that it will keep an icecube frozen for an hour. I need to put insulators in it. any ideas?
thanks in advance for the help.

Answer 1

put another icecube in the plastic case,

Answer 2

Remember the main fact about heat, is that heat rises. Heat rising from bottom to top is what will make the ice cube melt fastest, not what is around it. The second factor would be the ambient air around the ice cube. Stop both of them, and you stop the melt. Anything you can put underneath the cube, such as insulation, foam, etc might help to stop heat transfer up. Also, if allowed, insulate around the side and even the top of the ice cube. If I could get away with it, I would fill the entire plastic box with an insulation material, like foam or fiberglass, except for the small area that only exactly fits the ice cube. I am not clear whether the rules of this project allow you to enclose the cube in something else, but if not, the area under the ice cube should be your focus.

I'm not clear on the rules here, so I'm no sure what is allowed or not. If you are allowed to put other cold objects within the tank, freezing large gravel or even bricks will help keep cold inside. Also, if you use dry ice, the pelletized version is better. It "melts" faster, but keeps things colder. Again, under is better than around. Also, don't forget to never touch dry ice with bare skin, as the severe cold will cause a "burn" to skin.

Another idea would be to think about the plastic case's environment. In an 80 degree room, the ice cube might melt fast. But, if you were allowed to submerse a sealed plastic box in 40 degree water and weight it down, the cube would melt much slower. This might be another option to consider, if allowed.

Hope this helps.

Answer 3

Hi, This sounds like a year 4 or year 10 project - so I guess that creating a vacuum and dry ice may be a bit impractical.

Try Lining the plasic case with large bubble wrap, then placing the icecube inside a smaller glass or mirror case that fits inside the bigger plastic case. This should then act like a flask, the trick is i think to make sure that the two containers are not touching. else there will be a direct route for heat to enter and melt the ice.

This way you will have a kind of thermos effect where the trapped air bubbles will act as an insulator and the small glass or mirror container will reflect any heat entering back out again- (even try clear plastic).

You will need to test this because it is just a theory at the moment


Here is a flashcard that may help
http://www.2soma.com/physics_flashcards/insulators.htm

Answer 4

This sounds like an interesting design problem. Ice melts because it takes
in heat from it's warmer environment. Your goal is to shut down those
routes for heat transmission as effectively as you can. Some materials,
like metals, are very good at transferring heat to the ice. So you want to
avoid these--at least don't let these kinds of materials make contact with
the ice. Most plastics and wood, on the other hand, are poor at
transferring heat--these are the materials you want to use to hold the ice.
Keep the system for holding the ice as simple as possible--that is,
minimize contact with the ice. Now, besides whatever is holding up you
ice, you ice is also in contact with air. Air is not a great conductor of
heat, but it does work. It would be great if you could remove the air, but
that's probably not feasible for you. Removing the air requires creating a
vacuum, and that requires the right equipment and vessels. But what you
can do is create a "dead air" space. Simply surround the ice with a small
box that creates a quiet air space around the ice cube. If this box is an
insulating material--like styrofoam or even cardboard, then all the better.
For added protection , place all this in another insulating box. The air
in the inner box will be cooled, causing some warming of the ice. But once
this air is cooled down, it should not keep losing heat to the ice.


If this doesn't go against the rules, place a pre-cooled object into the
inner box. A piece of metal (coins would do the trick) pre-cooled in the
freezer, for example, would help to maintain the cool environment for much
longer.

Answer 5

There are two things that will keep prolong the life of the ice.

1. Increase the thermal resistance to the outside world. Air is good but it will circulate you'll constantly get warm air next to the box. Styrofoam is a good insulator. The thicker the better.

2. The other way is to raise the outside temperature so that the inside stays cold. Put the ice in the box and then put the box in the freezer. Or, go buy those cold packs that you put on sports injuries. Put the ice in the box and the packs on the outside. If the box sits in the sun, put a mirror to reflect the sunlight away.

Good luck

Answer 6

I'm guessing that you don't have dry ice (frozen CO2), and putting it in a freezer doesn't count. Two ice cubes last longer than one, but two ice cubes aren't any colder than one. Here's something easy no one has suggested:
If you mix salt and ice, the temperature drops below the freezing point of pure (or tap) water. That's why salt melts ice...it drops the melting point below the outdoor below zero temperature.
So...in your insulated box where you are trying to keep an ice cube from melting, put a container with another ice cube (or several) on which you have sprinkled some salt. Those cubes will melt, but the temperature inside the box will go down below (perhaps to minus 5 or 6, depending on amount of ice and salt). That will keep the first ice cube (the one without the salt) from melting.

Answer 7

Anything you can put underneath the cube, such as insulation, foam, etc might help to stop heat transfer up. Also, if allowed, insulate around the side and even the top of the ice cube. If I could get away with it, I would fill the entire plastic box with an insulation material, like foam or fiberglass, except for the small area that only exactly fits the ice cube. I am not clear whether the rules of this project allow you to enclose the cube in something else, but if not, the area under the ice cube should be your focus.

Answer 8

No you don't want an insulator IN it. Drop a glass marble or a steel nut (as in nut and bolt) into the container. This solid mass will retain it's cold temp longer than frozen water because of it's density. Surround the ice with an insulator to keep the heat away. Use pieces of a styrofoam coffee cup to make a shell around the ice. And lastly, freeze in your main freezer as typically these are set lower than the freezer/refrigerator in your kitchen. Keep this in mind, you can't ADD cold, you can only REMOVE heat.

Answer 9

line the plastic case with tin foil, get a bigger plastic container. Fill that with anti-freeze and submerge your case in that.

Anti-freeze absorbs heat energy. We did this experiment in honors chem like 14 years ago where we measured the temp of water in a test tube that was surrounded by ice. The water went to 0 degrees Celsius, but when we added anti-freeze to the water it actually went bellow freezing!

I would add some water to the anti-freeze as well. Water has a specific heat capacity that is 4 times that of air. Go 50/50, it's what i use in my car. Hey there's a reason why they call it an engine coolent

ideally you would make your box air tight and put it in a vacuum, but i suppose this is not possible. Vacuums have very few molecules to absorb heat.

The anti-freeze will absorb heat energy from the air, and also from your plastic container.

Answer 10

you're in trouble before you begin. you need to better define your experiment.

what EXACTLY do you mean "keep an icecube frozen for an hour" -- absolutely no melting? 20% melting? ...

what EXACTLY is your experiment trying to prove?
state the problem as such and such won't happen under such and such condition, and if that something does happen, then your experiment has proven something. otherwise your experiment merely fails to prove anything.

how are you controlling the external conditions? if for example, one trial is done with your container set on the sidewalk in the mid-day sun and another trial at midnight, you don't have a controlled experiment (unless of course, that is the only thing you are changing)

are you comparing different insulation materials or perhaps different thicknesses of the same material? again, define your experiment clearly and don't have a bunch of different things changing at the same time so that no real conclusion can be made.

ok, i'm bored. ask your teacher for more advice.

Answer 11

Look up the triple point of water. This should tell you the temperature and pressure where water exists in all three states.

This should also give you a graph telling you under water conditions water will remain frozen at room temperature (you will need to create a vacuum).

Depending on whether this is for high school or college a little research into thermodynamics might not hurt either.