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Answers to Readers' Questions on Physical Science:

Thermos

The following 25 comments and questions have been sent in. They are listed according to date.

List of first 10 items

• Is it possible to build a 50 gallon thermos?
• Make a thermos to keep a drink warm 3 hours
• Suggestions to improve info on thermos containers
• Would a Styrofoam container keep ice cream cold?
• Need to keep a can cold for 5 hours
• Should I use newspaper for my thermos?
• Should I put shiney aluminum foil in my thermos?
• Have to insulate a chocolate bar
• Is a thermos made in China safe to use?
• Needs to keep water warm for 6 hours

Next 10

Is it possible to build a 50 gallon thermos?

Question

March 24, 2009

I am in the 10th grade and have been thinking of something for some time now. Would it be possible to build a 50 gallon Thermos bottle? If a Thermos bottle can keep water hot for many hours, wouldn't the same science work to keep water hot in home water heaters? I thought of using a heavy duty plastic tank with an interior reflective flask, and vacuum sealed. Conclusion? fuel sourse would not come on as often, thus saving the homeowner lots of money each year. I would like to know what others think about this idea? Thank you from Virginia, USA

Joe - USA

17502

Answer

Your idea is good, but to a degree it has already been done.

The hot water heater in most homes can be thought of as a large thermos bottle. Typically, the container for the water is wrapped in a layer of insulating material and then held in place with the outer steel shell. Some inexpensive water heaters have a thin layer of insulation. If the out shell feels warm to the touch, people can buy a fiberglass insulation blanket to wrap around it.

With a small thermos bottle, the area between the inner container and outer container is often a vacuum. But evacuating a large container is too expensive to be practical. That is why they use insulating material.

Keep think of the ideas. That is how progress is made.

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Make a thermos to keep a drink warm 3 hours

Question

March 18, 2009

With this learning and understanding, how could I make a thermos to keep a drink warm for over 3 hours by using materials i can find in my house. Or how would i make a vacuum to use a an insulator??

Danielle - Canada

17469

Answer

You can wrap a container in insulating material such as Styrofoam, bubble wrap, a wool scarf, or layers of newspaper. It must be thick enough to keep the heat in. The cover must also be insulated.

You will have to experiment and try things out to see what works the best and how thick you need the material.

Look at the Answers to Readers' Questions to see what other students tried.

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Suggestions to improve info on thermos containers

Question

February 25, 2009

This information I think can be very iseful for people studying heat. Just for something you might want to add to your website is the fact that there is empty space between the outer walls of a thermos. Just as houses have the same, this prevents most of the conduction and radiation because the thermal energy will get trapped between the walls. Thank you for reading my response and I hope this helps you improve your article.

Jacob - Canada

17331

Answer

Thank you for the feedback. The lesson does state that a Vacuum Thermos Bottle has no air in between its walls. They are also silvered to reflect heat. I have a separate article on Thermal Insulation that explains home insulation.

I appreciate you helping out to make the lessons better and will check them over with your suggestions.

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Would a Styrofoam container keep ice cream cold?

Question

February 9, 2009

if i follow this article and make a container made out of styrofoam, would i be able to keep ice cream from melting for atleast 20 minutes??

and would wool be a good insulator as well?

Gerald - USA

17242

Answer

You can make a container our of Styrofoam or put a small container inside a larger one (like two jars) and fill in the area between them with Styrofoam or some other insulator. Wool could also be used.

Note that much heat or cold is lost through the cap, so that must also be insulated.

The thickness of the insulating material determines the rate that heat or cold is lost. You would have to experiment to find a sufficient thickness to keep ice cream from melting for 20 minutes.

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Need to keep a can cold for 5 hours

Question

February 28, 2008

I have to build a device that keeps a can cold for 5 hours and that fits into a lunchbox...what would be the best insulator and how should I build it?

Maria - Canada

15451

Answer

See the lesson on Reader Feedback an Questions in both the lesson on Thermos Containers and Thermal Insulation to see what other students have done.

The simplest thing is to wrap the can in insulating material, such as Styrofoam. There is insulating wrap available in some hardware stores.

You could put the can in a jar filled with packing peanuts or other loose material like that.

I hope that helps with your project.

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Should I use newspaper for my thermos?

Question

January 13, 2008

sHOULD I USE A NEWSPAPER FOR MY PROJECT?
P.S SHOULD I USE IT FOR BOTH HOT AND COLD.

SIDRA - Canada

15118

Answer

Look at the Reader Feedback to see what other students are using. Newspaper could work if it is wrapped thick enough. Styrofoam or other foam material is probably better.

Don't forget to insulate the top of your container, but yet be able to open it.

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Should I put shiney aluminum foil in my thermos?

Question

January 12, 2008

Hello,
I am planning to make a thermos for a school project in 3 days. I would like to put the shiny side of aluminum foil in the can, and the dull side on the outside of the can. To keep the heat inside, I would like to paint the shiny aluminum with a thin layer of black paint, and then put some plastic wrap so that the paint doesn't wash away.
Will the plastic wrap absorb some of the heat? Is there anothe clear material that I may use (that is household)that has kenetic energy?

Iris - Canada

15113

Answer

The shiny foil only reflects radiated heat inside a glass thermos. If you are using a can as a container, foil and paint do little. The most important thing is to wrap the can in insulated material. This includes the top and bottom. You don't want a material to absorb the heat. Rather, it must insulate and prevent heat or cold loss.

You can use bubble wrap, Styrofoam, or even layers of newspaper. See our Reader Feedback in the lessons on Thermos Container and Thermal Insulation to see what other students have done.

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Have to insulate a chocolate bar

Question

December 4, 2007

I have to insulate a chocolate bar so that it does not melt in the sun at about 30 degrees Celsius for about an hour. I was thinking of putting the chocolate bar in a plastic bottle, filling it with Styrofoam balls, then wrapping it in layers of newspaper, and lastly, wrap it in foil with the shiny side out. Is this OK? Is there any way I can do it better?

Thanks. I really appreciate it, your website is AMAZING!!!

Sibonay - Singapore

14903

Answer

Yes, your technique should work. Just to make sure, cool your bottle and filling before you put in the chocolate bar. No sense in putting it in a warm container.

Because of the shape of the chocolate bar, it might be better to use a rectangular container, so that you don’t have an edge of the bar too close to the outside.

See our sections on Thermal Insulation and Thermos Container for information on the subject. Also look at the Reader Feedback to see how other students made their thermos.

http://www.school-for-champions.com/science/thermal_insulation.htm

http://www.school-for-champions.com/science/thermos.htm

Best wishes with your experiment.

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Is a thermos made in China safe to use?

Question

November 24, 2007

Is there a possiblility that some thermos bottles made in China are made from a materials that are unhealthy or poisonous?
Can we assume that all the thermos bottles are safe to use?

Gabriela - USA

14835

Answer

Most thermos bottles have a glass core. You can look inside to see a silvery looking glass. Only glass comes in contact with the food or drink, so that would be safe. The silvering should be on the other side of the glass.

A stainless steel thermos is probably also safe to use, since they would never add lead to the steel.

On the other hand, I would avoid having food come into contact with anything painted or with a Teflon-type material that was made in China. This is especially true for objects you heat in the container, like a pot. The paint made have lead in it and heating can cause material to get into your food.

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Needs to keep water warm for 6 hours

Question

May 31, 2007

ok. my project is to make a insulator. I know everything of what to do. however our project is to keep the boiling water warm for 6 hours without a lid. There is no limit of how big the bottle, jar, or can is. can tou give me the best ideas.

John - Canada

13856

Answer

Boiling water is at 212 F or 100 C. But who knows what warm is? Is it just warm to the touch? You should ask your teacher to clarify what temperature it should be.

Use a larger plastic or glass jar. The more insulation you wrap around the jar the better, but you don't want to overdo it.

You need to be able to test your thermos by measuring the temperature of the water after a few hours. The problem with taking off a cover or lid is that you lose a lot of heat. So it might be good to have a small hole that you can unplug and slide in a thermometer. Or even have a thermometer stuck in all the while.

Make a thermos with some insulation. Put in hot water and put it in the refrigerator freezer for an hour. If the water is still warm, you can then test it at room temperature for 6 hours. But if the water is cool or cold, you need to add more insulation and make sure there are no leaks, like by your lid.

I hope that helps. Best wishes in your project.

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