Ask-a-Physicist by Topic

Thermodynamics & Heat

Why does hot air rise?

If air is heated and its starts to go towards the space, what is the reason for this? Do you think the air molecules will get accelerated and because of this they will resist Earth’s gravitational force?


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Phases of Matter

My 9 year old wants to know if a single atom exists in a certain state of matter — or must it be associated with other atoms in order to define a state?


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Helium Balloon in an accelerating car

Under acceleration, a helium-filled balloon inside of a car will jump forward in the direction of acceleration. I have been searching for the reason why with no definitive results. This is the dilemma: An acquaintance of mine, who has a degree from Johns Hopkins is attempting to argue for some magical force that drives the balloon forward, also that it has something to do with gravity.


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Frying Pan Physics

A friend of mine claims to notice that when he takes a hot frying pan (with a warm, insulating handle), and pours cold water into it, the handle seems to get hotter. He thinks it is because the handle is less insulating than the air, thus the path of least resistance is through the handle.

This would make sense to me when you take the pan off of the heat, but he claims that it isn't until the water hits it that the handle gets significantly hotter. If this is true, what does the water have to do with it? If anything, wouldn't the water become the path of least resistance, and heat would move from the metal to the water, and from the handle to the air?


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glasshouse How can 'greenhouse' gases transfer heat to the earth's surface? Doesn't that mean energy is being transferred from something low energy to something at a higher energy? Does this theory violate thermodynamics law?
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match

Why does a flame from a fire or match go up?


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water_and_ice-tn

Does an ice cube have heat energy (kinetic energy)? If so, does a glass of water with ice have more heat energy than a glass of water without ice?


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ice cubes

Why do ice cubes sometimes stick to your skin?


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insulation How does house insulation work? — JB
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oven What are the advantages and disadvantages of convection ovens over standard ovens? – KK, Rochester, NY
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warming What does physics have to do with global warming? — ML, New York
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humidity Why does humidity affect temperature? - H, Heyworth, IL
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music How does temperature affect the sound of a flute? — S
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farmhouse Why does my older farmhouse feel warmer and seemingly easier to heat the colder it gets outside? I live 20 minutes north of Maine, which should give you an idea what kind of winter temperatures we have to endure. - JS, Greenfield, New Brunswick, Canada
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balloons Why do mylar balloons lose or seem to lose helium when taken outside in the cold and blow back up or seem to blow back up when you take them back in where it is warm? — TS, Alabama
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bulbs We're confused about the difference between fluorescent and halogen bulbs. Fluorescent bulbs are classified as hazardous waste because they contain mercury. Do halogen bulbs also contain mercury? - LR and APM, Washington, DC
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candle What causes the smoke produced when you extinguish a candle flame?— SB, Plymouth, England
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flame Which color is hotter, red or violet? — LL, Falls Church, Virginia
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