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I am taking a course on thermodynamics. I have a question from my text(halliday & resnick,physics-1). They asked me to measure temperature of an ant or an insect or a small body,like a small robot. If I build a thin thermometer then it is probable that surface tension would have greater influence than thermal expansion. Then How can I measure the temperature of an ant?

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Insert that in the mouth of Ant.. :) –  Sachin Shekhar Dec 21 '12 at 4:03
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Or in the other end of the ant :-) –  John Rennie Dec 21 '12 at 7:58
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3 Answers

up vote 7 down vote accepted

Alternatively I would look around the lab for an infrared thermometer. There exist in the market close focus ones that go down to 6mm in close focus option ( so as not to advertise, google space accurate infrared thermometers microscopes where I found the number in a one of the first hits).

I would choose a large ant, or attract more by a spot of honey and measure their average temperature.

Edit I think finally the answer is like the egg of Colombus,or the Gordian knot) as we say in Greece. Think, do ants have temperature regulator mechanisms?

The egg of Colombus parable : Colombus was sitting at a table and a bowl of boiled eggs came in. All the men around the table played a game of trying to balance the eggs on their narrow end. Colombus said: "what nonsence". and he sat the egg down on its end, breaking it and solving the geometry. :)

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I prefer this answer to Raindrop's purely on grounds of practicality, but I suppose there is an objection that you'd be measuring the surface temperature of the ant, and if chitin is a good insulator that may be quite different from the core temperature. –  John Rennie Dec 21 '12 at 8:05
    
@JohnRennie did you read my edit? Think a bit about it. –  anna v Dec 21 '12 at 12:55
    
Ants must have a higher temperature than their environment because they metabolise carbohydrates in an exothermic reaction. However I agree with you that their core temperature isn't likely to be a lot higher than their environment. –  John Rennie Dec 21 '12 at 13:13
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Ants are cold blooded. Therefore the temperature of an ant is the ambient temperature in which it exists at the moment. If the ant is in an environment of variable temperature and is moving around, then it has no temperature in the thermodynamic sense. If it is in a region of uniform temperature, then that is its temperature.

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it is not important that,the particle should be an ant.I want to say that it is an small particle......with small mass. –  Arafat Dec 22 '12 at 5:03
    
I hinted at this in the edit in my answer because I believed it was a homework and did not want to give a direct answer. Alive things manage to have some temperature over the ambience when moving and digesting , as @JohnRennie observed in his comment due to chemical reactions. So it is important whether something is inanimate or alive. The temperature of small inanimate things is the same as the environment except if they are just out of the sun, or out of fire or in from the cold. –  anna v Dec 22 '12 at 5:22
    
The key word in the question is "measure". –  Magpie Mar 16 '13 at 20:14
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Put ant in small volume of cold water, maybe 5ml. Measure the final temperature of water using some thermometer and solve for temperature of ant using the thermal equilibrium equations.

$$m_{ant}c_{ant}T_{ant}+m_{water}c_{water}T_{water}=m_{(ant+water)}T_{final}(c_{water}+c_{ant})$$ $$T_{ant}=\frac{m_{(ant+water)}T_{final}(c_{water}+c_{ant})-m_{water}c_{water}T_{water}}{m_{ant}c_{ant}}$$

Note that you need to measure the mass of the ant and water separately before the experiment. Also, choose a volume of water big enough so that you can use your thermometer. To increase precision, choose a temperature of water that is 'more different' than the temperature of the ant, for example choose water that is much cooler than the ant. Also, conduct the experiment in a short time frame to minimize thermal equilibrium with environment.

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How do you determine $c_{ant}$? This is unknown as well, so unless I am missing a point here, you are sacrificing the ant for nothing. I'll have to downvote this answer, until you clarify this issue. Maybe $c_{ant}$ is tabulated? –  Bernhard Dec 21 '12 at 6:36
    
@Bernhard google heat capacity of insects. You could use one found from other insects than ants; be prepared the process of finding it is destructive to the insects. Also those experiments have evidently solved the measurement of temperature problem. –  anna v Dec 21 '12 at 7:14
    
@annav I think you'll get huge error margins in this approach. –  Bernhard Dec 21 '12 at 7:25
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@Bernhard: it's still worth a try though. You could easily measure the specific heat of ants by equilibrating them in water at a known temperature prior to putting them in your experimental cell. –  John Rennie Dec 21 '12 at 8:02
    
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