Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: singh on 12/06/2004 22:01:19
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Hi guys, i need a bit of help, i need to know how much energy is needed to heat 1ml of water to 90 C and sustain it for around 1 to 2 minutes. Just roughly guys so you dont need to take anything else into account. PLease help me in my hour of need!
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Assuming you're starting the water from average room temperature of 25 C, the energy to get to 90 is a simple calculation of mass * specific heat * temp. The energy to hold it at 90 would be equal to the energy it would lose to its surroundings over that period of time, and is a little more difficult to obtain accurately. You might use Newton's law of cooling and derive it for energy instead of temperature.
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Yep- look up the specific heat capactiy of water - its about 4.12 joules per kelvin per gram. If you want to maintain the temperature, use a thermostatically controlled electric heater - they can be calibrated and the energy used can easily be found by considering the measured current and voltage.
"I have great faith in fools; self-confidence my friends call it."
-Edgar Allan Poe
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Well thats this lads homework done... you guys are too nice, look at the title, they didnt even say please...
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Why is some of you so freaked out about helping someone with their homework? It's not like he posted 30 questions and we answered them all, he asked one question that he was obviously having trouble with. I tutor for the chemistry department at my school and this is exactly what we do...someone does their homework and comes in with the problems they have difficulty working out, so we show them how to do it and explain the concepts. Why's that so bad?
He might not say please in the title, but he does in the body text. Read the last sentence.
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quote:
Originally posted by cannabinoid
Why is some of you so freaked out about helping someone with their homework? It's not like he posted 30 questions and we answered them all, he asked one question that he was obviously having trouble with. I tutor for the chemistry department at my school and this is exactly what we do...someone does their homework and comes in with the problems they have difficulty working out, so we show them how to do it and explain the concepts. Why's that so bad?
He might not say please in the title, but he does in the body text. Read the last sentence.
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Firslty it was a flippent joke, not sure if you have taken it the wrong way.
Secondly - If someone works through the problem with the student then i think its great and the more we do it the better, i was making the point (and it has happened with me) that if someone does the calculation for you, then you never actually learn how to do it yourself...
Concerning the please... i had not seen that so i take that back.
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Sorry, took you too seriously. Ah, the dangers of the internet. =P
It's hard to really work through a problem with someone online, so all you can really do is either be vague and general (which usually doesn't help) or just tell them how to do it and explain the concepts as you do so. I chose the latter.
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quote:
Originally posted by cannabinoid
Sorry, took you too seriously. Ah, the dangers of the internet. =P
It's hard to really work through a problem with someone online, so all you can really do is either be vague and general (which usually doesn't help) or just tell them how to do it and explain the concepts as you do so. I chose the latter.
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Thats cool, sorry if you thought i was having a go... yeah the dangers of the net. Almost as dangerous as text messages. It proves how important observing peoples body language or voice tone is when talking!