A temperature question

[JABBARA]

Hi everybody,

I am sure there is scienific explanation for this:

Today the temperature is 20 degrees Celcius, and 2 weeks later it is expected to be two times warmer; around 40 degrees Celcius.

Now answer this:
Today the temperature is 0 degrees Celcius, and 2 weeks later it is expected to be two times warmer; around how many degrees?

Thanks

[TheOddOne]

Today the temperature is 20 degrees Celcius, and 2 weeks later it is expected to be two times warmer; around 40 degrees Celcius.

WRONG!

A temp 2 times warmer than 20 deg Celcius is actually

(273 + 20) x 2 - 273 = 586 - 273 = 313 deg C

A temp 2 times warmer than 0 deg Celcius is actually

(273 + 0) x 2 - 273 = 273 deg Celcius.

Explanation.

Temp should actually be measured from absolute zero and is properly expressed in degrees Kelvin. The approximate freezing point of water is 273 deg Kelvin. We use a couple of scales, Farenheit and Celcius, to help keep numbers sensible within our daily experince of the world around us. They should not be confused with proper measurement of absolute values of energy.

Cheers,

TheOddOne

[italianjon]

Interesting statement.

You could go back to the Kelvin Scale. That way 0K is really a zero temperature.

As zero celcius is 273.15K, and it follows the same increments as celcius, so therefore 20 celcius is 293.15K.

Double that is 586.3K, which is equivalent to 313.15 Celcius.

I think the question is very ambiguous at best.

Do not think temperature is linear to the amount of energy stored. So it may be something wired like 25 Celcius... I'll have to dig out university notes on thermodynamics!

L8rs

J

[palgia]

Do not think temperature is linear to the amount of energy stored.

Last time I checked, temperature was linear with the average kinetic energy of the molecles in a substance. In fact, I was taught temperature IS a measure of the average (mean) kinetic energy of the molecules in a substance. The amount of mass the substance has would then determine the "total energy stored".
Obviously you have reference either Kelvin or Rankin, as TheOddOne pointed out.

I might be wrong though.... GCSE physics was a LONG time back:}

I agree that the question is very ambiguous. As a meteorologist, I've never heard of the temperature being described as "twice as warm/cold"...:uhoh:

regards,

palgia

[alexban]

he,he you fall for it...
the problem is this:it's not a mathematical question,it's physical one.
If you study the water phase diagram ,the tripple point is 273.15K.
It is a unique temperature value,not some math figures. This is 0 C. This value can not be multiplied,physically speaking.It's like you'll try to divide by 0 in maths.
The only value used in calculations regarding temperature modifications is the Delta T.
20C is 273+20 K
Duble than this is 273 +(20*2)=313 K= 40C
The answer that we've expected.
It's normal physics.
We should not multiply the origin,only the deltaT.I'll give you another example:
suppose today I walk 10m from A to B.Tomorrow I'll walk another 10m,so double distance from the start.
Now suppose point A is 100m from the origin X.
The distance that I've walked in the first day is 10m or 110m? See my point? Then the double is 20m or 220m? If it's 220m,then by deducting 100m you'll find the value in the first scale used? WRONG. (compare to the Oddone example)
That's it.You should not multiply the origin ,and also changing scales used during calculations can be very tricky for inexperienced people.
Brgds...
Alex

[jb5000]

Alexban,

I'm not sure you're reasoning is completely correct.

How 'hot' something is must be in reference to absolute zero. (-273 oC). In your distance example you are choosing an arbitrary origin, which is different to the Kelvin temperature scale, as this origin is defined and absolute.

The confusion arises by introducing an arbitrary origin, which is as you say, the triple point of water. However, it is perfectly possible to have chosen different reference points (e.g. Farenheit where 100F is body temperature, give or take a few degrees).

E.g. say it was 80 oF on a summers day (approximately 27 oC), if you were wondering what it would be like to be twice as hot would you say that it would be 160 oF (71 oC) or 54 oC (130 oF).

As you can see the choice of origin vastly affects the result.

Therefore, the only true sense of 'twice as hot' must be in reference to absolute zero. Twice as hot in this sense means that particles have twice as much kinetic energy as they did before. (As absolute zero implies zero kinetic energy).

James

[JABBARA]

Thank you all, I ve got my answer anyway.

And thank you PPRUNE, because you let me meet all these wise guys.:ok:

[BOAC]

OK - into the ring goes 64deg F??

[northwing]

Place one foot in a bucket of ice. Place the other one in a bucket of boiling water. On average you are comfortable?