Introduction:

The rate at which an object cools (i.e. how quickly its temperature decreases) depends upon several factors, including:

  • Surface area
  • Volume
  • Type of insulation
  • Temperature difference with the surroundings

For this investigation, the effect of the temperature of water upon the rate of cooling will be investigated. The temperature-drop over 5 minutes (600 seconds) will be measured for 200ml of water at different start temperatures. The average rate of cooling can then be found by:

avg-rate-of-cooling

Apparatus:cooling

  • digital stopwatch
  • 250ml beaker
  • rubber bung
  • thermometer
  • bunsen burner
  • tripod
  • gauze
  • retort stand and clamp
  • goggles

Control Variables:

  • Volume of water used: 150ml
  • Size of beaker (i.e. constant surface area): 250ml
  • Time interval of cooling: 5.0 minutes (600 seconds)
  • Temperature of the room: 21°C

Method:

  • Fill an empty beaker with exactly 150ml of water (check side-scale of beaker)
  • Set up apparatus as shown above. Ensure the thermometer is about 2cm above the bottom of the beaker.
  • Light the bunsen burner and put on a blue flame. Heat up the water.
  • When the temperature on the thermometer has reached 90°C, immediately switch off the burner.
  • Start the stopwatch and time for 5.0 minutes.
  • Read the thermometer value at the 5.0 minute mark.
  • Before repeating the experiment, check the level of water is still 150ml (some may have evaporated) and add more water if required.
  • For different start temperatures, repeat steps 3-7 but turn off the burner at the desired temperature.

Results:

Start Temperature of Water (°C) Temperature after 5min (°C) Drop in Temperature

(°C)

Average Rate of Cooling x 1000 (°C/s)
80 70 10 17
75 66 9 15
70 62 8 13
65 59 6 10
60 55 5 8

 

cooling-rate-graph

Conclusion:

There is a strong correlation between the average rate of cooling and the start temperature: the greater the start temperature, the faster the average rate of cooling.

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25 Comments on "Temperature of Hot Water and Cooling Rate Lab"

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guest
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risk assessment?

brian
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WOWWW!! best link ever.

Georgia
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This is the best link EVER!!!!!!!!!

jack
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helpful ._.

Alisha M.
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this is very helpful thanks!

Guest
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hi, nice work! Useful for the CAU

student
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5 mins is not 600 seconds

Angie
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How 5 minutes can be 600 sec ? I think it is 300 sec therefore the average rate of cooling is wrong.

Henry P.
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Perfect, thanks

guest
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this was a real nice bit of work gotta love it

Nikesh C.
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thanks! this was very helpful.

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