The aim of this experiment is to find out if a steaming cup of coffee stays warm longer when leaving it untouched, or pouring cold milk into it Theory Physics informs us that large quantities of liquid take longer to cool than smaller quantities. Since there are more molecules in a larger quantity of liquid it may take longer to heat, but once the molecules are heated they take longer to cool down than a smaller quantity of water. Therefore I expect the beaker where the milk has been added straight away to have a higher temperature
Procedure 1. First of all the coffee has to be made. Pour some water in the large beaker and heat it using the Bunsen burner. Once the water is boiling sprinkle the coffee powder into the beaker and stir it until the coffee is made. 2. Now pour equal amounts of coffee into the beakers A and B, and place a thermometer in each beaker. Set the stopwatch on zero and start recording the time. Record the temperature of each beaker.
3. Pour the milk into beaker A and stir the liquids for a short amount of time. 4. Now let a member of your group walk across the laboratory and open the door. Obtain the time duration of this procedure. 5. As soon as the team member returns to the experiment site pour the same amount of cold milk into Beaker B. record the temperatures of both beakers after stirring beaker B for a short time.
6. Now repeat this experiment, but change the amount of time spent going to the door and back. Also change the amount of milk and water used. Record your results appropriately. Smallest division for measuring liquids (water, milk) = 0.1 ?C Error = 0.1 ? 0.5 = 0.05 ?C Difference between Beaker A and Beaker B: The average difference = A – B = 51?C – 49.50?C = 1.50?C. Error: 0.05?C + 0.05?C = 0.1?C Therefore difference = 1.5 ?0.1?C
As always the apparatus was set up with great care, and I ensured that the thermometers were not heated or cooled before being used. The only major error that may have occurred is the parallax error. This may have happened during the taking down of readings from the thermometers, although great care was taken to avoid this.
As the table of results shows; the beaker in which the milk was poured right after the coffee was added (beaker A), meaning it contained more liquid during the procedure of going up to the door and back, did indeed stay warmer. Beaker A was, on average, 1.50?C warmer than Beaker B. This supports my expectations and I conclude the experiment as being successful. Therefore the best option would be to pour the milk before attending to the door, especially if it would take a longer period of time to deal with the person at the door.