Help me come up with a better test and I'll post the results?

Question

I want to do an experiment that clearly proves that when you have a limited amount of a heat absorbing materiel (like water), that for the maximum cooling efficiency, it's better to wait before using it to cool the hot object or whatever it is. I did this little one yesterday:


I took two glass beakers with 200mL of 99C water in each. I added 40mL of 25C water to each at separate times. Here are the results:

A (Room temp water added at 1:00 min)
B (Room temp water added at 9:00 min)

Minute [ Temp A(C) / Temp B(C) ]

0 [ 99 / 99 ]
1 [ 87** / 95 ]
2 [ 85 / 91 ]
3 [ 83 / 88 ]
4 [ 81 / 86 ]
5 [ 79 / 84 ]
6 [ 78 / 82 ]
7 [ 77 / 80 ]
8 [ 76 / 79 ]
9 [ 75 / 70**]
10 [ 74 / 69 ]

**-room temp water added

I need help brainstorming ideas for a better test.

Gnik: Losses to ambient are the whole point of the test. The room was 25C.

The two 40mL beakers were in equilibrium with their surroundings. I filled them from an open container of water that had been sitting there for over 24 hours.

Answer 1

This test seems adequate, but the effect of greater cooling is not due to the later addition of water, but the fact that the hot water cools faster. You are demonstrating Newton's law of cooling, that dT/dt is proportional to deltaT between the hot object and the thermal reservoir around it. Since the temperatures are still fairly equal, you'll notice that upon the addition of the water, you get a similar ~9C drop in both cases. This drop will only depend on the initial temperatures and masses of water, and only indirectly on time, since time is changing the water temperature in both beakers.

Answer 2

There are several independent and variable cooling processes taking place. Each of the four beakers is cooling independently.
Then three, then two.
For there to be proof or denial of your idea, the beakers must be all exceptionally well insulated to remove those variables.

Answer 3

Would it matter since it takes the same calories to heat and cool water Vs is your control was hotter or cooler...just more or less calories...I might just not understand what you want...