Newton’s Law of Cooling
According to Newton, "the rate of heat loss of a liquid is directly proportional to the difference in temperature between the liquid and the surroundings".
To verify the law, take hot water in a calorimeter and note the temperature and time of the water during cooling until temperature is few degree (100C) above the temperature. Now plot a graph between temperature and time. If θ is the room temperature, the excess temperature is θ - θ0 at a temperature θ, then, at various temperatures, tangents are drawn to the curve, and the slope of tangent gives the rate of fall of temperature.
Rate of fall = AB/BC = (θ2 – θ1)/(t2 – t1)
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