A law is a principle that describes a consistent relationship or pattern observed in nature. It is based on repeated experimental evidence and remains universally valid under specified conditions. Laws explain natural phenomena and predict outcomes without exceptions or deviations.
Thermal properties of matter deal with how matter responds to changes in temperature. This includes thermal expansion heat conduction convection and radiation. Matter expands when heated and contracts when cooled. The behavior of gases liquids and solids is studied in terms of their thermal properties to understand energy transfer and phase changes.
Newton’s Law of Cooling: Newton’s law of cooling provides the rate at which the temperature of a body changes with respect to time in proportion to the difference between its temperature and ambient temperature, while the difference should not be significantly large.
Mathematical Formulation: dT/dt = -k(T-T∞) In the above relation: T – Temperature of body at time ‘t’ T∞ Ambient temperature or Temperature of surrounding media k Positive coefficient of proportionality (cooling constant)
– dT/dt = rate of change of temperature with respect to time
Experimentally Verification of Newton’s Law of Cooling:
1. Materials Required: Hot water, calorimeter, thermometer, stopwatch, and a controlled room for a stable ambient temperature.
2. Procedure:
– Heat water to a certain temperature.
– Pour it into a calorimeter and record the initial temperature T₀.
– Put the calorimeter in a room whose ambient temperature is kept constant at T∞.
– Use a thermometer to measure the water temperature at equal intervals of time and record the readings.
3. Observation:
– Plot a graph of ln(T – T∞) vs. time.
– If the graph is a straight line with a negative slope, it confirms the law.
4. Conclusion:
– The slope of the line will be negative and will be proportional to the cooling constant k.
This experiment verifies Newton’s law of cooling.
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