Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine

Quiz Temperature T(K) = T( o C) Three laws of thermodynamics Absolute zero Entropy Specific heat capacity Q = c m ∆T Properties of ice and water Thermal expansion

Entropy Entropy is the measure of how energy spreads to disorder in a system

Entropy Entropy is a measure of the "multiplicity" associated with the state of the objects. If a given state can be accomplished in many more ways, then it is more probable than one which can be accomplished in only a few ways.

Specific Heat Capacity Specific heat capacity of any substance is defined as the quantity of heat required to change the temperature of a unit mass of the substance by 1 o C

For example The filling of hot apple pie can be very hot while the crust is not. The filling and crust have different specific heat capacities. It takes a longer time to heat a pot of water to its boiling temperature than to heat an equal mass of iron to the same temperature.

Water Water can absorb a great amount of heat for small increases in temperature That is why water is useful in cooling systems

Q = c m ∆T Q is the quantity of heat c is the specific heat of the substance m is the mass ∆T is the temperature change specific heat of water is 1.0 cal/(g ∙ o C) or J /(g ∙ o C)

Example You mix 100 g of water at 25 o C with 75 g of water at 40 o C What is the final temperature? Heat gained by cool water = Heat lost by warm water c m 1 ∆T 1 = c m 2 ∆T 2 c (100 g)(T-25) = c (75g) (40-T) 100T – 2500 = 3000 – 75T T = 31.4 o C

Proton Alpha Helix

Temperature reflects the average total kinetic energy of the particles Heat is the transfer of thermal energy; it flows from regions of high temperature to regions of low temperature. Thermal energy is stored as kinetic energy and, in molecules and solids, also as potential energy in the modes of vibration

Thermal Expansion As the temperature of a substance increases, its molecules move faster and move farther apart Most substances expand when heated and contract when cooled

Ice is the only known non-metallic substance to expand when it freezes.

0 o C 1 o C 2 o C 3 o C 4 o C

Any Questions?