Ch 10 Heat pgs. 357 - 386
Temperature Adding or removing energy usually changes temperature Temperature is proportional to the kinetic energy of atoms and molecules
Temperature Temperature is meaningful only when it is stable Thermal Equilibrium – the state when two objects in physical contact have identical temperatures Matter expands as temperature increases (thermal expansion)
Measuring Temperature Thermometers Most make use of a change in the volume of a gas or liquid Most are thin glass tubes containing mercury, colored alcohol, or colored mineral spirits
Measuring Temperature Calibrating thermometers requires fixed temperatures Ice point of water – thermometer in equilibrium with a mixture of ice and water at 1 atm Steam point of water – thermometer in equilibrium with a mixture of steam and water at 1 atm
Temperature Conversion Temperature in Fahrenheit (TF ) Units are °F Temperature in Celsius (TC) Units are °C
Temperature Conversion Temperature in Celsius (TC) Units are °C Temperature in Kelvin (T) Units are K
Heat and Energy Heat – the energy transferred between objects because of a difference in their temperatures Always moves from the object with the higher temperature to the object with the lower temperature
Heat and Energy
Heat and Energy The transfer of energy as heat alters an object’s temperature Energy transfer depends on the difference of temperature of the two objects
Heat and Energy Greater temperature difference = greater amount of energy transferred At thermal equilibrium, the net energy exchanged is zero
Heat (Q) Heat (Q) has units of energy
Internal Energy (U) The energy of a substance due to atomic motion Units are Joules (J)
Internal Energy (U) Internal energy can be changed through work (friction) The energy required to overcome friction is transformed into internal energy Internal energy can also be changed by deforming a solid’s structure Stretching a rubber band or bending metal
Conservation of Energy ½ mvi2 + mghi = ½ mvf2 + mghf + ΔU
A device used to demonstrate energy conservation is shown A device used to demonstrate energy conservation is shown. If a total mass of 11.5 kg falls 1.3 m and all of the mechanical energy is converted to internal energy, by how much will the internal energy of the water increase? (Assume no energy is transferred to or from the surroundings.)