Quiz 1 8:30-8:50am TODAY Closed book 7A Final March 18, Tuesday 10:30am-12:30pm No makeup final/quiz Chapter 0 = introductory material at the beginning of the text Lecture slides at by ~ 5pm Tuesdays

Due to Monday holiday (1/21), 1/17 Thursday DL Section 1,3,4 cancelled (DL section 7, 10 meet as normal) 1/18 Friday DL Section 2,5,6 cancelled Next lecture January 22 Quiz 2 will cover the material from today’s lecture and DL 3 this week, excluding FNTs.

ice cream recipes “A Little House in the Big Woods” way A VERY quick way

0 0 C Ice-cube Water An ice-cube sits in a bath of water. Water and ice can exchange heat with each other but not with the environment. What is the direction of heat transfer? A. From ice-cube to water B. From water to ice-cube C. Impossible to tell D. Neither of above

Heat If the two objects are at the same temperature, no heat flows between them. Let us move away from these colloquial terms heat and cool. We introduce a scientific use of the term heat. Low tempHigh temp Heat Heat (Starting definition (to be revised much later)) transfer of energy that takes place from a hot object to a cold one because the objects are at different temperatures. Energy leaves hot objects in the form of heat Energy enters cold objects in the form of heat

0 0 C An ice-cube sits in a bath of water. Water and ice can exchange heat with each other but not with the environment. What is the direction of heat transfer? A. From ice-cube to water B. From water to ice-cube C. Impossible to tell Ice-cube Water D. Neither of above Ice-cube and water are in thermal equilibrium

Thermal equilibrium If the two objects are at the same temperature, no heat flows between them. in thermal equilibrium A system in thermal equilibrium is a system whose temperature is not changing in time. T final Energy leaves hot objects in the form of heat Energy enters cold objects in the form of heat Low tempHigh temp

Reaching Thermal equilibrium A cup of hot coffee left in a room… A thermometer Cold beer It can take some time for things to reach thermal equilibrium with its environment. ~ what is happening at microscopic level? => more to come when we cover Particle models of thermal energy

C = [C] = J/K Slowing it down Coffee cup: ceramic material A thermometer Tip:metal Body:glass, plastic Beer glass: glass Heat capacity of substances: A measure of the amount of energy required to increase the temperature of the substance a certain amount

Heat capacity vs Specific heat capacity Porcelain 1.1kJ/kgK Tip:metal (Silver 0.24kJ/kgK) Body: plastic ~ 1.2kJ/kgK Glass 0.84kJ/kgK Heat capacity is an extensive property: Heat capacity of a pint glass is greater than heat capacity of a 3 oz sampler glass (i.e. made of same material, more glass material used in a pint glass) Specific heat capacity is an intensive property: the amount of energy per unit mass/unit mole required to increase the temperature of the substance by one degree Kelvin Heat capacity is an extensive property: 2kg of water will have twice the heat capacity of 1kg water Specific heat capacity is an intensive property: Specific heat capacity only depends on the substance

C = [C] = J/K Heat capacity vs Specific heat capacity Heat capacity of substances: A measure of the amount of energy required to increase the temperature of the substance a certain amount Specific heat capacity : the amount of energy per unit mass/unit mole required to increase the temperature of the substance by one degree Kelvin [C p ] = kJ/kgK = kJ/moleK

A note on temperatures Kelvin: the standard for scientific use. Increasing the temperature by 1 K = Increasing the temperature by 1 0 C Celsius/Centigrade Same as Kelvin except 0 in a different place Fahrenheit Smaller unit of temperature

Heat capacity in Three-phase Model of Matter Temperature (K) Energy added (J) solid liquid gas ∆T ∆E C = [C] = J/K

Heat capacity in Three-phase Model of Matter Temperature (K) Energy added (J) solid liquid gas TbTb ∆E C = [C] = J/K

Temperature (K) Energy added (J) solid liquid gas TbTb ∆E Heat of vaporazation : ∆H the amount of energy per unit mass/unit mole required for a substance to change its phase from liquid to gas or vice versa

Temperature (K) Energy added (J) solid liquid gas TmTm ∆E Heat of melting : ∆H the amount of energy per unit mass/unit mole required for a substance to change its phase from solid to liquid or vice versa

Temperature (K) Energy added (J) solid liquid gas TmTm ∆E Typically, ∆H v >> ∆H m e.g. It takes 6 times more energy to vaporize 1kg of water than to melt the same amount of ice TbTb ∆E

Example 0.1 kg of water at 20 0 C is placed in contact with a 2 kg block of (solid) silver at C. What will happen after a long time? You may neglect heat that it lost to the surrounding air in the room. Note: C silver = 233J/kgK, C water = 4200 J/kgK, T m Silver = C Final state of water : L? L+G? G? Final state of silver : S

What is the final state of water? 0.1 kg of water at 20 0 C is placed in contact with a 2 kg block of (solid) silver at C. What will happen after a long time? You may neglect heat that it lost to the surrounding air in the room. Note: C silver = 233J/kgK, C water = 4200 J/kgK, T m Silver = C How much energy is required to raise the temperature of water to 100 °C?

What is the final state of water? 0.1 kg of water at 20 0 C is placed in contact with a 2 kg block of (solid) silver at C. What will happen after a long time? You may neglect heat that it lost to the surrounding air in the room. Note: C silver = 233J/kgK, C water = 4200 J/kgK, T m Silver = C mc water ∆T water = mc water (T f w - T i w )=(0.1kg)(4200J/kgK)(100°C-20 °C) = 33.6kJ How much energy is required to raise the temperature of water to 100 °C?

What is the final state of water? 0.1 kg of water at 20 0 C is placed in contact with a 2 kg block of (solid) silver at C. What will happen after a long time? You may neglect heat that it lost to the surrounding air in the room. Note: C silver = 233J/kgK, C water = 4200 J/kgK, T m Silver = C mc water ∆T water = mc water (T f w - T i w )=(0.1kg)(4200J/kgK)(100°C-20 °C) = 33.6kJ How much energy is required to raise the temperature of water to 100 °C? mc silver ∆T silver = mc water (T f s - T i s )=(2kg)(233J/kgK)(100°C-200 °C) = kJ How much energy needs to be removed to decrease the temperature of silver to 100 °C?

Water will reach its phase transition temperature. Will all the water vaporize? 0.1 kg of water at 20 0 C is placed in contact with a 2 kg block of (solid) silver at C. What will happen after a long time? You may neglect heat that it lost to the surrounding air in the room. Note: C silver = 233J/kgK, C water = 4200 J/kgK, H water = 2257 kJ/kg, TmSilver = C m water ∆ H vap w = (0.1kg)(2257kJ/kg) = 225.7kJ How much energy is required to vaporize all the water? Will all the water vaporize?

Water will reach its phase transition temperature. Will all the water vaporize? 0.1 kg of water at 20 0 C is placed in contact with a 2 kg block of (solid) silver at C. What will happen after a long time? You may neglect heat that it lost to the surrounding air in the room. Note: C silver = 233J/kgK, C water = 4200 J/kgK, H water = 2257 kJ/kg, TmSilver = C m water ∆ H vap w = (0.1kg)(2257kJ/kg) = 225.7kJ How much energy is required to vaporize all the water? Will all the water vaporize? No

E bond, water E bond, silver E thermal, water E thermal, silver ? ? ?? Write out all the possible energy systems

E bond, water E bond, silver E thermal, water E thermal, silver ? We know that the water heats up to C and start vaporizing while silver cools to C [+] [-] ∆E th S + ∆ E th W + ∆ E b W = 0 [+]

How much water vaporized? When heat stops flowing, both silver and water are at C. Water is in the mixed phase, silver remains solid. [+] [-] ∆E th S + ∆ E th W + ∆ E b W = 0 [+] mc silver ∆T silver + mc water ∆T water + m water that vaporized ∆ H vap w = kJ kJ + m water that vaporized ∆ H vap w = 0

Example 1 kg of water at 20 0 C is placed in contact with a 2 kg block of (solid) silver at 80 0 C. What will happen after a long time? You may neglect heat that it lost to the surrounding air in the room. Note: C silver = 233J/kgK, C water = 4200 J/kgK, T m Silver = C Final state of water : L? L+G? G? Final state of silver : S

Closed Book Make sure above boxes are filled!