 Thermodynamics  “Thermo” = Study of heat  “dynamics” = Movement of that heat between objects  Thermometers  Measure temperature based on physical properties Mercury based thermometers expand at a predictable rate with temperature Scale of the thermometer measures the amount of expansion

 Temperature scales  Kelvin (K), Celsius (C), and Fahrenheit (F) Temperature values are different on each scale Comfortable indoor room temperature  68° F; 20° C; K Water freezes at 0°C; 32°F; K  There are 100 degrees between the freezing & boiling points of water on the Celsius scale, and 100 Kelvins between the freezing and boiling on the Kelvin scale Units of these two scales are equal Unit of Celsius = Unit of Kelvin

Kelvin temperature

 T K = T C  T C = (5/9)(T F – 32)  T K = Kelvin Temperature  T C = Celsius Temperature  T F = Fahrenheit Temperature

Converting from a Celsius to a Fahrenheit Temperature A time and temperature sign on a bank indicates that the outdoor temperature is o C. Find the corresponding temperature on the Fahrenheit scale. Degrees below ice point ice point

 The lowest temperature any material could theoretically reach  As cold as it can get!  Reference point at which molecules are in their minimum energy state 0 K ( ° C; ° F)

 Thermal energy that flows from one object to another due to a temperature difference  Energy flows from a higher-temperature object to a lower- temperature object because of the difference in temperatures. Example: In an oven, heat flows from the oven coils to the air molecules, warming them up, and then to the bread, warming it as well  Not a property of an object  Represented by the letter Q  SI Unit = Joules (J)

Internal Energy: Energy associated with the molecules and atoms that make up a system Heat flows from hot to cold- originating from the internal energy of the hot substance. It is not correct to say that a substance contains heat.

 Endothermic Processes  Absorb heat from the surrounding area(s)  Cooling effect on the environment  Exothermic Processes  Release heat into the surrounding area(s)  System becomes cooler  Environment becomes warmer

* Farmers farm oranges in the winter (Oranges could freeze!) * Farmer’s Prevention: - Pour water on the oranges  letting the water freeze instead! - Freezing gives off a lot of heat. So, when the water freezes, it gives the heat to the oranges - Freezing  Exothermic  The orange absorbs the heat from the water as the freezing occurs

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 If objects A and B are in thermal equilibrium, and objects B and C are in thermal equilibrium, then A and C will be in equilibrium as well

 Thermal Expansion  Increase in the length or volume of a material due to a change in its temperature Different materials expand at different rates

 Thermal Linear Expansion of a Solid  Length an object changes when its temperature changes Measured along one dimension  Coefficient of linear expansion, is a constant, that specifies how much a given material expands with a change in temperature Represented by greek letter alpha (α)  Linear Expansion Equation ΔL = L i α ΔT L = Length α = Coefficient of linear expansion ΔT = Change in temperature (K or °C)

THE BIMETALLIC STRIP

NORMAL SOLIDS

The Buckling of a Sidewalk A concrete sidewalk is constructed between two buildings on a day when the temperature is 25 o C. As the temperature rises to 38 o C, the slabs expand, but no space is provided for thermal expansion. Determine the distance y in part (b) of the drawing.

 Thermal expansion of water  Above 4°C, water contracts and sinks as it cools You may have experienced this effect if you have jumped into a lake The water is colder the deeper you go  This chilling and sinking of the top layer continues until the lake is 4° C throughout  From 4°C to 0°C, water expands and stays on top  At 0°C, water turns into ice and floats (less dense) ** Crucial for the survival of aquatic life **

Expansion of Water

 Volume of an object changes when its temperature changes Every substance has a coefficient of volume expansion (β)  varies by material  ΔV = V i βΔT V = Volume Β = Coefficient of volume expansion  ΔT = Change in temperature  Β ~ 3α

An Automobile Radiator A small plastic container, called the coolant reservoir, catches the radiator fluid that overflows when an automobile engine becomes hot. The radiator is made of copper and the coolant has an expansion coefficient of 4.0x10 -4 (C o ) -1. If the radiator is filled to its 15-quart capacity when the engine is cold (6 o C), how much overflow will spill into the reservoir when the coolant reaches its operating temperature (92 o C)?

 Property of a material  A constant that tells how much the temperature of a mass of material changes when a particular amount of heat is transferred A material with a large specific heat requires more heat per kilogram to a produce a given change in temperature than one with a smaller specific heat

Q = cmΔT Q = Heat (J or calories) Q = Negative, heat energy is removed Q = Positive, heat energy is added c = Specific heat (J/kg x K) or (cal/g°C) m = mass ΔT = Temperature change in C° or K (ΔT = T f – T i )

A Jogger In a half-hour, a 65-kg jogger can generate 8.0x10 5 J of heat. This heat is removed from the body by a variety of means, including the body’s own temperature-regulating mechanisms. If the heat were not removed, how much would the body temperature increase?

CALORIMETRY If there is no heat loss to the surroundings, the heat lost by the hotter object equals the heat gained by the cooler ones.

Measuring Specific Heat Capacity The calorimeter is made of 0.15 kg of aluminum and contains 0.20 kg of water. Initially, the water and cup have the same temperature of 18.0 o C. A kg mass of unknown material is heated to a temperature of 97.0 o C and then added to the water. After thermal equilibrium is reached, the temperature of the water, the cup, and the material is 22.0 o C. Ignoring the small amount of heat gained by the thermometer, find the specific heat capacity of the unknown material.

 A constant that tells how much the temperature of a particular number of moles of a material changes when a particular amount of heat is transferred  A mole of a substance is a measure of quantity based on the number of particles making up an object 1 mole = x molecules or atoms  Q = knΔT Q = Heat (J) k = Molar specific heat (J/mol x K) n = Number of moles ΔT = Temperature change in C° or K

 Transformation between solid and liquid, liquid and gas, or solid and gas  All require the addition of energy  When water freezes into ice or steam condenses into water  Energy is released  * Although energy is being added or released during a phase change  Temperature of the substance remains constant

THE PHASES OF MATTER

During a phase change, the temperature of the mixture does not change (provided the system is in thermal equilibrium).

 Energy required per kilogram to cause a phase change in a given material  Latent heat of fusion Transforming from solid to liquid, or liquid to solid  Latent heat of vaporization Transforming from liquid to gas, or vice-versa  Latent heat values  Same in either “direction” of phase change

 Latent Heat Equations  Q = L f m  Q = L v m Q = Heat (J) m = Mass (kg) L f = Latent heat of fusion (J/kg) L v = Latent heat of vaporization (J/kg)

Ice-cold Lemonade Ice at 0 o C is placed in a Styrofoam cup containing 0.32 kg of lemonade at 27 o C. The specific heat capacity of lemonade is virtually the same as that of water. After the ice and lemonade reach an equilibrium temperature, some ice still remains. Assume that mass of the cup is so small that it absorbs a negligible amount of heat.

 Flow of thermal energy directly through a material without motion of the material itself  Example: Cast iron pan on stove  Handle eventually gets hot  Thermal Conductors: Materials that conduct heat well  Thermal Insulators: Materials that conduct heat poorly

 Process in which heat is carried from one place to another by the bulk movement of a fluid  Heat transfer through a gas or liquid caused by movement of the fluid

Hot Water Baseboard Heating and Refrigerators Hot water baseboard heating units are mounted on the wall next to the floor. The cooling coil in a refrigerator is mounted near the top of the refrigerator. Each location is designed to maximize the production of convection currents.

 Radiation  Heat transfer by electromagnetic waves  Material that is a good absorber is also a good emitter

 Global Warming & the Greenhouse Effect