* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 16.2 Heat and Thermodynamics
Survey
Document related concepts
Underfloor heating wikipedia , lookup
Solar water heating wikipedia , lookup
Intercooler wikipedia , lookup
Heat equation wikipedia , lookup
Passive solar building design wikipedia , lookup
Thermal comfort wikipedia , lookup
Hyperthermia wikipedia , lookup
Copper in heat exchangers wikipedia , lookup
Thermal conductivity wikipedia , lookup
Cogeneration wikipedia , lookup
Building insulation materials wikipedia , lookup
Solar air conditioning wikipedia , lookup
Transcript
16.2 Heat and Thermodynamics 16.2 Heat and Thermodynamics Key Concepts • Why is conduction slower in gases than in liquids or solids? • In what natural cycles do convection currents occur? • How does an object’s temperature affect radiation? • What are the three laws of thermodynamics? 16.2 Heat and Thermodynamics Conduction Conduction is the transfer of thermal energy with no overall transfer of matter. ____ – occurs within a material or between materials that are ___________________ touching collisions – due to the ______________ between particles Newton’s cradle shows how kinetic energy is transferred through the collisions of the balls 16.2 Heat and Thermodynamics Conduction slower Conduction in gases is ____________ than in liquids and solids because the particles in a gas are ______________ apart, making them farther collide _______ often. less 16.2 Heat and Thermodynamics Thermal Conductors A thermal conductor is a material that conducts thermal well energy ________. good Metals are __________ thermal conductors. The bottom of this metal frying pan first heats up ________ and the handle ________ last 16.2 Heat and Thermodynamics Conduction better Tile is a ____________ conductor than wood. A tile floor feels ____________ than a wooden colder floor when you walk on it because the tile ________________ thermal energy more rapidly transfers away from your skin. Heat flows from warm objects to cold objects Warmer foot colder tile 16.2 Heat and Thermodynamics A material that conducts thermal energy poorly is called a thermal ____________________. insulator Air ________ is a very good insulator. trapped air to slow down Examples: Foam cups use ___________ conduction...so do wool sweaters 16.2 Heat and Thermodynamics Convection Convection is the transfer of thermal energy when particles of a fluid __________ move from one place to another. Quick Review…what states of matter are considered fluids? Liquids and gases Convection currents are important in many natural cycles, such as… • ocean _____________ currents weather • _____________ systems hot _______ rock in Earth’s interior • movements of ______ 16.2 Heat and Thermodynamics Convection Passing sandbags along a line is like A. ______________ transferring thermal energy by convection. air B. The arrows show convection of _______ in an oven. 16.2 Heat and Thermodynamics Convection current A convection _____________ occurs when a fluid circulates in a __________ as it alternately heats loop up and cools down. • Air at the bottom of an oven heats up, expands, and becomes less dense. The hot air rises ____________. • Rising hot air cools as it moves away _________ from the heat source. • The cool air contracts, become sinks more dense, and _________ 16.2 Heat and Thermodynamics Radiation waves Radiation is the transfer of energy by __________ space moving through ______________. All objects radiate energy. As an object’s temperature _____________, the increases ________ at which it radiates energy also rate increases. 16.2 Heat and Thermodynamics Radiation sun The ______ warms you by radiation on a clear day. Heat lamps used in restaurants are another example of radiation. 16.2 Heat and Thermodynamics Thermodynamics transfers The study of _________________ between thermal energy and other forms of energy is called thermodynamics. Joule James Prescott ____________ (1818-1889) carefully measured the energy changes in a system falling weight – his system included a ________ pushed a paddle wheel in a that ________ container of water. – Joule found that the ________ work done by the falling weight almost exactly thermal energy equaled the ___________ gained by the water. 16.2 Heat and Thermodynamics Thermodynamics First Law of Thermodynamics The first law of thermodynamics states that conserved energy is ______________. Energy cannot be created or destroyed, but it forms can be converted into different ____________. 16.2 Heat and Thermodynamics Thermodynamics Pushing on the pump does work ________ on the system. Some of the work is converted into ___________ thermal energy, which heats the air in the pump and the tire. 16.2 Heat and Thermodynamics Thermodynamics Second Law of Thermodynamics The second law of thermodynamics states that cold thermal energy can flow from ___________ objects to ___________ objects only if _______ warm work is done on the system. 16.2 Heat and Thermodynamics Thermodynamics • Example A refrigerator must do work to cold food transfer thermal energy from the _______ warm room air. compartment to the ________ • The thermal energy is released by _________ coils at the bottom or in the back of the refrigerator. 16.2 Heat and Thermodynamics Thermodynamics heat A heat engine is any device that converts _____ into __________ work • Thermal energy that is not converted into work is waste heat. called _________ • Waste heat is transferred the ________________ surrounding environment. 16.2 Heat and Thermodynamics Thermodynamics Spontaneous changes will always make a system _______ orderly, unless work is done on the less system. For example, if you walk long enough, your shoelaces will become __________. untied Disorder in the universe as a whole is always ____________________. increasing 16.2 Heat and Thermodynamics Thermodynamics The third law of thermodynamics states that absolute zero cannot be reached. _________ This physicist uses a laser to cool rubidium atoms to 3 billionths of a Kelvin above absolute zero. 16.2 Heat and Thermodynamics Assessment Questions 1. What form of energy transfer requires the motion of particles of a fluid? a. b. c. d. conduction convection radiation insulation 16.2 Heat and Thermodynamics Assessment Questions 2. Thermal energy can move from a cooler object to a warmer object when a. b. c. d. the warmer object is larger. the cooler object has more thermal energy. energy is transferred by radiation. work is done on the system. 16.2 Heat and Thermodynamics Assessment Questions 3. According to the third law of thermodynamics, it is impossible a. to cool an object to absolute zero. b. transfer thermal energy from a cooler object to a warmer object. c. convert energy from one form to another. d. account for all of the energy in a system. 16.2 Heat and Thermodynamics Assessment Questions 4. All metals are good thermal insulators. True False