Temperature and Thermal Energy Chapter 9 Section 1 Temperature and Thermal Energy

Kinetic Theory of Matter Describes the motion of the particles Matter is composed of particles that are atoms, molecules or ions These particles are always in random motion Moving at different speeds in all directions Because particles are in motion, they have kinetic energy.

Temperature Measures the average kinetic energy of its particles As the movement increases, the temperature increases

Temperature Scales Fahrenheit Celsius Kelvin (starts at absolute zero) F = 9/5 C + 32, to go from Celsius to Fahrenheit Celsius C = Kelvin – 273, to go from Kelvin to Celsius C = 5/9 (F – 32), to go from Fahrenheit to Celsius Kelvin (starts at absolute zero) SI unit for temperature K = Celsius + 273, to go from Celsius to Kelvin

Temperature Conversion Examples Convert 10K to C 10K - 273 = -263C Convert 100C to K 100C + 273 = 373K Convert 86F to C 5/9 x (86 – 32) = 5/9 x 54 = 270/9 = 30C Convert 10C to F 9/5 x 10 + 32 = 90 / 5 + 32 = 18 + 32 = 50F

9.1 Temperature Conversions: Hr_ Name__________________ Date__ Copy problems, show all work, & circle answer. 77F to C - 40F to C 37C to F 20C to F - 20C to F

Thermal Energy Sum of particle potential and kinetic energy Particles have potential energy because their molecules exert attractive forces on each other As particles get further apart, the potential energy increases Thermal energy of an object changes when its temperature changes

Heat Heat is the measurement of thermal energy that flows from something at a higher temperature to something at a lower temperature

Specific Heat Specific Heat is the amount of thermal energy needed to raise the temperature of 1 kg of a specific material by 1 degree C Different materials = different specific heats On a hot day, compare sand & water temps Specific Heat of common materials (J/kgC): Water=4184 Ice=2110 Wood=1720 Air=1010 Asphalt=920 Glass=800 Sand=664 Iron=450

Measuring Specific Heat Specific heat of a material can be measured using a calorimeter An instrument for measuring the amount of heat released or absorbed in physical and chemical processes.

Change In Thermal Energy Q: Ex 1 Formula: Q = m x ΔT x C Q = m x (Tf – Ti) x C Q = change in thermal energy (J) m = mass (kg) T = Tf – Ti = change in temperature (C) C = specific heat = J/(kg x C) Ex: Find Q if m=20kg, T rises from 15-25C, Cwood=1700J/kgC Q=20x(25-15)x1700 Q=20 x 10 x 1700 Q=340,000 kgCJ/kgC Q=340,000 J

Thermal Energy Calculation Ex 2 Air has specific heat of 1010 J/kgC. Room temp warms from 20C to 25C. The change in thermal energy Q is 363,600 J. Find m. Q = m(Tf-Ti)C, divide both sides by (Tf-Ti)C, m = Q / [(Tf-Ti)C] = 363,600 / [(25-20)x1010] m = 363,600 / (5 x 1010)=363,600 / 5050 m=72kg

9.1 Thermal Energy Calculation: Hr_ Name___________________ Date__ Specific heat of water is 4184 J/kgC. How much energy is needed to heat 1 kilogram of water 5 C? Find Q. What energy Q is needed to heat 1 kg sand from 30 to 50 C if specific heat=664 J/kgC? An iron block has specific heat of 450 J/kgC and increases its temp 3 C when 2700 J of energy are added. What is the iron mass m?

9.1 Specific Heat Analysis, Date__ Name____________________ Hr__ Copy, show all work, and circle each answer. Convert 112 F to C. Convert 35 C to F. Find water thermal energy Q at 1000 kg & specific heat 4184 J/kgC if it cools by 10 C. Find thermal energy change Q of air at 72kg & specific heat 1010 J/kgC if it heats by 5 C.

Chapter 9 Section 2 States of Matter

Five States of Matter Solid Liquid Gas Plasma Bose-Einstein Condensate

Solid Solids have fixed volume and definite shape Particles are closely packed in a fixed pattern Particles constantly vibrating in place Attraction between particles are strong

Liquid State Liquids have no definite shape but have a fixed volume. Attractive force between particles are weaker than in a solid, but are strong enough to cause particles to cling together. Liquid particles are free to flow and take the shape of a container. Liquids have no definite shape but have a fixed volume.

Gas State Gases have no definite shape or volume Particles are much farther apart than in a solid or liquid Attractive forces are weak because the particles are far apart Gas containers contain mostly empty space Gas particles will spread indefinitely until evenly distributed This is called Diffusion

Plasma State Most common state of matter in the universe. Matter consisting of positively and negatively charged particles Does not have a definite shape or volume Results from collisions between particles moving at such high speeds that electrons are stripped from their atoms causing charged particles at extreme temperatures. Examples are lightning bolts, neon and fluorescent tubes, and auroras So plasmas do not behave like other matter.

Aurora Borealis

Northern Lights

Aurora

Bose-Einstein Condensate Observed in a lab in 1995 at low temps. Near absolute zero and opposite of normal solids, gas atoms are clumped so that super-atoms behave like one tiny blob of material.

Change Energy = Change Phases Melting: change from solid to liquid Heat of Fusion = energy to change from solid to liquid Freezing: liquid to solid Vaporization: liquid to gas (two types) Evaporation and Boiling Condensation: gas to liquid Sublimation: solid to gas Deposition: gas to solid

Phase Change To produce a phase change the substance must either be heated or cooled. When a phase change occurs, the average kinetic energy of the substance that is changing remains constant.

Changing States Sublimation Deposition Evaporation (multi-temp) Surface Liquid to Gas Boiling (specific temp) Internal Liquid to Gas Condensation Gas changes to liquid Sublimation Solid to Gas Deposition Gas to Solid

States of Matter Simulation http://phet.colorado.edu/en/simulation/states-of-matter

Heating Curve of a Substance

9.2 Matter States Analysis, Date__ Name____________________ Hr__ Copy and answer each in complete sentences. Explain how forces between water molecules change when an ice cube melts. Air pressure on a mountain is lower than air pressure at sea level. Explain how water boiling point is different at sea level. Explain how a hot air balloon rises in cool air.

Transferring Thermal Energy Chapter 9 Section 3 Transferring Thermal Energy

3 Ways to Transfer Thermal Energy Thermal Energy moves from one object to another in 3 ways: Conduction Convection Radiation Heat moves from warm objects to cooler objects Copy this picture & terms

Conduction Thermal energy that is transferred through the collision of particles is conduction. Faster moving atoms collide with slower moving particles As these collisions continue, energy is transferred Particles transfer heat through collisions. Some materials conduct heat better than others The best thermal conductors are metals Gases are poorer conductors than solids or liquids, which makes gases better thermal insulators.

Convection Thermal energy that is transferred through a moving fluid is convection. A fluid is a material that can change its position easily, so gas like air can be a fluid! Liquid & gas transfer heat through movement Particles that move faster get farther apart. So fluids usually to expand; water is an exception Volume increases, but mass stays the same.

Convection Currents Copy this picture

Radiation Thermal energy transfers by electromagnetic waves called radiation (also called electromagnetic energy) Infrared (IR) Ultraviolet (UV) Radiation needs no matter to transfer energy Radiation can be absorbed, reflected, or transmitted.

Thermal Insulators To prevent heat flow, use a thermal insulator. A thermal insulator is a material that traps thermal energy (keeps cold or hot). Best insulator is gas; worst would be metal. Choose products that trap air or have air pockets to prevent thermal energy loss.

9.3 NRG Transfer Analysis, Date__ Name____________________ Hr__ Copy and answer each in complete sentences. Describe how a convection current occurs. Explain why convection can’t occur in solids. Why is ceiling air warmer than air at the floor

Chapter 9 Section 4 Using Thermal Energy

Heating Systems: Forced Air Fuel is burned in furnace and heats air in an open system. Fan blows heated air, quickly changing room temperature. Cold air returns to be reheated. Code adds fresh outside air to system.

Radiator Heating Radiator Systems Closed metal container contains water Water heated and sent through pipes as hot water or steam Radiator gives off heat, usually located under a window Closed system; no water or steam is lost Usually no air movement from fans. Heat spreads slowly through room by convection but is usually constantly on so room stays warm longer. But it usually cools off slower as well.

Electric Heating Electric Heating Systems Converts electrical energy to thermal energy Often electricity is run through a metal wire which heats up. Warm wire is either exposed to air or placed under the floor. Usually no air movement from fans. Heat spreads slowly through room but is usually constantly on so room stays warm longer. But it usually cools off slower as well.

Active Solar Heating System Solar collectors contain fluid that heats up outdoors from the Sun’s radiant energy. This fluid is then pumped through the house in pipes that release the heat into each room. The fluid is then pumped outside again to collect more heat and repeat the process.

Thermodynamics First Law of Thermodynamics Increase in thermal energy of a system equals the work done on a system plus the thermal energy transferred to the system

Thermodynamics continued Second Law of Thermodynamics It is impossible for thermal energy to flow from a cool object to a warmer object unless work is done

Refrigerators & Air Conditioners These heat movers transfer thermal energy from one place to another by using gas that expands to cool things off. The gas collects unwanted heat while it condenses, removes the heat and releases it somewhere else, expands, and returns to cool things off again.

Heat Engine Device that converts thermal energy into work or mechanical energy Car Engine: Internal Combustion Engine (Bonfire = External) Fuel burned in engine chambers Cylinder moves a piston up and down Only about 25% of fuel is converted into work

Closed vs. Open System Open System Closed System Exposed to outside forces; items may escape Work is done across a boundary Closed System Self contained and sealed so nothing escapes No work done across a boundary and no outside work done