Energy and Matter

Energy Energy is the capacity to do work or produce heat. Three forms of energy: Radiant, Kinetic, & Potential Law of Conservation of Energy: Energy is neither created or destroyed, just changed from form to form. Measuring energy: Use a device called a calorimeter to measure heat. calorie: amount of heat needed to raise 1g of water 1 °C 1 Calorie = 1,000 calories Joule = SI unit of measure for Energy 1 cal = 4.184 J

Practice with energy conversions Convert 686,000 Joule to Calories 163.9 Cal 686,000 J 1 cal 1 Cal 4.184 J 1,000 cal ~164 Cal 2. Convert 47, 500 calorie to Joule 47,500 cal 4.184 J 198, 740 J 1 cal ~199,000 J

Temperature Galileo Galilei: invented first thermometer There are three temperature scales: Fahrenheit Scale Not generally used in science. Water freezes at 32°F and boils at 212°F. Celsius Scale Used in science. Water freezes at 0°C and boils at 100°C. Kelvin Scale SI unit and used in science. Same temperature increment as Celsius scale. Absolute zero is the lowest temperature possible. Absolute zero: 0 K = -273.15oC.

Temperature Temperature measure of the average KE of the particles in a sample of matter

Temperature bp H2O body temp room temp fp H2O

Temperature Conversions

What is the Fahrenheit temperature of an object at 600. K? Convert Kelvin temperature to Celsius. Convert the Celsius temperature to Fahrenheit.

What is the Fahrenheit temperature of an object at 600.K? Convert Kelvin temperature to Celsius. Convert the Celsius temperature to Fahrenheit.

Thermal Energy Thermal Energy the total energy of the particles in a material KE - movement of particles PE - forces within or between particles due to position depends on temperature, mass, and type of substance

Thermal Energy A B Which beaker of water has more thermal energy? B - same temperature, more mass 200 mL 80ºC A 400 mL B

Heat Transfer Heat Like work, heat is... thermal energy that flows from a warmer material to a cooler material Like work, heat is... measured in joules (J) a transfer of energy

Three ways Conduction-energy transfer through contact of particles Water in contact with bottom of pot Convection-energy transfer through mass movement of particles Warm water rising to top and cool water sinking to bottom of pot Radiation-energy transfer through waves Light/heat from the sun

Heat Transfer A B Why does A feel hot and B feel cold? Heat flows from A to your hand = hot. Heat flows from your hand to B = cold. 80ºC A 10ºC B

Heat Transfer Specific Heat (Cp) amount of energy required to raise the temp. of 1 kg of material by 1 degree Kelvin units: J/(kg·K) or J/(kg·°C)

Heat Transfer 50 g Al 50 g Cu Al - It has a higher specific heat. Which sample will take longer to heat to 100°C? 50 g Al 50 g Cu Al - It has a higher specific heat. Al will also take longer to cool down.

Q = m  T  Cp Heat Transfer Q: heat (J) m: mass (kg) T: change in temperature (K or °C) Cp: specific heat (J/kg·K) – Q = heat loss + Q = heat gain T = Tf - Ti

Heat Transfer heat gained = heat lost Calorimeter Coffee cup Calorimeter Calorimeter device used to measure changes in thermal energy in an insulated system, heat gained = heat lost

Heat Transfer GIVEN: WORK: m = 32 g Q = m·T·Cp Ti = 60°C A 32-g silver spoon cools from 60°C to 20°C. How much heat is lost by the spoon? GIVEN: m = 32 g Ti = 60°C Tf = 20°C Q = ? Cp = 235 J/kg·K WORK: Q = m·T·Cp m = 32 g = 0.032 kg T = 20°C - 60°C = – 40°C Q = (0.032kg)(-40°C)(235J/kg·K) Q = – 301 J

Heat Transfer GIVEN: WORK: m = 230 g Q = m·T·Cp Ti = 12°C How much heat is required to warm 230 g of water from 12°C to 90°C? GIVEN: m = 230 g Ti = 12°C Tf = 90°C Q = ? Cp= 4184 J/kg·K WORK: Q = m·T·Cp m = 230 g = 0.23 kg T = 90°C - 12°C = 78°C Q = (0.23kg)(78°C)(4184 J/kg·K) Q = 75,061 J