Thermal Energy Ch 6 Ms. Patterson Physical Science 2012

Schedule for the rest of the year

Objectives 6-1 Explain the difference between heat and temperature 6-2 Determine the thermal energy for any amount of substance 6-3 Determine if an item is an insulator or a conductor 6-4 Determine the type of heat transfer – conduction, convection or radiation 6-5 Explain the difference between types of heat transfer – conduction, convection or radiation

Section 1 - Heat Objectives: 6-1 Explain the difference between heat and temperature

Heat DEF: Energy that flows from high temperature to low temperature Which way is the heat flowing?

Temperature DEF: a measure of the average kinetic energy of the molecules of a substance

Temperature Scales Classroom is celsius (°C) Scientific is kelvin (K) Everyday is fahrenheit (°F)

Conversions Put these on your formula sheet °C = K °F = °C+32 °C = (°F-32)

Now let’s practice 58 °C = ________________ K 156 °F= ________________ °C 91 °C = ________________ °F

Specific Heat DEF: The amount of heat energy (J) needed to raise the temperature of 1kg of some material by 1  C Aka: the ability of a material to absorb or release heat.

Requires Tools Needed Mass of substance Mass of substanceBalance Change in temperature Change in temperatureThermometer Specific heat of substance Specific heat of substance Resource Chart

Substance Specific Heat in J/g°C AluminumCopperBrassSilverGoldLeadMercuryWaterIron Ice (-10 C) Glass

Comparison - Which has more heat? 5 kg of water at 100  C 1 kg of water at 100  C 1 kg of water at 70  C 1 kg of water at 70  C 1 kg of iron at 70  C 1 kg of iron at 70  C Example 1 Example 2

Q = m * c * (T f -T i )

MeasurementVariables Units change in thermal energyQ J mass mg or kg specific heat C J/g°C or J/kg°C change in temperature (T f -T i ) ∆T°C

A 30 g silver spoon cools from 60°C to 20°C. How much thermal energy did it lose? C =.235 j/g*°C Q = m * c * (Tf –Ti) Q = 30 g *.235 J/gC * 40 C Q = 282 J

 How much mass is present if -368J of thermal energy are given off when water in a pond cools from 12°C to 10°C? C = j/g°C

What is the specific heat of glass if a window pane with a mass of 230 g warms from 12°C to 20°C and the change in thermal energy is 1,546 J?

Section 2 – Transferring Thermal Energy Objectives 6-3 Determine if an item is an insulator or a conductor 6-4 Determine the type of heat transfer – conduction, convection or radiation 6-5 Explain the difference between types of heat transfer – conduction, convection or radiation

Conduction DEF: Heat transfer when the molecules in 2 objects touch – Happens in Solids, liquids, gases

Conductors DEF: material that passes heat well Examples: silver, copper, and aluminum Insulators DEF: material that does not pass heat well Examples: Wood, plastic, air, paper, cloth

Radiation DEF: Heat transfer through electromagnetic waves No matter needed for transfer! Examples Infrared light Heat from a fire or hot stove Energy from the sun!

(

Convection DEF: heat transfer through movement of fluids When a fluid is heated, it expands, becomes less dense, and rises. Cooler fluid then settles to the bottom.

Examples – Convection currents - soaring birds (aka. kettles), convection ovens, lava lamps

Convection Currents

Heat Transfer