Heat Transfer
Essential Questions: What methods can be used to demonstrate thermal energy transfers? What are conduction, convection, and radiation, including examples?
Conduction, Convection and Radiation Thermal Energy Energy that is generated by a source Total kinetic energy of particles Measured by temperature (the average kinetic energy of particles) Can be transferred heat Kinetic energy of an object is the energy that it possesses due to its motion. Chemical energy is energy stored in the bonds of chemical compounds (atoms and molecules). It is released in a chemical reaction, often producing heat as a by-product (exothermic reaction). Batteries, biomass, petroleum, natural gas, and coal are examples of stored chemical energy. © KeslerScience.com
Conduction, Convection and Radiation 3 Ways Thermal Energy can be Transferred by heat Conduction Convection Radiation Have a pan of water boiling in the room. Discuss the three types of energy transfer using this as an example. © KeslerScience.com
Conduction, Convection and Radiation The movement of heat, once heated through radiation Solids are good conductors, particularly metals © KeslerScience.com
Conduction, Convection and Radiation Examples of Conduction – (direct contact) Touching a metal spoon in a cup of hot liquid Putting a heating pad on your back Feeling the heat from a hot poker that was in a fire place Placing a hand on top of a basket of hot rolls © KeslerScience.com
Conduction, Convection and Radiation The transfer of thermal energy though a fluid (gas or liquid) that has already been heated through radiation Due to differences in density Hot fluid (less dense) rises while cold fluid (more dense) sinks. Red (hot) rises Stop and discuss the difference in densities between hot and cold fluids. Blue (cold) sinks © KeslerScience.com
Conduction, Convection and Radiation Examples of Convection –(hot rising/cold sinking) Macaroni rising and falling in a pot of boiling water Lava lamp rising and sinking Hot magma rising in the mantle, cold sinking Hot air rising in the atmosphere, cold sinking (convection cell causing wind) Hot water rising in the oceans, cold sinking Red (hot) rises Blue (cold) sinks © KeslerScience.com
Conduction, Convection and Radiation Travels through space and other types of matter The initial transfer of thermal energy. Energy transmitted in waves or a stream of particles called Photons © KeslerScience.com
Conduction, Convection and Radiation Examples of Radiation - (waves or particles of energy called photons) Laying out in the sun at a beach Holding your hand over a burning match without touching it Feeling the warmth of a bonfire Holding your hands over a light bulb © KeslerScience.com
1. Describe the heat transfer in this picture: 2 1. Describe the heat transfer in this picture: 2. Describe the heat transfer in the wind, the Earth’s oceans, and in the Earth’s mantle. 3. Describe how sunburns are related to heat transfer. Have students complete this template either with a partner or individually. Let’s see if they can apply their learning.
Demonstrate a way to explain thermal energy transfers? Can you… Demonstrate a way to explain thermal energy transfers? Define conductions, convection and radiation and give examples? © KeslerScience.com
Determining Thermal Energy (heat) Q = mc∆T, where Q = heat energy, m = mass, and ∆T = change in temp. c= specific heat constant ∆T = (Tfinal – Tinitial) The SI unit for thermal energy is the Joule (J) © KeslerScience.com
How many joules of heat are needed to raise the temperature of 47 How many joules of heat are needed to raise the temperature of 47.5 g of aluminum from 21C to 94C, if the specific heat of aluminum is 0.90 J/g C? © KeslerScience.com
What is the specific heat of silver metal if 55 What is the specific heat of silver metal if 55.00 g of the metal absorbs 194.7 J of heat and the temperature rises 15.0C? © KeslerScience.com