Moving Thermal Energy
Differentiate between conduction, convection, and radiation. GOALS Explain common examples, such as ice in a soda, to show the direction of energy flow. Explain molecular motion a s it relates to thermal energy changes in terms of conduction, convection, and radiation. Intro Clip Differentiate between conduction, convection, and radiation. Determine the heat capacity of a substance using mass, specific heat, and temperature. Use a calorimeter
Temperature conversions Three formulas: F=(9/5C) +32 C=5/9(F-32) K=C + 273 http://wps.prenhall.com/wps/media/objects/4677/4789326/ch01_08.htm
What is energy? Energy is the ability to do work or in chemistry the ability to move or change matter. Properties of Energy Energy is always conserved. Energy can be transferred from one object to another or system by the interaction of forces Example: digestion Comes in multiple form. (KE or PE) Potential energy = stored energy Kinetic energy = energy of motion
Temperature and Heat Temperature is the measurement of the avg. KE of the molecules in a material. Heat is the transfer of KE from one material to another. Film clip
Heat flows from WARMER to COLDER!
Conduction The transfer of thermal energy in solids. Clip The transfer of thermal energy in solids. Materials must be in direct contact with each other! Ex: Heating of the bottom of a pot on stove.
Convection Transfer of thermal energy in liquids and gases. clip Transfer of thermal energy in liquids and gases. The matter actually moves from one place to another.
Radiation Clip Transfer of thermal energy by electromagnetic waves (we’ll discuses these more later) Transferring energy through space...NO MATTER IS REQUIRED!
REVIEW Clip
Specific Heat Adding Energy to a material Causes the Temperature to go up. Taking energy away from a substance causes the temp. to Go down!
Have you ever noticed that on a hot summer day the pool is cooler than the hot cement? OR maybe that the ocean is cooler than the hot sand? Why? The sun has been beating down on both of them for the same amount of time........... It takes more thermal energy to raise the temperature of water that it does the cement!
Water absorbs a lot of heat energy before its temperature changes while sand needs little heat energy before its temperature increases.
Specific Heat The amount of energy required to raise the temperature of a material (substance). It takes different amts of energy to make the same temp change in different substances. We call the amt required: Specific Heat!
Specific Heat of water The Cp is high because H2O mols. form strong bonds w/each other. It takes a lot of energy to break the bonds so that the the molecules can then start to move around faster (HEAT UP).
Example: Specific Heat of Water Cp = 4,184 Joules of energy to raise the temperature of 1kg 1°C. video clip Why Cp? Cp Stands for “Heat Capacity”
Calculating Specific Heat The Greek letter Δ means “change in”
EXAMPLE : p162 Mass = 45kg Q = 203,000J Δt = 40°-28° Δt = 12° Cp = ? Q =m x Cp x Δt Q/(m x Δt) = Cp Cp = 376 J/(kg °C)
Specific Heat Lab
Calorimeter
EOCT QUESTION
A by traveling through space as waves B by the movement of fluids C by the expansion of gases D by contact between particles
A copper ornament has a mass of 0 A copper ornament has a mass of 0.0693 kg and changes from a temperature of 20.0°C to 27.4ºC. How much heat energy did it gain? A 200 J C 540 J B 460 J D 740 J
Energy The capacity to do work or produce heat Kinetic Energy (KE) Energy of motion Anything in motion has KE Potential Energy (PE) Stored energy due to position or chemical nature
Measuring Energy Joule (J) is the metric unit for energy calorie (cal) is the energy required to raise 1g H2O 1°C. Calorie (Cal) is associated with food. 1Cal = 1000 cal. 1 cal = 4.184 J
Measuring Energy Joule (J) is the metric unit for energy calorie (cal) is the energy required to raise 1g H2O 1°C. Calorie (Cal) is associated with food. 1Cal = 1000 cal. 1 cal = 4.184 J