http://www.colorado.edu/physics/2000/index.pl http://www.harcourtschool.com/activity/states_of_ matter/index.html
Thermal Energy Ch 6-1 Temperature and Heat
Objectives Explain the kinetic theory of matter Define temperature. Explain how thermal energy and heat are related. Calculate change in thermal energy.
Objectives Explain the kinetic theory of matter Define temperature. Explain how thermal energy and heat are related. Calculate change in thermal energy. CLE 3202.2.3 Examine the applications and effects of heat energy.
Kinetic Theory of Matter 1. All matter is made up of atoms or molecules that are in constant motion. ********************
Kinetic Theory of Matter 1. All matter is made up of atoms or molecules that are in constant motion. 2. As temperature increases, so does the rate of motion.
A. Kinetic Theory of Matter 3. The motion of the particles in matter is described by the kinetic theory of matter. 4. Matter is composed of atoms, or molecules that are in constant motion.
Average Kinetic Energy Since these particles are in motion they have KINETIC ENERGY (which we learned about earlier). Here s a model of how different atoms of different states of matter move: http://www.chem.purdue.edu/gchelp/atoms/states.html
Temperature The hotter the substance, the faster the atoms move and therefore the HIGHER the average kinetic energy of the particles. SUMMARY: higher temperature, higher average kinetic energy. http://www.colorado.edu/physics/2000/index.pl
Temperature Temperature measure of the average kinetic energy of an object s atoms or molecules.
Important Temperatures: Yes, you need to memorize these. Boiling Point Freezing Point Celsius 100 0 Fahrenheit 212 32 Kelvin 373 273
C. Thermal Energy 1. Thermal Energy the total amount of the kinetic and potential energy of all atoms in an object. 2. Depends on temperature, mass, and type of substance.
Thermal Energy Thermal Energy the total energy of the particles in a material Kinetic Energy - movement of particles Potential Energy stored energy (forces between particles)
C. Thermal Energy 3. Thermal energy increases as temperature increases. 4. At constant temperature, thermal energy increases if mass increases.
Which beaker of water has more thermal energy? B - same temperature, more mass 80ºC 80ºC A B 400 ml 200 ml
D. Heat Transfer Thermal energy that flows from something at a higher temperature to something at a lower temperature is called heat.
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 10ºC A B
When heat flows into an object and its temperature rises, the change in temperature is positive.
Cont. When heat flows out of an object and its temperature decreases, the change in temperature is negative.
E. Specific Heat Specific Heat (C p ) 1. amount of energy required to raise the temp. of 1 kg of material by 1 degree Kelvin or Celsius 2. units: J/(kg K) or J/(kg C) Specific Heat Values (J/(kg K)) Water Alcohol Aluminum Carbon (graphite) Sand Iron Copper Silver 4184 2450 920 710 664 450 380 235
Which sample will take longer to heat to 100 C? 50 g Al 50 g Cu Specific Heat Values (J/(kg K)) Water Alcohol Aluminum Carbon (graphite) Sand Iron Copper Silver 4184 2450 920 710 664 450 380 235 Al - It has a higher specific heat. Al will also take longer to cool down.
E. Specific Heat Changes in thermal energy can be calculated as change in thermal energy equals mass times change in T times specific heat.
A calorimeter is used to measure specific heat
Heat Transfer Calorimeter device used to measure changes in thermal energy in an insulated system Coffee cup Calorimeter heat gained = heat lost
Discussion Question How do temperature and heat differ?
Answer Heat is thermal E that flows from something warmer to something cooler; T is related to KE of atoms in a substance.
Review: Conversions between different units of Temperature There are three different units of temperature: Kelvin, Celsius, and Farenheit. To convert between Kelvin and Celsius: Degrees Kelvin = Degrees Celsius +273 Degrees Celsius = Degrees Kelvin - 273
Converting Temperatures Practice Problems How many degrees Kelvin is equivalent to 47C? How many degrees Celsius is equivalent to 534K? How many degrees Celsius is equivalent to 41F?
Specific Heat Q = m T C p Q: heat (J) m: mass (kg) T: change in temperature (K or C) C p : specific heat (J/kg K) T = T f - T i Q = heat loss + Q = heat gain
Specific Heat Values (J/(kg K)) Water Alcohol Aluminum Carbon (graphite) Sand Iron Copper Silver 4184 2450 920 710 664 450 380 235
A 0.032-kg silver spoon cools from 60 C to 20 C. How much heat is lost by the spoon? GIVEN: m = 0.032 kg T i = 60 C T f = 20 C Q =? C p = 235 J/kg K WORK: Q = m T C p m = 0.032 kg T = 20 C - 60 C = 40 C Q = (0.032kg)(-40 C)(235J/kg K) Q = 301 J
How much heat is required to warm.23 kg of water from 12 C to 90 C? GIVEN: m =.23 kg T i = 12 C T f = 90 C Q =? C p = 4184 J/kg K WORK: Q = m T C p m = 0.23 kg T = 90 C - 12 C = 78 C Q = (0.23kg)(78 C)(4184 J/kg K) Q = 75,061 J
Objectives Explain the kinetic theory of matter Define temperature. Explain how thermal energy and heat are related. Calculate change in thermal energy. CLE 3202.2.3 Examine the applications and effects of heat energy.