Thermal Energy Test Flashcards
Temperature
the average kinetic energy of molecule
Kinetic Energy
energy of motion
Thermal Expansion
when temperature rises, molecules move rapidly and spread apart
Thermal Contraction
when temperature lowers, molecules move slowly and is closer together
Potential Energy
the attraction between molecules, more mass more potential energy
Thermal Energy
Potential + Kinetic energy
Heat
Movement of energy from high to low temepratures
Thermal Equilibrium
there is no temperature difference, (no temp. exchange)
Conduction
heat transfer through direct contact
Convection
heat transfer from one location to another through liquid or gas
Radiation
heat transfer through electromagnetic radiation (UV Lights)
Conductors
materials that allows heat to transfer easily
Insulators
(opposite of conductors) does not pass heat easily
Specific Heat
describes the amount of energy in Joules from 1kg to 1C (Inversely proportional)
Thermodynamics
relationship between work and heat
1st Law of Thermodynamics
energy cannot be created or destroyed, only transformed/transferred
2nd Law of Thermodynamics
heat flows from low to high temp
Work
force upon an object causing it to move
When a liquid is cooled, the liquid molecules-
(B) move slower than before, (C) experience thermal contraction
heat transfer that occurs in outer space
(C) radiation
an insulator is a material that has molecules that
do not transfer heat easily
The following objects are all heated from 10°C to 30°C. Which object will transfer the most energy to your hand?
a. 5kg apples
b. 2kg apples
c. 5kg gold
d. 2kg gold
5 kg apples
Two objects of the same material but different masses are subjected to the same thermal energy input.
object with less mass will have more temperature change
All of the following are examples of conductors except ___.
a. silver
b. water
c. air
d. aluminum
air
A 80°C object and a 60°C object sit (not touching) in a 21°C environment. Which best explains what will happen?
the environment will get warmer
Which is an example of heat transfer by convection?
water boiling in a pot
Which of the following is an example of energy conservation?
a. An apple hangs suspended from a tree.
b. A person stands on tiptoes.
c. A car waits at a red light.
d. A hockey puck slides to a stop due to friction.
a hockey puck slides to a stop due to friction
When energy is transferred as heat, the amount of usable energy ___.
remains the same
How are temperature and kinetic energy related?
temperature is the measurement of the average kinetic energy of molecules
Describe what happens to motion and spacing of molecules when heated or cooled for a:
a. liquid
b. solid
c. gas
the molecules always move slow and get closer (contract) when cooled. When heated, they expand and move around faster.
what does a thermometer measure
temperature
Describe characteristics of the three temperature scales including freezing and boiling point of water for each.
Boiling Point-
Kelvin- 373
Celsius- 100
Fahrenheit- 212
Freezing-
Kelvin-273
Celsius- 0
Fahrenheit- 32
using the ideas of thermal expansion and contraction, describe how a thermometer works
temperature increase cause liquid inside thermometer to expand, therefore temperature rises. Temperature decrease causes liquid inside to extract, therefore temperature falls
what state of matter has the most and least potential energy?
Solid - Most
Gas - Least
what 2 types of energy do molecules possess
potential and kinetic
explain why thermal energy and temperature, though related, are different
Temperature uses kinetic energy while thermal energy uses kinetic and potential energy
provide an example of when two substances might have the same temperature but different thermal energy.
A cup of water and a bucket of water. They could both have the same temperature, but the bucket of water is holding more, so it has more molecules.
how are heat flow and temperature differences related?
the greater the difference between temps, the more heat will flow
which will cool fastest initially in a room temperature room? boiling water or lukewarm water?
boiling water
will heat flow between two objects touching that have the same temperature?
no because no heat can be exchanged if they are the same temperature (they’ve reached thermal equilibrium)
which direction does heat flow? give an example
heat flows from high to low. In a pot of boiling water, the hot water from the bottom rises to the top as the the cooler water from the top sinks down to the bottom
three methods of thermal energy transfer
conduction, convection, radiation
do all objects emit the same amount of radiation? why or why not?
hotter objects transfer more heat through radiation since they have more heat to release
why does conduction primarily occur in solids
molecules are very close in solids, therefore heat is easier to transfer
what is the difference between conductors and insulators?
conductors allow heat to transfer easily while insulators don’t
examples of conductors
metal, aluminum, silver
example of insulators
glass, air, rubber
what kind of material would make tea boil quicker in a kettle
metal
what would you use to maximize and minimize heat transfer
Max - metal
Min - air
If you have several spoons made of conducting materials and insulating materials, which will feel cooler to the touch and why?
metal because it takes thermal energy quicker
state wheat her the variable is “inversely” or “directly” proportional to the temperature change
a. mass
b. specific heat
c. thermal energy transferred
mass - inversely; a bucket and a cup of water are over a fire, the cup of water changes faster than the bucket, since there is less mass to heat up
specific heat - inversely; the smaller the specific heat, the more temperature change it will have
thermal energy transfer - directly; the more thermal energy, the more temperature change
Suppose you took a bite of pie that was at a certain temperature. The crust doesn’t burn you but the filling does. Using the idea of specific heat, explain why the filling burned you but the crust didn’t even though they had the same temperature.
The filling needs more energy to cool down, so even though the crust is cooled down, it doesn’t need as much energy as the filling to cool down, so the filling still burns you. The filing transfers more thermal energy because it has less specific energy than the crust.
