Welcome Wednesday! 1-27-16
• Get ready for warm up #1
• Get ready to take notes on our new unit:
Thermodynamics
Warm up #1
• A 0.75-kg coconut falls out of a tree from a
distance of 8.0 meters. Determine the
coconut’s kinetic energy the instant before it
hits the ground.
Thermodynamics
• Essential question: What is
thermodynamics?
• The study of the relationship between heat
and other forms of energy (such as
mechanical, electrical, or chemical energy)
Key terms:
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Kinetic molecular theory
Temperature
Heat
Phase changes
Kinetic-molecular theory
• Essential question: What is the kinetic
molecular theory?
Theory that states that all atoms/molecules of a
substance are constantly in motion
Faster movement of atoms = greater kinetic
energy
Kinetic energy is related to 2 things:
1. the temperature of a substance
2. the state of matter of a substance
kinetic/molecular theory
Temperature
Essential Question:
What is temperature?
Temperature –
a measure of the AVERAGE
molecular KE
Faster molecular movement = more kinetic energy
More kinetic energy = higher temperature
The hotter it is, the faster the molecules are moving
Colder = slower moving molecules
Essential question: how is the kinetic
molecular theory related to states of
matter and phase changes?
As atoms/molecules increase their velocity, two
things happen:
1. They get hotter
2. They change state
Slowest moving atoms are solids
Faster moving atoms are liquids
Even faster moving atoms are gases
Fastest moving atoms are in the form of plasma
• Solid –Atoms
close
together
• Liquid –
movement
Dance Floor Analogy
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Number of molecules = people
Volume= size of dance floor
Temperature= speed of music
Pressure= closeness of people/collisions of
people
• More movement = more heat
http://www.brianmichaelsdj.com/chicken.htm
Plasma - formed at high temperatures;
ionized phase of matter as found in the
sun; most common state of matter in the
Universe
Phase changes
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Melting
Freezing
Evaporation
Condensation
Sublimation
Deposition
vaporization
• change from (s) to (l)
• change from (l) to (s)
• change from (l) to (g)
• change from (g) to (l)
• change
(s) to (g)dry ice
Example
offrom
sublimation:
• changeoffrom
(g) to (s)frost
Example
deposition:
• change from (l) to (g)
Essential Question(s):
1.What is heat?
2. What is the difference between
temperature and heat?
• Temperature tells you the amount of
KINETIC ENERGY something has
• HEAT - Energy that flows as the result of
a difference in temperature
• Heat is the transfer of energy from one
object to another
Heat & Temperature
• Heat and temperature are NOT the same thing!
• Heat – refers to total amount of thermal energy
in a substance
• Temp. – refers only to average kinetic energy
• Q: Which has more heat: 2L of boiling water or
1L of boiling water?
Essential question: how do we
measure temperature?
• 3 main systems: Celsius,
Fahrenheit, and Kelvin
Essential question: How are the
temperature scales similar and different?
• In the Fahrenheit scale, water freezes at 32 degrees
and boils at 212 degrees
• The Celsius scale divides the difference between the
freezing and boiling points of water into 100 degrees
(instead of 180).
• With the Kelvin scale, water freezes at 273 K and
boils at 373 k
Kelvin
• The Kelvin temperature scale is useful for
many scientific calculations because it
starts at absolute zero.
• It is the universal temperature
measurement used in science.
• The Kelvin scale is used because it
measures the actual energy of atoms.
Kelvin scale
• “Absolute Zero” = 0 K
–i.e., no molecular motion, therefore
no KE on the molecular level
–0 K is the lowest you can go! You can’t
stop motion more than 0.
–What would happen if we reached
absolute zero?
TEMPERATURE VS HEAT
• If a substance has a temperature, then the
substance’s particles have kinetic energy.
Therefore, the particles are moving.
• Absolute zero – 0 K – all motion of all particles
stops completely.
Essential question: What is thermal
energy?
Heat & Temperature
• Heat (Q) and temperature are NOT the same thing!
• Heat – refers to total amount of thermal energy in a substance
• Temp. – refers only to average kinetic energy
• Q: Which has more heat: 2L of boiling water or 1L of
boiling water?