welcome wednesday! 1-27-16 get ready for warm up #1 get ready to take notes on our new unit:...
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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)TRANSCRIPT
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:
• 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 motionFaster movement of atoms = greater kinetic
energy Kinetic energy is related to 2 things: 1. the temperature of a substance2. the state of matter of a substancekinetic/molecular theory
TemperatureEssential Question:What is temperature?
Temperature –a measure of the AVERAGE molecular KE Faster molecular movement = more kinetic energy
More kinetic energy = higher temperatureThe hotter it is, the faster the molecules are movingColder = 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 hotter2. They change state
Slowest moving atoms are solidsFaster moving atoms are liquidsEven faster moving atoms are gases Fastest moving atoms are in the form of plasma
• Solid –Atoms close together
Dance Floor Analogy
• Number of molecules = people• Volume= size of dance floor• Temperature= speed of music• Pressure= closeness of people/collisions of
people• More movement = more heat
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Plasma - formed at high temperatures; ionized phase of matter as found in the sun;
most common state of matter in the Universe
Phase changes
• 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 from (s) to (g)
• change from (g) to (s)
• change from (l) to (g)
Example of sublimation: dry iceExample of deposition: frost
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?