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

• Liquid –

movement

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

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

• 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?