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### Heat and Waves

Chapter 10 and 12 Review

Agenda:

Waves

Hooke’s Law

Amplitude, period and frequency

Types of waves

Wave speed

Interference

Standing waves

Heat

- Temperature, measuring temperature, and thermal equilibriium
- Heat transfer is energy transfer
- Specific heat and calorimetry
- Latent heat
- Heat transfer

Temperature

- Temperature measures the average kinetic energy of the atoms or molecules of a substance.
- Temperature changes when energy is added or removed.
- All objects attempt to attain thermal equilibrium by exchanging energy.

Temperature Continued

- Matter expands as temperature increases. This is called thermal expansion.
- Temperature is measured in (see your formula sheet for coversions):
- degrees Fahrenheit
- degrees Celsius
- Kelvin

Heat

- Thermal energy is the measure of the TOTAL kinetic energy of the molecules of a substance
- Heat is the transfer of energy between substances.
- Substances at different temperatures will transfer energy until they are equal.
- Like all energy, heat can be measured in Joules.

Heat and Work

- Any energy change that cannot be accounted for by a change in potential or kinetic energy can be attributed to heat (internal energy) by way of friction.

Specific Heat

- Different materials require different amounts of energy to change their temperatures.
- The energy required to raise the temperature of 1 kilogram of a substance by 1 degree Celsius is its specific heat capacity.

Calorimetry

- Specific heat capacity of substances can be determined by calorimetry.
- The amount of energy gained by the water must equal the amount of energy lost by the substance.

Energy during Phase Change

- It takes energy to change phases. TEMPERATURE DOES NOT CHANGE DURING PHASE CHANGE.
- Latent heat is the energy required to change phase.
- Problem solving: when determining the energy required to change a substance from one temperature to another, you must consider if there is a phase change or not.

Heat Transfer

- Conduction: heat transfer by direct contact between molecules
- Conductors allow the flow of heat easily
- Insulators inhibit the flow of heat.

- Convection: heat transfer through a fluid
- Radiation: energy transfer through electromagnetic waves.

Vibration and Waves:

- Hooke’s Law: the restoring force is proportional to the displacement of the object.
- Displaced objects have potential energy.

- Objects vibrate in simple harmonic motion if they behave according to Hooke’s Law (pendulums and mass-spring systems)

Measuring Simple Harmonic Motion

- Amplitude: the maximum displacement of the object
- Period: time for one complete cycle (Seconds)
- Frequency: how many cycles completed per second (Hz)

Pendulums and Mass-Spring Systems

- Period of a pendulum depends on pendulum length.
- Period of a mass spring system depends on mass and spring stiffness.

Wave Types

- Mechanical waves disturb a physical medium. Non-mechanical waves, like light, do not need a medium to travel through.
- Pulse waves are a single peak traveling. Periodic waves are repeated regular motions.

Waves Continued

- Transverse waves are perpendicular to wave motion.
- Longitudinal waves are parallel to wave motion

Wave Speed

- The speed of a wave is constant for any given medium.
- Frequency and wavelength are inversely proportional.

Interference

- When waves collide with each other, it is called interference.
- If the waves peaks are in the same direction, they add together for constructive interference.
- If the peaks are in opposite directions, they subtract for destructive interference.

Standing Waves

- Standing waves can be generated only at certain wavelengths relative to the length of the medium (L).
- 2L
- L
- (2/3)L
- (1/2)L
- (2/5)L
- etc.

Homework

- Finish study guide and check solutions.
- Review all slides, and get a good night’s sleep.

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