AP Physics Ch 10&11 Day 1

8/3/2019 AP Physics Ch 10&11 Day 1

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Chapter 10&11 Day 1

AP Physics Objectives Relate temperature to the kinetic energy of

atoms and molecules.

Describe the changes in the temperatures of two

objects reaching thermal equilibrium.

Identify the various temperature scales, and be

able to convert from one scale to another.


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Turn off cell phones!

Pick up worksheets 10-1 MathSkills and Problem 10A

Check updated grades

Pick up Chapter 7 Review packet

Read pages 357-364


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Thermal Physics

Thermal physics is the study of

Temperature

Heat

How these affect matter


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Thermal Physics, cont

Concerned with the concepts of energy transfersbetween a system and its environment and theresulting temperature variations

Historically, the development of thermodynamicsparalleled the development of atomic theory

Concerns itself with the physical and chemicaltransformations of matter in all of its forms: solid,liquid, and gas


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Heat

The process by which energy is exchanged between

objects because of temperature differences is called heat

Objects are in thermal contactif energy can be exchanged

between them

Thermal equilibrium exists when two objects in thermal

contact with each other cease to exchange energy


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Zeroth Law of Thermodynamics

If objects A and B are separately in thermal equilibrium with a third

object, C, then A and B are in thermal equilibrium with each other.

Allows a definition of temperature


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Temperature from the Zeroth

Law Two objects in thermal equilibrium with

each other are at the same temperature

Temperature is the property that determines

whether or not an object is in thermal

equilibrium with other objects


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Thermometers

Used to measure the temperature of an object or a system

Make use of physical properties that change withtemperature

Many physical properties can be used volume of a liquid

length of a solid

pressure of a gas held at constant volume

volume of a gas held at constant pressure

electric resistance of a conductor

color of a very hot object


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Thermometers, cont

A mercury thermometer isan example of a commonthermometer

The level of the mercuryrises due to thermalexpansion

Temperature can be definedby the height of the mercurycolumn


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Temperature Scales

Thermometers can be calibrated by placing

them in thermal contact with an

environment that remains at constant

temperature

Environment could be mixture of ice and water

in thermal equilibrium

Also commonly used is water and steam in

thermal equilibrium


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Celsius Scale

Temperature of an ice-water mixture is defined as 0 C

This is thefreezing pointof water

Temperature of a water-steam mixture is defined as 100 C

This is the boiling pointof water

Distance between these points is divided into 100 segments

or degrees


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Gas Thermometer

Temperature readingsare nearly independentof the gas

Pressure varies withtemperature whenmaintaining a constantvolume


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Kelvin Scale

When the pressure of a gas goes to zero, its temperature is

273.15 C

This temperature is called absolute zero

This is the zero point of the Kelvin scale

273.15 C = 0 K

To convert: TC = TK 273.15

The size of the degree in the Kelvin scale is the same as the size of

a Celsius degree


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Pressure-Temperature Graph

All gases extrapolate to

the same temperature at

zero pressure

This temperature is

absolute zero


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Modern Definition of Kelvin

Scale Defined in terms of two points

Agreed upon by International Committee on Weights and

Measures in 1954

First point is absolute zero

Second point is the triple pointof water

Triple point is the single point where water can exist as solid,

liquid, and gas

Single temperature and pressure

Occurs at 0.01 C and P = 4.58 mm Hg


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Modern Definition of Kelvin

Scale, cont The temperature of the triple point on the

Kelvin scale is 273.16 K

Therefore, the current definition of of the

Kelvin is defined as

1/273.16 of the temperature of the triple

point of water


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Some Kelvin

Temperatures Some representative

Kelvin temperatures

Note, this scale is

logarithmic

Absolute zero has

never been reached


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Fahrenheit Scales

Most common scale used in the US

Temperature of the freezing point is 32

Temperature of the boiling point is 212

180 divisions between the points


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Comparing Temperature Scales


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Converting Among Temperature

Scales


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Practice 10A, page 363

2) The temperatures of one

northeastern state range from 105F in

the summer to -25F in winter.

Express this temperature range in

degrees Celsius and in kelvins.

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AP Physics Ch 10&11 Day 1