4. temperature and heat

7/25/2019 4. Temperature and Heat

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UNIT 3: TEMPERATURE AND

HEAT


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OBJECTIVES

Distinguish between heat and temperature.

Explain how temperature is measured.

Compare the three common temperature

scales.

Solve problems in changing one scale to

another.


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Temperature and Heat

Kinetic theory of matter - all matter ismade up of tiny particles called atoms

or molecules.

These particles are always moving, and

it is this movement that helps decidewhat state of matter exists (solid,

liquid, gas).

The particles have potential and kinetic

energy (kineticas they are moving, and

potential as they are potentially

attracted or repulsed by each other).

The TOTAL of all these forms of

energy in a particular substance is

called its thermal energy.
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When you put a flame to a liquid, the liquid

becomes warmer or hotter.Why?


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The molecules are made to race back and forth faster. In

other words, they gain kinetic energy. In general, the

warmer or hotter an object, the more kinetic energy its

atoms and molecules possess.


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is the hotness or coldness of a

body. is the energy that transfers from a body

of higher temperature to another body of lower

temperature. A quantity of thermal energy

absorbed or given off by a body.

Temperature

Heat


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Temperature indicates the direction in which heat

flowing while heat is actual energy transferred.

In a set-up, a glass and pitcher filled with warm water of the sametemperature. Which water will dissolve an ice cube faster?


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Temperature indicates the direction in which heat

flowing while heat is actual energy transferred.

A drop of boiling water on your hand will not burn you. But if a

glass of boiling water is accidentally spilled on your hand. What

do you think will happen?


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How do we measure Temperature?

Thermometer

any thermal sensor that measures temperature.

Used to measure the hotness or coldness of

something.

Calibrations- lines on a thermometer.

A thermometer can be calibrated by Fahrenheit,

Celsius, or Kelvin


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Kinds of Thermometer

Liquid-in-glass thermometer

Made of a glass tube with abulb on one end

Increase temperature- liquid

expand and rises up the

narrow tube

Decrease temperature-the

liquid contracts and falls.


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Rotary thermometer

Consists of a coiled bimetallic strip

(iron and brass) joined together.

Brass- expands more than iron does

when heated.

When bimetallic strip is heated, one

side of it becomes longer than theother.

Increase temperature- strip coils up

more and the pointer moves around

a scale.


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Thermocouple thermometer

An electronic thermometer

Wires made up of two different

metals are twisted together.

When the wire tips are heated, a

small electric current is

generated

The amount of current depends

on the temperature

Commonly used in measuring

the temperature of ovens and

furnaces.


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Liquid crystal thermometer

Consists of liquid crystalsUsed particularly with

young children as a

forehead fever

thermometerUsed for measuring the

temperature of fish tanks.


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Temperature Scales

Fahrenheit scale

Gabriel Fahrenheit

32 freezing point

212

boiling point at sea level F degree Fahrenheit


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Temperature Scales

Celsius scale

Anders Celsius

0 freezing point

100

boiling point C degree celsius


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Temperature Scales

Kelvin scale

Intervals are the same with Celsius scale. Any temperature can be changed to Celsius by

adding 273 to it.

273 freezing point

373 boiling point

-273 Absolute zeroLowest possible temperature

It means that there is no more energy can be removed from

matter.


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Temperature Scales


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How to change readings from one

scale to another?

Fahrenheit to celcius

C =

5

9 (F

32)EQUATION 1


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scale to another?

From equation 1, solve for Fahrenheit

59F = C + 32 EQUATION 2


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scale to another?

Celsius to Kelvin

C = K - 273 EQUATION 3


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scale to another?

From equation 3, solve for Kelvin

K = C + 273 EQUATION 4


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TEMPERATURE SCALES

CELSIUS FAHRENHEIT KELVIN

Boiling pt of water 1000C 2120F 373 K

Freezing point of water 00C 320F 273 K

Celsius to Fahrenheit: 0F = 9/5(0C) + 32

Fahrenheit to Celsius: 0C = 5/9 (0F 32)

Celsius to Kelvin: K = 0C + 273


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SAMPLE PROBLEM:

The normal body temperature is 37C.How will you express this temperature inF and K?

The highest atmospheric temperature everrecorded on Earth was 57.8C. how willyou express this temperature in F and K?


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SAMPLE PROBLEM:

A science article refers to atemperature of 300.0 K. What is the

equivalent Celsius and Fahrenheittemperature?


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TRY IT!

A. The average human body temperature is 98.6F. What is the equivalent temperature on the

Celsius scale?

B. The melting points mercury, copper and oxygenare 234 K, 1356 K, and 54.4 K respectively.What are the Celsius and Fahrenheit equivalentsof these substances?

4. temperature and heat

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