General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 1

Energy and Matter

Temperature

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Temperature

Temperature is a measure of how hot or cold an

object is compared to another object

indicates that heat flows from the object with a higher temperature to the object with a lower temperature

is measured using a thermometer

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Temperature Scales

Temperature scales are Fahrenheit,

Celsius, and Kelvin have reference

points for the boiling and freezing points of water

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A. What is the temperature of freezing water?

1) 0 °F 2) 0 °C 3) 0 K

B. What is the temperature of boiling water?

1) 100 °F 2) 32 °F 3) 373 K

C. How many Celsius units are between the boiling and freezing points of water?

1) 100 2) 180 3) 273

Learning Check

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 5

A. What is the temperature of freezing water?

2) 0 °C

B. What is the temperature of boiling water?

3) 373 K

C. How many Celsius units are between the boiling and freezing points of water?

1) 100

Solution

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On the Fahrenheit scale, there are 180 °F between the freezing and boiling points, and on the Celsius scale, there are 100 °C.

180 °F = 9 °F = 1.8 °F 100 °C 5 °C 1 °C

In the formula for the Fahrenheit temperature, adding 32 adjusts the zero point of water from 0 °C to 32 °F.

TF = 9 (TC) + 32 ° 5

or TF = 1.8(TC) + 32 °

Fahrenheit Formula

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TC is obtained by rearranging the equation for TF.

TF = 1.8(TC) + 32 °

Subtract 32 from both sides.

TF – 32 ° = 1.8(TC) + (32 ° – 32 °)

TF – 32 ° = 1.8(TC)

Divide by 1.8. TF – 32 ° = 1.8 TC

1.8 1.8

TF – 32 ° = TC 1.8

Celsius Formula

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Solving a Temperature Problem

A person with hypothermia has abody temperature of 34.8 °C. WhatIs that temperature in °F?

TF = 1.8(TC) + 32 °

TF = (1.8)(34.8 °C) + 32 ° exact tenth’s exact

= 62.6 ° + 32 ° = 94.6 °F tenth’s

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The normal temperature of a chickadee is 105.8 °F. What is that temperature on the Celsius scale?

1) 73.8 °C

2) 58.8 °C

3) 41.0 °C

Learning Check

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 10

The normal temperature of a chickadee is 105.8 °F.

What is that temperature on the Celsius scale?

3) 41.0 °C

TC = TF – 32 °

1.8

= (105.8 – 32 °)

1.8

= 73.8 °F = 41.0 °C

1.8 ° tenth’s place

Solution

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 11

A pepperoni pizza is baked at 455 °F. What temperature is needed on the Celsius scale?

1) 423 °C

2) 235 °C

3) 221 °C

Learning Check

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A pepperoni pizza is baked at 455 °F. What temperature is needed on the Celsius scale?

2) 235 °C

TF – 32 ° = TC

1.8

(455 – 32 °) = 235 °C

1.8 one’s place

Solution

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On a cold winter day, the temperature is –15 °C.What is that temperature in °F?

1) 19 °F

2) 59 °F

3) 5 °F

Learning Check

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3) 5 °F

TF = 1.8TC + 32 °

TF = 1.8(–15 °C) + 32 °

= – 27 + 32 °

= 5 °F one’s place

Note: Be sure to use the change sign key on your calculator to enter the minus (–) sign.

1.8 x 15 +/ – = –27

Solution

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The Kelvin temperature is obtained by adding 273 to the Celsius temperature

TK = TC + 273

In the Kelvin temperature scale: There are 100 units between the freezing and boiling

points of water.

100 K = 100 °C or 1 K = 1 °C 0 K (absolute zero) is the lowest possible

temperature.

0 K = –273 °C

Kelvin Temperature Scale

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Temperatures

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What is normal body temperature of 37 °C in kelvins?

1) 236 K

2) 310 K

3) 342 K

Learning Check

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What is normal body temperature of 37 °C in kelvins?

2) 310 K

TK = TC + 273

= 37 °C + 273

= 310. K

one’s place

Solution