Chapter Two

Measurements inChemistry

Fundamentals of General, Organic & Biological Chemistry

2

Stating a Measurement

In every measurement, a number is followed by a unit.

Observe the following examples of measurements:

number + unit35 m

0.25 L 225 lb 3.4 hr

3

The Metric System (SI)

The metric system is A decimal system

based on 10. Used in most of the

world. Used by scientists

and in hospitals.

4

Units in the Metric SystemIn the metric and SI systems, a basic unit identifies each type of measurement:

5

Length Measurement

In the metric system, length is measured in meters using a meter stick.

The metric unit for length is the meter (m).

6

Volume Measurement

Volume is the space occupied by a substance.

The metric unit of volume is the liter (L).

The liter is slightly bigger than a quart.

A graduated cylinder is used to measure the volume of a liquid.

7

Mass Measurement

The mass of an object is the quantity of material it contains.

A balance is used to measure mass.

The metric unit for mass is the gram (g).

8

In each of the following, indicate whether the unit describes 1) length 2) mass or 3) volume. ____ A. A bag of tomatoes is 4.6 kg.

____ B. A person is 2.0 m tall.

____ C. A medication contains 0.50 g Aspirin.

____ D. A bottle contains 1.5 L of water.

Learning Check

9

In each of the following, indicate whether the unit describes 1) length 2) mass or 3) volume.

2 mass A. A bag of tomatoes is 4.6 kg.

1 length B. A person is 2.0 m tall.

2 mass C. A medication contains 0.50 g

Aspirin.

3 volume D. A bottle contains 1.5 L of water.

Solution

10

Learning Check

Identify the measurement that has a metric unit. A. John’s height is

1) 1.5 yards 2) 6 feet 3) 2 meters

B. The volume of saline in the IV container is1) 1 liter 2) 1 quart 3) 2 pints

C. The mass of a lemon is1) 12 ounces 2) 145 grams 3) 0.6 pounds

11

Solution

A. John’s height is

3) 2 meters

B. The volume of saline in the IV container is

1) 1 liter

C. The mass of a lemon is

2) 145 grams

12

Scientific Notation

A number in scientific notation contains a coefficient and a power of 10.

coefficient power of ten coefficient power of ten

1.5 x 102 7.35 x 10-4

Place the decimal point after the first digit. Indicate the spaces moved as a power of ten.

52 000 = 5.2 x 104 0.00378 = 3.78 x 10-3

4 spaces left 3 spaces right

13

Learning Check

Select the correct scientific notation for each.

A. 0.000 008

1) 8 x 106 2) 8 x 10-6 3) 0.8 x 10-5

B. 72 000

1) 7.2 x 104 2) 72 x 103 3) 7.2 x 10-4

14

Solution

Select the correct scientific notation for each.

A. 0.000 008

2) 8 x 10-6

B. 72 000

1) 7.2 x 104

15

Learning Check

Write each as a standard number.

A. 2.0 x 10-2

1) 200 2) 0.02 3) 0.020

B. 1.8 x 105

1) 180 0002) 0.000018 3) 18 000

16

Solution

Write each as a standard number.

A. 2.0 x 10-2

3) 0.020

B. 1.8 x 105

1) 180 000

17

Measured Numbers

You use a measuring tool to determine a quantity such as your height or the mass of an object.

The numbers you obtain are called measured numbers.

18

. l2. . . . l . . . . l3 . . . . l . . . . l4. . cm

To measure the length of the blue line, we read the markings on the meter stick.

The first digit 2 plus the second digit 2.7

Estimating the third digit between 2.7–2.8gives a final length reported as

2.75 cm

or 2.76 cm

Reading a Meter Stick

Chapter 01 Slide 19

Accuracy – how close a measurement is to the true value

Precision – how close a set of measurements are to each other

accurate&

precise

precisebut

not accurate

not accurate&

not precise

20

good accuracygood precision

Mass of a Tennis Ball

21

good accuracypoor precision

Mass of a Tennis Ball

22

poor accuracypoor precision

Mass of a Tennis Ball

23

Known + Estimated Digits

In the length measurement of 2.76 cm,

the digits 2 and 7 are certain (known).

the third digit 5(or 6) is estimated (uncertain). all three digits (2.76) are significant including

the estimated digit.

24

Learning Check

. l8. . . . l . . . . l9. . . . l . . . . l10. . cm

What is the length of the red line?

1) 9.0 cm

2) 9.03 cm

3) 9.04 cm

25

Solution

. l8. . . . l . . . . l9. . . . l . . . . l10. . cm

The length of the red line could be reported as

2) 9.03 cm

or 3) 9.04 cm

The estimated digit may be slightly different.

Both readings are acceptable.

26

. l3. . . . l . . . . l4. . . . l . . . . l5. . cm

The first and second digits are 4.5. In this example, the line ends on a mark. Then the estimated digit for the hundredths

place is 0. We would report this measurement as 4.50 cm.

Zero as a Measured Number

27

Exact Numbers

An exact number is obtained when you count objects or use a defined relationship.Counting objects

2 soccer balls4 pizzas

Defined relationships1 foot = 12 inches1 meter = 100 cm

An exact number is not obtained with a measuring tool.

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Learning Check

A. Exact numbers are obtained by 1. using a measuring tool

2. counting3. definition

B. Measured numbers are obtained by 1. using a measuring tool

2. counting3. definition

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Solution

A. Exact numbers are obtained by

2. counting

3. definition

B. Measured numbers are obtained by

1. using a measuring tool

30

Learning Check

Classify each of the following as an exact (1) or a

measured (2) number.

A.__Gold melts at 1064°C.

B.__1 yard = 3 feet

C.__The diameter of a red blood cell is 6 x 10-4 cm.

D.__There are 6 hats on the shelf.

E.__A can of soda contains 355 mL of soda.

31

Classify each of the following as an exact (1) or a

measured(2) number.

A. 2 A measuring tool is required.

B. 1 This is a defined relationship.

C. 2 A measuring tool is used to determine

length.

D. 1 The number of hats is obtained by counting.

E. 2 The volume of soda is measured.

Solution

32

2.4 Measurement and Significant FiguresEvery experimental measurement, no matter how precise, has a degree of uncertainty to it because there is a limit to the number of digits that can be determined.

Chapter 01

Slide 33

Accuracy, Precision, and Significant Figures

length = 1.74 cm

0 1 2 43cm

1.7 cm < length < 1.8 cm

34

Rules for determining significant figures

1. Zeroes in the middle of a number are significant. 69.08 g has four significant figures, 6, 9, 0, and 8.

2. Zeroes at the beginning of a number are not significant. 0.0089 g has two significant figure, 8 and 9.

3. Zeroes at the end of a number and after the decimal points are significant. 2.50 g has three significant figures 2, 5, and 0.

25.00 m has four significant figures 2, 5, 0, and 0.

35

4. Zeroes at the end of a number and before an implied decimal points may or may not be significant. 1500 kg may have two, three, or four significant figures. Zeroes here may be part of the measurements or for simply to locate the unwritten decimal point.

36

Which of the following measurements has three significant figures?

a. 1,207 g

b. 4.250 g

c. 0.006 g

d. 0.0250 g

e. 0.03750 g

37

Which of the following measurements has three significant figures?

a. 1,207 g

b. 4.250 g

c. 0.006 g

d. 0.0250 g

e. 0.03750 g

38

Which of the following numbers contains four significant figures?

a. 230,110

b. 23,011.0

c. 0.23010

d. 0.0230100

e. 0.002301

39

Which of the following numbers contains four significant figures?

a. 230,110

b. 23,011.0

c. 0.23010

d. 0.0230100

e. 0.002301

40

2.6 Rounding off Numbers

Often calculator produces large number as a result of a calculation although the number of significant figures is good only to a fewer number than the calculator has produced – in this case the large number may be rounded off to a smaller number keeping only significant figures.

41

Rules for Rounding off Numbers: Rule 1 (For multiplication and divisions): The answer can’t have more significant figures than either of the original numbers.

42

Rule 2 (For addition and subtraction): The answer should have minimum decimal places.

43

How many significant figures should be shown for the calculation?

1 2 3 4 5

1.25 0.45

2.734

44

How many significant figures should be shown for the calculation?

1 2 3 4 5

1.25 0.45

2.734

45

How many significant figures are there in the following number: 1.200 X 109?

1. 4

2. 3

3. 2

4. 1

5. Cannot deduce from given information.

46

Correct Answer:

Zeros that fall both at the end of a number and after the decimal point are always significant.

1.200 109

1. 4

2. 3

3. 2

4. 1

5. Cannot deduce from given information.

47

6.220 1.0

+ 125

How many significant figures are there in the following summation:

1. 22. 33. 44. 55. 6

48

6.220 1.0

+ 125 132.220

Correct Answer:

In addition and subtraction the result can have no more decimal places than the measurement with the fewest number of decimal places.

1. 22. 33. 44. 55. 6

49

How many significant figures are there in the result of the following multiplication:

(2.54) (6.2) (12.000)

1. 22. 33. 44. 5

50

Correct Answer:

In multiplication and division the result must be reported with the same number of significant figures as the measurement with the fewest significant figures.

(2.54) (6.2) (12.000) = 188.976 = 190

1. 22. 33. 44. 5

51

2.7 Problem Solving: Converting a Quantity from One Unit to Another

Factor-Label-Method (Unit Conversion Factor): A quantity in one unit is converted to an equivalent quantity in a different unit by using a conversion factor that expresses the relationship between units.

52

53

When solving a problem, set up an equation so that all unwanted units cancel, leaving only the desired unit. For example, we want to find out how many kilometers are there in 26.22 mile distance. We will get the correct answer if we multiply 26.22 mi by the conversion factor km/mi.

54

In working a problem, start with the initial unit.

Write a unit plan that converts the initial unit to the final unit.

Unit 1 Unit 2 Select conversion factors that cancel the

initial unit and give the final unit.Initial x Conversion = Final

unit factor unitUnit 1 x Unit 2 = Unit 2

Unit 1

Problem Setup

55

Setting up a Problem

How many minutes are 2.5 hours?Solution: Initial unit = 2.5 hrFinal unit = ? minUnit Plan = hr min

Setup problem to cancel hours (hr). Inital Conversion Final

unit factor unit2.5 hr x 60 min = 150 min (2 SF)

1 hr

56

A rattlesnake is 2.44 m long. How long is the snake in cm?

1) 2440 cm

2) 244 cm

3) 24.4 cm

Learning Check

57

A rattlesnake is 2.44 m long. How long is the snake in centimeters?

2) 244 cm

2.44 m x 100 cm = 244 cm

1 m

Solution

58

Often, two or more conversion factors are required to obtain the unit of the answer.

Unit 1 Unit 2 Unit 3 Additional conversion factors are placed in

the setup to cancel the preceding unitInitial unit x factor 1 x factor 2 = Final unit

Unit 1 x Unit 2 x Unit 3 = Unit 3 Unit 1 Unit 2

Using Two or More Factors

59

How many minutes are in 1.4 days?Initial unit: 1.4 days

Unit plan: days hr min

Set up problem: 1.4 days x 24 hr x 60 min = 2.0 x 103 min

1 day 1 hr 2 SF Exact Exact = 2 SF

Example: Problem Solving

60

Be sure to check your unit cancellation in the setup.

What is wrong with the following setup?1.4 day x 1 day x 1 hr 24 hr 60 min Units = day2/min is Not the final unit needed Units don’t cancel properly.

The units in the conversion factors must cancel to give the correct unit for the answer.

Check the Unit Cancellation

61

An adult human has 4650 mL of blood. How many gallons of blood is that?

Unit plan: mL qt gallon

Equalities: 1 quart = 946 mL

1 gallon = 4 quarts

Learning Check

62

Unit plan: mL qt gallon

Setup:

4650 mL x 1 qt x 1 gal = 1.23 gal

946 mL 4 qt

3 SF exact exact 3 SF

Solution

63

Identify the initial and final units. Write out a unit plan. Select appropriate conversion factors. Convert the initial unit to the final unit. Cancel the units and check the final unit. Do the math on a calculator. Give an answer using significant figures.

Typical Steps in Problem Solving

64

If a ski pole is 3.0 feet in length, how long is the ski pole in mm?

Learning Check

65

3.0 ft x 12 in x 2.54 cm x 10 mm =

1 ft 1 in. 1 cm

Check factor setup: Units cancel properly

Check final unit: mm

Calculator answer: 914.4 mm

Final answer: 910 mm (2 SF rounded)

Solution

66

If your pace on a treadmill is 65 meters per minute, how many minutes will it take for you to walk a distance of 7500 feet?

Learning Check

67

7500 ft x 12 in. x 2.54 cm x 1 m

1 ft 1 in. 100 cm

x 1 min = 35 min 65 m final answer (2 SF)

Solution

68

Clinical Factors

Conversion factors are also possible when working with medications.

A drug dosage such as 20 mg Prednisone per tablet can be written as

20 mg Prednisone and 1 tablet

1 tablet 20 mg Prednisone

69

Learning Check

The dosage ordered is 400 mg of Erythromycin four times a day (q.i.d)*. If the oral suspension contains 200 mg Erythromycin/5 mL, how many mL will be given each time?

1) 5 mL

2) 10 mL

3) 40 mL

*:Latin quater in die

70

Solution

The dosage ordered is 400 mg of Erythromycin four times a day (q.i.d). If the oral suspension contains 200 mg Erythromycin/5 mL, how many mL will be given each time?

2) 10 mL

400 mg x 5 mL = 10 mL

200 mg

71

Temperature Scales

Temperature is measured using the Fahrenheit, Celsius, and Kelvin temperature scales.

The reference points are the boiling and freezing points of water.

72

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

73

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

74

On the Fahrenheit scale, there are 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 Fahrenheit, the value of 32 adjusts the zero point of water from 0°C to 32°F.

°F = 9/5 T°C + 32

or °F = 1.8 T°C + 32

Fahrenheit Formula

75

The equation for Fahrenheit is rearranged to calculate T°C.

°F = 1.8 T°C + 32 Subtract 32 from both sides and divide by 1.8.

°F – 32 = 1.8T°C ( +32 – 32)°F – 32 = 1.8 T°C

1.8 1.8°F – 32 = T°C

1.8

Celsius Formula

76

A person with hypothermia has a body temperature of 34.8°C. What is that temperature in °F? °F = 1.8 (34.8°C) + 32 exact tenth's exact

= 62.6 + 32= 94.6°F

tenth’s

Solving A Temperature Problem

77

The normal temperature of a chickadee is 105.8°F. What is that temperature in °C?

1) 73.8 °C

2) 58.8 °C

3) 41.0 °C

Learning Check

78

3) 41.0 °C

°C = (°F – 32)

1.8

= (105.8 – 32)

1.8

= 73.8°F

1.8° = 41.0°C

Solution

79

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

1) 437 °C

2) 235°C

3) 221°C

Learning Check

80

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

2) 235°C

(455 – 32) = 235°C 1.8

Solution

81

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

82

3) 5°F

°F = 1.8(–15°C) + 32

= – 27 + 32

= 5°F

Note: Be sure to use the change sign key on your calculator to enter the minus – sign. 1.8 x 15 +/ – = –27

Solution

83

2.10 Energy and HeatEnergy: Capacity to do work or supply energy.Classification of Energy:1. Potential Energy: stored energy. Example: a coiled spring have potential

energy waiting to be released. 2. Kinetic Energy: energy of motion.

Example, when the spring uncoil potential energy is converted to the kinetic energy.

84

Learning Check

Identify the energy as 1) potential or 2) kinetic

A. Roller blading.

B. A peanut butter and jelly sandwich.

C. Mowing the lawn.

D. Gasoline in the gas tank.

85

Solution

Identify the energy as 1) potential or 2) kinetic

A. Roller blading. (2 kinetic)

B. A peanut butter and jelly sandwich. (1 potential)

C. Mowing the lawn. (2 kinetic)

D. Gasoline in the gas tank. (1 potential)

86

Energy has many forms: Mechanical Electrical Thermal (heat) Chemical Solar (light) Nuclear

Forms of Energy

87

Heat energy flows from a warmer object to a colder object.

The colder object gains energy when it is heated.

During heat flow, the loss of heat by a warmer object is equal to the heat gained by the colder object.

Heat

88

Heat is measured in calories or joules.

1 kilocalorie (kcal) = 1000 calories (cal)

1 calorie = 4.18 Joules (J)

1 kJ = 1000 J

Some Equalities for Heat

89

Specific heat is the amount of heat (calories or Joules) that raises the temperature of 1 g of a substance by 1°C.

Specific Heat

90

A. A substance with a large specific heat 1) heats up quickly 2) heats up slowly

B. When ocean water cools, the surrounding air 1) cools 2) warms 3) stays the same

C. Sand in the desert is hot in the day and cool at night. Sand must have a

1) high specific heat 2) low specific heat

Learning Check

91

A. A substance with a large specific heat

2) heats up slowly

B. When ocean water cools, the surrounding air

2) warms

C. Sand in the desert is hot in the day and cool

at night. Sand must have a

2) low specific heat

Solution

92

When 200 g of water are heated, the water temperature rises from 10°C to 18°C.

If 400 g of water at 10°C are heated with the same amount of heat, the final temperature would be1) 10 °C 2) 14°C 3) 18°C

200 g400 g

Learning Check

93

When 200 g of water are heated, the water temperature rises from 10°C to 18°C.

If 400 g of water at 10°C are heated with the same amount of heat, the final temperature would be2) 14°C

200 g400 g

Solution

94

To calculate the amount of heat lost or gained by a substance, we need the Specific Heat of substance, T, and the mass of the substance.

Heat = g x T x cal (or J) = cal ( or J) g °C

Calculation with Specific Heat

95

A hot-water bottle contains 750 g of water at 65°C. If the water cools to body temperature (37°C), how many calories of heat could be transferred to sore muscles?

The temperature change is 65°C - 37°C = 28°C.heat (cal) = g x T x Sp. Ht. (H2O)

750 g x 28°C x 1.00 cal g°C

= 21 000 cal

Sample Calculation for Heat

96

How many kcal are needed to raise the temperature of 120 g of water from 15.0°C to 75.0°C?

1) 1.8 kcal

2) 7.2 kcal

3) 9.0 kcal

Learning Check

97

How many kcal are needed to raise the temperature of 120 g of water from 15.0°C to 75.0°C?

2) 7.2 kcal

Learning Check

98

In chemical reactions, the potential energy is often converted into heat. Reaction products have less potential energy than the reactants – the products are more stable than the reactants.

Stable products have very little potential energy remaining as a result have very little tendency to undergo further reaction.

SI unit of energy is Joules (J) and the metric unit of energy is calorie (cal).

99

2.11 Density

Density relates the mass of an object with its volume. Density is usually expressed in units as - Gram per cubic centimeter (g/cm3) for solids, and Gram per milliliter (g/mL) for liquids.

Density = Mass (g)

Volume (mL or cm3)

100

Osmium is a very dense metal. What is its density in g/cm3 if 50.00 g of the metal occupies a volume of 2.22 cm3?

1) 2.25 g/cm3

2) 22.5 g/cm3

3) 111 g/cm3

Learning Check

101

Place the mass of the osmium metal in the numerator of the density setup and its volume in the denominator.

D = mass = 50.00 g volume 2.22 cm3

calculator = 22.522522 g/cm3

final answer = 22.5 g/cm3

Solution

102

Density Using Volume Displacement

The volume of zinc is calculated from the displaced volume 45.0 mL - 35.5 mL = 9.5 mL = 9.5 cm3

Density zinc = mass = 68.60 g = 7.2 g/cm3

volume 9.5 cm3

103

What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL?

1) 0.2 g/ cm3 2) 6 g/cm3 3) 252 g/cm3

25 mL 33 mL

object

Learning Check

104

2) 6 g/cm3

Calculate the volume difference. 33 mL – 25 mL = 8 mL

Convert the volume in mL to cm3.

8 mL x 1 cm3 = 8 cm3

1 mL

Set up the density calculationDensity = mass = 48 g = 6 g = 6 g/cm3

volume 8 cm3 cm3

Solution

105

Sink or Float

Ice floats in water because the density of ice is less than the density of water. Aluminum sinks because it has a density greater than the density of water.

106

Which diagram correctly represents the liquid layers in the cylinder? Karo (K) syrup (1.4 g/mL), vegetable (V) oil (0.91 g/mL,) water (W) (1.0 g/mL)

1 2 3

K

K

W

W

W

V

V

V

K

Learning Check

107

1) vegetable oil 0.91 g/mL

water 1.0 g/mL

Karo syrup 1.4 g/mLK

W

V

Solution

108

Density represents an equality for a substance. The mass in grams is for 1 mL. For a substance with a density of 3.8 g/mL, the equality is:

3.8 g = 1 mL

For this equality, we can write two conversion factors.

Conversion 3.8 g and 1 mL factors 1 mL 3.8 g

Density as a Conversion Factor

109

The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane?

1) 0.614 kg

2) 614 kg

3) 1.25 kg

Learning Check

110

1) 0.614 kg

Unit plan: mL g kg

Equalities: density 1 mL = 0.702 g

and 1 kg = 1000 g

Setup: 875 mL x 0.702 g x 1 kg = 0.614 kg 1 mL 1000 g

density metric factor factor

Solution

111

If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given?

1) 0.548 L

2) 1.25 L

3) 1.83 L

Learning Check

112

1) 0.548 L

Unit Plan: g mL L

575 g x 1 mL x 1 L = 0.548 L 1.05 g 1000 mL

density metric factor factor

Solution

113

Density Using Volume Displacement

The volume of zinc is calculated from the displaced volume 45.0 mL - 35.5 mL = 9.5 mL = 9.5 cm3

Density zinc = mass = 68.60 g = 7.2 g/cm3

volume 9.5 cm3

114

A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 pound of aluminum, how many liters of aluminum (D=2.70 g/cm3) are obtained from the cans?

1) 1.0 L 2) 2.0 L 3) 4.0 L

Learning Check

115

1) 1.0 L

125 cans x 1.0 lb x 454 g x 1 cm3

21 cans 1 lb 2.70 g

x 1 mL x 1 L = 1.0 L 1 cm3 1000 mL

Solution

116

You have 3 metal samples. Which one will displace the greatest volume of water?

1 2 3

25 g of aluminum2.70 g/mL

45 g of gold19.3 g/mL

75 g of lead11.3 g/mL

Learning Check

117

1)

Calculate the volume for each metal and select the metal that has the greatest volume.

1) 25 g x 1 mL = 9.3 mL aluminum2.70 g

2) 45 g x 1 mL = 2.3 mL gold19.3 g

3) 75 g x 1 mL = 6.6 mL lead11.3 g

Solution

25 g of aluminum2.70 g/mL

118

2. 12 Specific Gravity

Specific Gravity (sp gr): density of a substance divided by the density of water at the same temperature. Specific Gravity is unitless. At normal temperature, the density of water is close to 1 g/mL. Thus, specific gravity of a substance at normal temperature is equal to the density.

Density of substance (g/ml)

Density of water at the same temperature (g/ml)Specific gravity =

119

The specific gravity of a liquid can be measured using an instrument called a hydrometer, which consists of a weighted bulb on the end of a calibrated glass tube, as shown in the following Fig 2.6. The depth to which the hydrometer sinks when placed in a fluid indicates the fluid’s specific gravity.

120

Learning Check

Corn oil has a density of 0.92 g/mL. What is the specific gravity of corn oil?

1) 0.92 2) 0.92 g 3) 1.1

121

Solution

Corn oil has a density of 0.92 g/mL. What is the specific gravity of corn oil?

1) 0.92

specific gravity = 0.92 g/mL = 0.92

1.00 g/mL

122

Learning Check

A bone sample has a mass of 52 g. If bone has a specific gravity of 1.8, what is the volume in milliliters of the bone sample?

1) 1.8 mL 2) 29 mL 3) 94 mL

123

Solution

2) 29 mLConvert the specific gravity to its densityusing the density of water1.8 x 1.00 g/mL = 1.8 g/mL

Use the density factor to cancel the initial unit.Volume = 52 g x 1 mL = 29 mL

1.8 g

124

Chapter Summary

Physical quantity, a measurable properties, is described by both a number and a unit.

Mass, an amount of matter an object contains, is measured in kilograms (kg) or grams (g).

Volume is measured in cubic meters (m3) or in liter (L) or milliliters (mL).

Temperature is measured in Kelvin (K) in SI system and in degrees Celsius (oC) in the metric system.

125

Chapter Summary Contd.

Measurement of small or large numbers are usually written in scientific notation, a product of a number between 1 and 10 and a power of 10.

A measurement in one unit can be converted to another unit by multiplying by a conversion factor.

Energy: the capacity to supply heat or to do work.

Potential energy – stored energy. kinetic energy – energy of moving particles.

126

Chapter Summary Contd. Heat: kinetic energy of moving particles in a

chemical reaction. Temperature: is a measure of how hot or cold an

object is. Specific heat: amount of heat necessary to raise

the temperature of 1 g of the substance by 1oC. Density: grams per milliliters for a liquid or

gram per cubic centimeter for a solid. Specific gravity: density of a liquid divided by

the density of water.

127

End of Chapter 2