Chapter 1 Elements and Measurements You are responsible for all sections in this chapter.

Elements and MeasurementsYou are responsible for all

sections in this chapter

Periods: 7 horizontal rows.

Groups: 18 vertical columns.International standard: 1-18US system: 1A-8A, 1B-8B

Some Chemical Properties of the Elements

Physical Properties: Characteristics that do not involve a change in a sample’s chemical makeup.

Chemical Properties: Characteristics that do involve a change in a sample’s chemical makeup.

The Metric System (SI)The metric system or SI (international

system) is

• a decimal system based on 10.

• used in most of the world.

• used everywhere by scientists.

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Experimentation and Measurement

All other units are derived from these fundamental units

Système Internationale d´Unités

Measuring MassMass: Amount of matter in an object.

Matter: Describes anything with a physical presence—anything you can touch, taste, or smell.

Weight: Measures the force with which gravity pulls on an object.

Measuring Temperature

TF = 1.8 TC + 32

TC = (TF – 32)

1.8

K = °C + 273.15

Scientific Notation

Scientific Notation

• is used to write very large or very small numbers.

• for the width of a human hair of 0.000 008 m is written 8 x 10-6 m.

• of a large number such as 4 500 000 s is written 4.5 x 106 s.

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Accuracy, Precision, and Significant FiguresSignificant figures: The number of

meaningful digits in a measured or calculated quantity. They come from uncertainty in any measurement.

Generally the last digit in a reported measurement is uncertain (estimated).

Exact numbers and relationships (7 days in a week, 30 students in a class, etc.) effectively have an infinite number of significant figures.

length = 1.74 cm

0 1 2 43cm

1.7 cm < length < 1.8 cm

Accuracy, Precision, and Significant Figures

Rules for counting significant figures (left-to-right):

1. Zeros in the middle of a number are like any other digit; they are always significant.

4.803 cm 4 sf

2. Rules for counting significant figures (left-to-right):

Zero at the beginning of a number are not significant (placeholders).

0.00661 g 3 sf or 6.61 x 10-3 g

Accuracy, Precision, and Significant Figures

Rules for counting significant figures (left-to-right):

3. Zeros at the end of a number and after the decimal point are always significant.55.220 K 5 sf

4. Zeros at the end of a number and after the decimal point may or may not be significant.34,2000 ? SF

Rounding NumbersIf the first digit you remove is 5 and there are

more nonzero digits following, round up.

5.664 525 = 5.665

If the digit you remove is a 5 with nothing following, round down. 5.664 525 = 5.664 52

Multiplication and Division

When multiplying or dividing

• the final answer must have the same number of significant figures as the measurement with the fewest significant figures.

Example:

110.5 x 0.048 = 5.304 = 5.3 (rounded)

4 SF 2 SF calculator 2 SF

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Addition and Subtraction

When adding or subtracting

• the final answer must have the same number of decimal places as the measurement with the fewest decimal places.

25.2 one decimal place

+ 1.34 two decimal places 26.54 calculated answer 26.5 final answer with one

decimal place

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Calculations: Converting from One Unit to AnotherDimensional analysis: A method that

uses a conversion factor to convert a quantity expressed in one unit to an equivalent quantity in a different unit.

Conversion factor: States the relationship between two different units.

original quantity x conversion factor = equivalent quantity

Conversion FactorsA conversion factor is• obtained from an equality.

Equality: 1 in. = 2.54 cm

• written as a fraction (ratio) with a numerator and denominator.

• inverted to give two conversion factors for every equality. 1 in. and 2.54 cm

2.54 cm 1 in.

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Conversion Factors in a ProblemA conversion factor

• may be obtained from information in a word problem.

• is written for that problem only.

Example : The cost of one gallon (1 gal) of gas is $4.29.

1 gallon of gas and $4.29$4.29 1 gallon of gas

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Example:

How many ounces are in 1.0 kg?

How many in3 in 1.5 m3

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Examples

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?

density =volume

mass

solids- cm3

liquids- mLgases- L

Typical volume units

Osmium is a very dense metal. What is its density in g/cm3 if 0.11 lb of osmium has a volume of 2.22 ml?

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