Unit 1Intro to Chemistry and

Measurement

Chemistry IMr. Patel

SWHS

Topic Outline

• Learn Major Elements and Symbols• Intro to Chemistry (1.1, 1.2)• Significant Figures (3.1)• Measurement (3.1, 3.2)• Factor-Label Method of Conversions (3.3)

Intro to Chemistry

• Matter – anything that has mass and occupies space

• Chemistry – study of the composition of matter and the changes it undergoes

Intro to Chemistry

• Chemistry affects all aspects of life and other natural events!– Food Digestion– Leaves changing colors– Muscle contraction– Driving cars

Intro to Chemistry

• Five different areas or branches of chemistry

Organic Chemistry

• Study of all chemicals containing carbon

Inorganic Chemistry

• Study of chemicals that do not contain carbon

Biochemistry

• Study of processes that occur in living things

Analytical Chemistry

• Study that focuses on the composition of matter

Physical Chemistry

• Area that deals with the rate, mechanism, and energy transfer of chemistry

Types of Research

• Pure Chemistry – increase chemical knowledge

• Applied Chemistry – goal oriented

History of Chemistry

• Alchemy - change other metals to gold

• Lavoisier – Father of Modern Chemistry– Observation to measurement

Scientific Method

Significant Figures

• Sometimes we estimate numbers– If we measure between 9.8 and 9.9, we may say it

is 9.85.– We know that the 9 and 8 are definite; 5 is

estimated.• Discuss accuracy/precision later• Significant Figures – the digits from a

measurement that are known precisely plus an estimated digit

Rules for Counting Significant Figures

1. Every nonzero number is significant (sig.) – 1453 = 4 sig fig

2. Zeros between nonzero numbers are sig.– 300205 = 6 sig fig

3. Leftmost zeros in front of nonzeros are NOT sig. (placeholders)– 0.000356 = 3 sig fig

4. Zeros at end of a number are significant if there is a decimal point– 900.00 = 5 sig fig

5. Zeros at the end of a number are NOT significant if there is NOT a decimal point– 900 = 1 sig fig

6. Counting numbers and exact numbers have an infinite number of sig. figures– 23 people = infinite

Significant Figure – My Way

• Just think about the Atlantic and Pacific Oceans in relation to the USA

• Is the decimal point Absent (Atlantic) or Present (Pacific)

• Choose direction: Start at that “ocean” and come toward the USA (number)

• Stop at first NONZERO number• Count that number and everything after

Sig Fig Practice

• 5005• 63.207• 9050• 3.00• 0.00509• 0.00003• 7000

• 4 sig fig• 5 sig fig• 3 sig fig• 3 sig fig• 3 sig fig• 1 sig fig• 1 sig fig

Calculations with Sig. Fig.

• When ROUNDING, choose the number of sig figs needed. Look at the number to the right of last sig fig to determine if you need to round.

• Special rules for adding/subtracting and multiplying/dividing

Adding/Subtracting Sig Fig

• Answer to addition or subtraction problem should contain the same number of decimal places (not sig fig) as original number with the least decimal places.

• Ex: 12.52 + 349.0 + 8.24– Sum is 369.76– But 349.0 has only ONE decimal place– ANSWER is 369.8

Sig Fig Add/Subtract Practice

• 61.2 + 9.35 + 8.6• 9.44 – 2.11• 1.36 + 10.17• 34.61 – 17.3• 14.2 + 8.73 + 0.912

• 79.2• 7.33• 11.53• 17.3• 23.8

Multiply/Divide Sig Fig

• Answer to multiplication or division problem should contain the same number of significant figures as original number with the least significant figures.

• Ex: 7.55 x 0.34– Product is 2.567– But 0.34 has only TWO sig figs– ANSWER is 2.6

Sig Fig Multiply/Divide Practice

• 2.10 x 0.70• 2.4526 / 8.4• 8.3 x 2.22• 8432 / 12.5• 22.4 x 11.3 x 5.2

• 1.5• 0.29• 18• 675• 1300

Measurement

• Measurement – quantity with a number and unit

• Accuracy – how close you are to the true value

• Precision – how close your measurements are to one another

Scientific Notation

• Used for very large or very small numbers• Converts a single number to a product of two

numbers– Ex: 8000 8 x 103

– Ex: 0.234 2.34 x 10-1

Scientific Notation Practice

1. 2522. 1250003. 0.003054. 0.00000000548

1. 2.52 x 102

2. 1.25 x 105

3. 3.05 x 10-3

4. 5.48 x 10-9

International System of Units (SI)

• Five SI base units: – meter (length)– kilogram (mass)– Kelvin (temperature)– Second (time)– Mole (amount)

Metric Conversions

Kilo - k 103 1000

BASE 100 1

Deci - d 10-1 0.1

Centi - c 10-2 0.01

Milli - m 10-3 0.001

Factor-Label Method

• Write down starting and ending unit• Write all relevant conversion factors• Cancel units to get to end unit– To cancel a unit, the unit must be on the top and

bottom

Conversion Examples