Intro to Chemistry

Why Care?

Chemistry is Everywhere

• Data analysis• Matter• Structure of atom• Elements• Bonding• States of matter• Chemical reactions• Reaction rates• Thermochemistry

Break it Down

• With a MODEL– A replica or description

designed to show the structure or workings of an object, system, or concept

– Physical or mathematical

• SI System – MKS system

• Meters, kilograms, seconds

– CGS• Centimeters, grams,

seconds

Standards of Length, Mass and Time

Base Units and Derived Units

• Base units – quantity measured from natural phenomenon

• Derived units – mathematically manipulated base units – Area– Volume– density

What is the SI base unit for length?

1. Inch2. Kilometer3. Meter4. Mile

1 2 3 4 5

Scientific Notation

• Used to obtain correct # of sig figs for really big and small numbers

• Check out your resources

• To convert large # to small #, move decimal to left

• To go from small to big, move decimal to right

How to do it on Calculator• Use the EE button• 5E5 means 5x105

Let’s Do Some Now

Dimensional Analysis

• Dimension has a specific meaning – it denotes the physical nature of a quantity

• Dimensions are denoted with square brackets– Length [L]– Mass [M]– Time [T]

• But WHAT’S A DIMENSION? And how many are there?

Dimensional Analysis

Conversion Factors

• Metric prefixes– Briefly

• Conversion factors– Equal to each

other– 2.54 cm/1 in– 1 kilometer/1000

meters

• Use conversion factors when going from one unit to another

Dimensional Analysis

• Refers to the base quantities that make up the value– Dimension of area: Length squaredL2

– Dimension of velocity: length/time L/T– Dimension of force: (mass)(acceleration)ML/T2

• Helps you determine if your relationships are correct

Unit conversion

Now You Practice

• Convert each of the following length measurements to its equivalent in meters

• 1.1 cm• 76.2 pm• 2.1 km• 0.123 Mm

Taking measurements

• Take measurement to first known value and one estimated value

• This is the basis for the concept of significant figures (SigFig)

Significant Figures

• Rules of thumb– In multiplication, division, addition or subtraction

• The result should have only as many digits as the number with the least amount of significant figures used

• For adding and subtracting, the number of decimal places is the important consideration

• For multiplying and dividing, the number of significant figures is the important consideration

– Keep an extra digit in calculations and then round off for the final result

– Rounding• If the next digit is < 5 (i.e. 0,1,2,3,4), then round down• If the next digit is ≥ 5 (i.e. 5,6,7,8,9), then round up

Rules• Zeros between other nonzero digits are

significant– 50.3 m (3) 3.0025 s (5)

• Zeros in front of nonzero digits are NOT significant– 0.892 m (3) 0.0008 s (1)

• Zeros that are at the end of a number and also to the right of a decimal are significant– 57.00 g (4) 2.000000 kg (7)

• Zeros at the end of a number are not significant but to the left of the decimal are significant if they have been measured or are the first estimated digit. Otherwise they are not.– 20 cm (1 or 2)

Calculators

• They don’t care about sigfigs

Accuracy and Precision

Thanks and Have a Great Day!