John Dalton, 1766-1844

Marie Curie, 1867-1934

Antoine Lavoisier, 1743-1794

Joseph Priestly, 1766-1844

Dmitri Mendeleev, 1834-1907

What is Matter?

Matter: Anything that occupies space and has mass

Energy: Ability to do work, accomplish a change

Physical States of Matter

Gas: Indefinite volume, indefinite shape, particles far away from each other

Liquid: Definite volume, indefinite shape, particles closer together than in gas

Solid: Definite volume, definite shape, particles close to each other

Properties of Matter

Property: Characteristic of a substance

Each substance has a unique set of properties identifying it from other substances.

Intensive Properties: Properties that do not depend on quantity of substance

Examples: boiling point, density

Extensive Properties: Properties that depend on or vary with the quantity of substance

Examples: mass, volume

Physical Properties: Properties of matter that can be observed without changing the composition or identity of a substance

Example: Size, physical state

Chemical Properties: Properties that matter demonstrates when attempts are made to change it into new substances, as a result of chemical reactions

Example: Burning, rusting

Changes in Matter

Physical Changes: Changes matter undergoes without changing composition

Example: Melting ice; crushing rock

Chemical Changes: Changes matter undergoes that involve changes in composition; a conversion of reactants to products

Example: Burning match; fruit ripening

Classifying Matter

Pure substance: Matter that has only 1 component; constant composition and fixed properties

Example: water, sugar

•Element: Pure substance consisting of only 1 kind of atom (homoatomic molecule)

Example: O2

•Compound: Pure substance consisting of 2 or more kinds of atoms (heteroatomic molecules)

Example: CO2

Mixture: A combination of 2 or more pure substances, with each retaining its own identity; variable composition and variable properties

Example: sugar-water

•Homogenous matter: Matter that has the same properties throughout the sample

•Heterogenous matter: Matter with properties that differ throughout the sample

Solution: A homogenous mixture of 2 or more substances (sugar-water, air)

Measurement Systems

Measurement: Determination of dimensions, capacity, quantity or extent of something; represented by both a number and a unit

Examples: Mass, length, volume, energy, density, specific gravity, temperature

Mass vs. Weight

Mass: A measurement of the amount of matter in an object

Weight: A measurement of the gravitational force acting on an object

Density: mass divided by volume; d = m/v

Specific gravity: density of a substance relative to the density of water

English System Units: Inch, foot, pound, quart

Metric System: Meter, gram, liter

Unit of Length

Meter = basic unit of length, approximately 1 yard

1 meter = 1.09 yards

Kilometer = 1000 larger than a meter

Centimeter = 1/100 of a meter

100 cm = 1 meter

Millimeter = 1/1000 of a meter

1000 mm = 1 meter

Unit of Mass

Gram: basic unit of mass

454 grams = 1 pound

Kilogram: 1000 times larger than a gram

1 Kg = 2.2 pounds

Milligram: 1/1000 of a gram

Unit of Volume

Liter: basic unit of volume

1 Liter = 1.06 quarts

1 Liter = 10 cm x 10 cm x 10 cm

1 liter = 1000 cm3

1 ml = 1 cm3 (1 cc)

Unit of Energy

Joule: Basic unit of energy

calorie: amount of heat energy needed to increase temperature of 1 g of water by 1oC

1 cal = 4 joules

Nutritional calorie = 1000 calories = 1 kcal = 1 Calorie

Units of Temperature

Fahrenheit: -459oF (absolute zero) - 212oF (water boils)

Celsius: -273oC (absolute zero) - 100oC (water boils)

Kelvin: 0K (absolute zero) - 373 K (water boils)

Different Temperature Scales

Converting Celsius and Fahrenheit:

oC = 5/9 (Fo - 32) oF = 9/5 (oC) +32

Converting Celsius and Kelvin:

oC = K - 273 K = oC + 273

Scientific Notation and Significant Figures

Scientific notation: a shorthand way of representing very small or very large numbers

Examples: 3 x 102, 2.5 x 10-4

The exponent is the number of places the decimal must be moved from its original position in the number to its position when the number is written in scientific notation

If the exponent is positive, move the decimal to the right of the standard position

Example: 4.50 x 102 450

3.72 x 105 372,000

If the exponent is negative, move the decimal to the left of the standard position

Example: 9.2 x 10-3 .0092

Practice with Scientific Notation

50,000 = 5.0 x 104 300 =

.00045 = 4.5 x 10-4 .0005 =

3.00 x 102

5 x 10-4

Significant Figures

Significant Figures: Numbers in a measurement that reflect the certainty of the measurement, plus one number representing an estimate

Example: 3.27cm

Rules for Determining Significance:

All nonzero digits are significant

Zeroes between significant digits are significant

Example: 205 has 3 significant digits

1,006 has

10,004 has

4 sig. figs.

5 sig. figs.

Leading zeroes are not significant

Example: 0.025 has 2 significant digits

0.000459 has 3 significant digits

0.0000003645

Trailing zeroes are significant only if there is a decimal point in the number

Examples: 1.00 has 3 significant figures

2.0 has 2 significant digits

20 has

1500

1.500

4 sig. figs.

1 sig. fig.

2 sig. figs.

4 sig. figs.

Calculations and Significant Figures

Answers obtained by calculations cannot contain more certainty (significant figures) than the least certain measurement used in the calculation

Multiplication/Division: The answers from these calculations must contain the same number of significant figures as the quantity with the fewest significant figures used in the calculation

Example: 4.95 x 12.10 = 59.895

Round to how many sig. figs.?

Final answer:

3

59.9

Addition/Subtraction: The answers from these calculations must contain the same number of places to the right of the decimal point as the quantity in the calculation that has the fewest number of places to the right of the decimal

Example: 1.9 + 18.65 = 20.55

How many sig. figs.required?

Final answer:

Rounding Off

Rounding off: a way reducing the number of significant digits to follow the above rules

1

20.6

Rules of Rounding Off:

Determine the appropriate number of significant figures; any and all digits after this one will be dropped.

If the number to be dropped is 5 or greater, all the nonsignificant figures are dropped and the last significant figure is increased by 1

If the number to be dropped is less than 5, all nonsignificant figures are dropped and the last significant figure remains unchanged

Example: 4.287 (with the appropriate number of sig. figs. determined to be 2)

4.287 4.3

We only use significant figures when dealing with inexact numbers

Exact (counted) numbers: numbers determined by definition or counting

Example: 60 minutes per hour, 12 items = 1 dozen

Inexact (measured) numbers: numbers determined by measurement, by using a measuring device

Example: height = 1.5 meters, time elapsed = 2 minutes

Classify each of the following as an exact or a inexact number.

A. A field is 100 meters long.

B. There are 12 inches in 1 foot.

C. The current temperature is 20o Celsius.

D. There are 6 hats in the closet.

Practice:

Inexact

Inexact

Exact

Exact

Calculating Percentages

percent = “per hundred”

% = (part/total) x 100

Example: 50 students in a class, 10 are left-handed. What percentage of students are lefties?

% lefties = (# lefties/total students) x 100

= 10/50 x 100

= .2 x 100

= 20%

Practice Using and Converting Units in Calculations

Sample calculation: Convert 125m to yards.

•Write down the known or given quantity (number and unit)

125 m

• Leave some blank space and set the known quantity equal to the unit of the unknown quantity

125 m = yards

• Multiply the known quantity by the factor(s) necessary to cancel out the units of the known quantity and generate the units of the unknown quantity

125 m x 1.09 yards/1 m = yards

•Once the desired units have been achieved, do the necessary arithmetic to produce the final answer

125 x 1.09 yards /1 = 136.25 yards

•Determine appropriate amount of sig. figs. and round accordingly

Fewest sig. figs. in original problem is 3 (from 125), so final answer is 136 yards

Accuracy vs. Precision

Error: difference between true value and our measurement

Accuracy: degree of agreement between true value and measured value

Uncertainty: degree of doubt in a measurement

Precision: degree of agreement between replicated measurements