Chapter 2 Notes

Chapter 2

Logical approach to solve problems

Observe, collect data, formulate hypothesis, test hypothesis, formulate theories supported by data

Steps may vary

Using your senses to collect information

May make measurements

May collect data

Record of facts

Logical interpretation based on knowledge and experiences

In lab, you note observations, not inferences

Inferences may be used in writing conclusions (lab reports)

Let’s test your observation skills…….

1. Are there cars parked on the sides of the road?

2. What color is the pickup truck driving on the road?

3. Are there any minivans around?4. What does the blue sign say?5. What’s the speed limit?6. Are there any pedestrians?

On the next slide, state whether the statement is an observation or an inference.

1. There is a representation of a face on one side of the coin.

2. The Latin word "Dei" means "God."3. The coin was made by deeply religious people.4. The date 1722 is printed on one side of the coin.5. The coin was made in 1722.6. The face on the coin is a representation of the

nation's president.

Do you see former President Bill Clinton and Al Gore?

Actually, it’s Clinton’s face twice with 2 different hair cuts!

Hint: There are 3 images.1. An old

lady

2. A young woman

3. A man with a big brown mustache

They are the SAME length!

A Duck, Bunny, or BOTH?

This image contains a picture and a word. Do you see both of them?

Your Your brainbrain!!

Your right brain tried to say the color,

but your left brain was reading the word.

They are all the same height!

The Landscape of Faces

How about now?

Testable statement

Basis for making predictions and for carrying out further experiments

“If-then” statements

Model◦ More than just a physical object◦ Explanation of how phenomena occur and how

data or events are related◦ Ex: atomic model of matter (atoms)

Theory◦ Broad generalization that explains facts or

phenomena

Quantitative information

Represents quantities

◦ Quantity:

Something that has magnitude, size, or amount

Not the same as a measurement

Defined in terms of standards of measurement

Have constant value, easy to preserve and reproduce, practical in size

SI Base Units

Quantity Quantity Symbol

Unit Name Unit Abbreviation

Length l meter m

Mass m kilogram kg

Time t second s

Temperature T kelvin K

Amount of substance

n mole mol

Electric current

I ampere A

Prefix Unit Abbreviation

Meaning/Example

mega M 1Mm = 1,000,000m

kilo k 1km = 1,000m

hecto h 1hm = 100m

deka da 1dam = 10m

deci d 1m = 10dm

centi c 1m = 100cm

milli m 1m = 1,000mm

micro μ 1m = 1,000,000μm

nano n 1m = 1,000,000,000nm

pico p 1m = 1,000,000,000,000pm

SI Prefixes

Derived SI UnitsQuantity Quantity

SymbolUnit Unit

AbbreviationDerivation

Area A Square meter m2 length x width

Volume V Cubic meter m3 length x width x height

Density D Kilograms per cubic meter

kg/m3 mass / volume

Molar Mass M Kilograms per mole kg/mol mass / amount of substance

Concentration

c Moles per liter M amount of substance /

volume

Molar Volume Vm Cubic meters per mole

m3/mol volume / amount of substance

Energy E joule J force x length

Measure of a quantity of matter Often confused with weight

Weight◦ measure of the gravitational pull on matter

Amount of space occupied by an object

Derived SI unit is cubic meters (m3)

The ratio of mass to volume

(Mass divided by volume)

Characteristic physical property of a substance

Does NOT depend on size of sample

Can be used as a property to identify a substance

Conversion factor- a ratio derived from the equality between two different units that can be used to convert from one unit to the other.

Accuracy◦ Closeness of measurement to the correct or

accepted value

Precision◦ Refers to the closeness of a set of measurements

of the same quantity made in the same way

100 Value

Value - Value error Percent

accepted

alexperiment accepted

Rules:1. Zeros appearing between non-zero digits are

significant.2. Zeros appearing in from of all non-zero digits

are not significant.3. Zeros at the end of a number and to the right of

a decimal point are significant.4. Zeros at the end of a number but to the left of a

decimal point may or may not be significant. If a zero has not been measured or estimated, but is

just a placeholder, it is not significant. A decimal point placed after zeros indicates that they

are significant.

When you add or subtract decimals, the answer must have the same number of digits to the right as there are in the measurement having the fewest digits to the right of the decimal.

For multiplication and division, the answer can have no more sig. figs. than are in the measurement with the fewest number of sig. figs.