Chapter 3

Scientific Measurement

Ch 3.1 The Importance of Measurement

Ch 3.1 The Importance of Measurement

Qualitative Measurement – measurement that gives descriptive nonnumeric results

Example: Feel some ones head to see if they are running a fever or not

Quantitative Measurement – measurement that gives definite usually numeric results

Example: Measure some ones temperature with a thermometer

Scientific Notation

Used to write small or large numbers

N x 10n

N = a number between 1 and 10

n = a positive or negative integer

Scientific Notation

Mass of an atom of gold0.000000000000000000000327g

3.27 x 10-22g

Number of hydrogen atoms in 1g602000000000000000000000

6.02 x 1023 atoms

Coefficient

Scientific notation has three parts to it: the coefficient, base, and exponent

Scientific Notation: Multiply and Divide

Multiply coefficients and add exponents(3.0 x 104) x (2.0 x 102) = 6.0 x 106

Divide coefficients and subtract exponents(3.0 x 104) / (2.0 x 102) = 1.5 x 102

Scientific Notation: Addition and Subtraction

Make the exponents the same, then add or subtract

3.0 x 104 + 2.0 x 102 =

300.0 x 102 + 2.0 x 102 = 302.0 x 102

Chapter 3.2 Uncertainity

Accuracy and Precision

Accuracy – how close a measurement is to the true value of the quantity measured

Precision – how closely two or more measurements of the same quantity agree with one another

Accuracy and Precision

A student was asked to measure the length of the hallway. He came up with the following lengths.

10.2m, 10.1m, 10.2m

The actual length was 12.5m.

How would you describe his results?

Accuracy and Precision

A student was asked to determine the mass of a beaker. She came up with 34.8g, 34.7g and 34.7g.

The actual mass was 34.8g.

How would you describe her results?

Percent Error

% Error = accepted value – experimental value x 100

accepted value

The correct answer

Your answer

The correct answer

Percent Error

A student was asked to determine the mass of a beaker. She came up with an average mass of and 34.7g.

The actual mass was 34.8g.

What is the percent error?

34.8 g –34.7 g x 100 = 0.287 % Error

34.8

Significant Figures

Abbreviation: sig fig

Why are sig figs so IMPORTANT?

Significant Figures

1) Any digit that is not zero is significant

24.7 meters 3 sig figs

0.743 meters 3 sig figs

74 grams 2 sig figs

Significant Figures

2) Zeros between nonzero digits are significant

7003 mL 4 sig figs

40.7 cm 3 sig figs

1.5035 g 5 sig figs

Significant Figures

3) Zeros to the left of the first nonzero digits are not significant

0.0071 km 2 sig figs

0.420 g 3 sig figs

0.00009999 L 4 sig figs

Significant Figures

4) If a number is greater that 1, then all the zeros written to the right of the decimal point count as significant

43.00 m 4 sig figs

1.0100 mg 5 sig figs

9.00 cL 3 sig figs

Significant Figures

5) Numbers without a decimal, the trailing zeros may or may not be significant. It will depend on other information in the problem.

5,000 1 or 4 sig figs

68,900 3 or 5 sig figs

52,010,000 4 or 8 sig figs

Significant Figures

6) Unlimited significant figures when:

- Counting an exact number (whole number only) such as number of people in the class

- Exactly defined quantities

60 minutes = 1 hour

Significant Figures for Calculations

Addition and Subtraction: The answer can not have more digits to the right of the decimal point than either original number. (Least number of decimal places)

400.567 + 21.0 =

421.567

421.6

68.892 – 48.47 =

20.422

20.42

Significant Figures for Calculations

Multiplication and Division: The number of significant figures in the final product or quotient is determined by the original number with the smallest number of significant figures.

12,003 x 45 = 1,525÷ 30.1 =

540,135 50.66445183

540,000 50.7

Chapter 3.3 SI Units

International System of Units

From the French:

Le Systeme International d’Unites

SI Units

Symbol Name Quantity

m meter length

g gram mass

Pa pascal pressure

K kelvin temperature

mol mole amount of a substance

J joule energy, work, quantity of heat

s second time

SI Units (continued)min minute time

h hour time

d day time

y year time

L liter volume

ppm parts per million concentration

M molarity solution concentration

u atomic mass unit atomic mass

Prefixes with SI UnitsPrefix Symbol Meaning

tera- T 1,000,000,000,000 or 1012

giga- G 1,000,000,000 or 109

mega- M 1,000,000 or 106

kilo- K 1,000 or 103

hecto- H 100 or 102

deca- D 10 or 101

BASE m, L, g, ….

Any base unit

deci- d 1/10 or 10-1

centi- c 1/100 or 10-2

milli- m 1/1,000 or 10-3

micro- μ 1,000,000 or 10-6

nano- n 1,000,000,000 or 10-9

pico- p 1,000,000,000,000 or 10-12

How to remember the basic metric prefixes?

Mnemonics :These stand for the Metric prefixes and base unit.

kilo hecto deca base deci centi milli

Kittens Hate Dogs Because Dogs Cant Meow

Kangaroos Hop Down My Driveway Christmas Morning

Kings Hate Dragons Because Dragons Can’t Make Money

King Henry Died Bloated Drinking Chocolate Milk

Kangaroos Hop Down Mountains Drinking Chocolate Milk

giga mega kilo hecto deca BASE deci centi milli micro nano pico

King Henry Danced Merrily Down Center Main Meeting Nice People

Great Mighty King Henry Died By Drinking Chunky Milk

Good Models Know How Dunkin Donuts Can Make U Not Petit

Chapter 3.4 Density

Density = Mass / Volume

d = m/v

1 g/cm3 = 1 g/ml

1 mL = 1 cm3

Density Column

Chapter 3.5 Temperature Scales0C = K – 273

K = 0C + 273

Freezing 00C = 273K

Boiling1000C = 373K

Absolute ZeroO K

Temperature Scales