BC Chemistry 11 - Chapter 1

Scientific method

a method of investigation involving observation and theory to test scientific hypotheses

Robert Boyle

pioneered the use of the scientific method; "first true scientist"

Steps in the scientific method

1. Observations
2. Hypothesis
3. Testing (experimentation)
4. Statement of a theory
Steps 1-3 are a repeating cycle.

Observation

noticing a change or occurrence; collecting data

Statement of a hypothesis

making an educated guess to explain why the observation occurred; stated in the format, "if _____, then ______"

Experimentation/testing

create an experiment to test your hypothesis (either prove or disprove); results tell you if the hypothesis needs adjusting and can restart the cycle of observation, hypothesis, testing.

Statement of a theory

after collecting enough data from a series of explanations, a coherent set of explanations (theory) may be deduced

Law

general statement of fact; a "what," not a why

Theory

explains the "why"; supported by coherent explanations

Scientific notation

method of representing numbers in exponential form

Mantissa

first portion of a value expressed in scientific notation; number between 1 and 10; "decimal portion"

Ordinate

second portion of a value expressed in scientific notation; base 10 raised to some power; "exponential portion"

Linear relationship

y = Kx

Inverse relationship

y = K/x

Exponential relationship

y = Kx^n

SI system

International System of Units; modern metric system

Base unit of length

metre (m)

Base unit of mass

kilogram (kg)

Base unit of time

seconds (s)

Base unit of electric current

ampere (A)

Base unit of temperature

kelvin (K)

Base unit of luminous intensity

candela (cd)

Base unit for amount of substance

mole (mol)

Base unit for area

square metre (m^2)

Base unit of volume

litre (L)

Accuracy

the agreement of a particular value with its true value

Precision

exactness of a measurement

Systematic error

a group of errors that consistently appears in the same direction

Random error

a group of errors that appear in different directions

Range uncertainty

an acceptable range of values within which the true value of a measurement falls; commonly presented using plus or minus notation

Absolute uncertainty

exactly how much higher or lower a measured value is than an accepted value

Percentage error

(measured value - accepted value) / accepted value x 100%

Significant figures

all of the certain figures plus the first uncertain (estimated) figure

Dimensional analysis

a method that allows you to easily solve problems by converting one unit to another through use of conversion factors

Conversion factor

fraction or factor written so that the denominator and numerator are equivalent values with different units

Defined values

accepted values that do not affect the number of sig figs in an answer

giga

G; 10^9

mega

M; 10^6

kilo

k; 10^3

hecto

h; 10^2

deca

da; 10^1

deci

d; 10^-1

centi

c; 10^-2

milli

m; 10^-3

micro

μ; 10^-6

nano

n; 10^-9

Derived unit

unit composed of more than one unit; example: km/h