Honors Chem. Ch.2 Measurements and Calculations

6 steps

How many steps are in the scientific method?

Scientific method

is a logical approach to solving problems by collecting data, formulating hypothesis, testing hypothesis, and coming up with theories that are supported by the data

observation

recognition of a problem

hypothesis

proposed explanation of an observation

experiment

an organized procedure used to test a hypothesis

control

standard for comparison

Independent variable

a variable that changes unrelated to other factors

dependent variable

a variable we manipulate, changes, on purpose

Analyze data

looks for patterns in experimental data

quantitative

numbers

qualitative

observation

conclusion

presents the finding of the experiment, what the data shows, the hypothesis, and whether or not it was correct (supported) or incorrect (negated)

Communicating results/sharing with peers

when scientists collaborate and communicate, They increase the likelihood for a successful outcome

SI base units

the universal single measurement system that has 7 base units

SI prefixes

are often added to the name of base units to represent quantities that are much larger/smaller than the base unit

Volume

is the amount of space occupied by an object

Density

is the mass of a substance divided by its volume

conversion factor

a ratio that is equal to one

Accuracy

refers to how close the measurements are to the correct accepted value

Precision

refers to how close a set of measurements made in the same way as each other

Percentage error

used to be able to compare the experimental value with correct accepted value

meter;m

length

gram;g

mass

mole;mol

moles

second;s

time

kelvin(Celsius),k(C)

Temperature

liter,L

Volume

Candela,Cd

Light intensity

ampere, A

Electric Current

problem statement

is a question that compares variables

true

a hypothesis is a statement NOT a question

variables

any conditions that change during the experiment

bar graph

a _____ is used to show relationships between groups (used to compare two things)

circle graph

used to show how a part of something relates to the whole

line graph

is used to show continuing data; how one thing is affected by another

Theory

is a broad generalization that explains a body of facts or phenomena

models

is an explanation of why an event occurs and how data and events are related

%error= experimental value-accepted value over accepted value x 100%

percentage error formula

%error is positive

if accepted value is less than the experimental value

%error is negative

if the accepted value is greater than the experimental value

accuracy

refers to how close the measurements is to the correct or accepted value

precision

refers to how close a set of measurement made in the same way are to each other

density=mass/ volume or D=m/V

density formula

volume

is the amount of space occupied by an object

L x W x H

Formula of Volume

si prefixes

are often added to the names of base units to represent quantities that are much larger/ smaller than the base units

giga

G

mega

M

Kilo

K

hecto

H

deca

da

deci

d

centi

c

milli

m

nano

n

pico

p

quantity

is something that has magnitude, size, or amount

SI system

the universal single measurement system that has 7 base units