Transcript Chemistry

Chemistry
1.B Fundamental
Quantitative
Relationships
Significant Digits
1. All numbers 1-9 are significant
235 = 3 significant figures
132.24 = 5 significant figures
 2. Leading zeros are not significant
.009 = 1 significant figure
 3. Captive zeros are significant
5005 = 4 significant figures
 4. Trailing zeros are significant if the number
contains a decimal point
157.00 = 5 significant figures.

Significant Figures in Addition and
Subtraction
The number of decimal places in the result
is the same as the least number of
decimal places used in the calculation
 12.33 + 2.1 + 3.087 = ?

Significant Figures in Multiplication
and Division
The number of significant figures in the
result is the same as the least number of
significant figures used in the calculation.
 5.65 X 1.3 = ?

When Both Exist
If you are working a problem that has
multiplication, division, addition, and
subtraction, then you must use your order
of operations. PEMDAS
 Practice: 3.43 X 2.36 + 4 =

SI Base Units


There are seven SI base units.
Quantity symbol name abbreviation
1. length
l
meter
m
2. mass
m
gram
g
3. time
t
second
s
4. temperature T
kelvin
K
5. amount of
a substance n
mole
mol
6. electric
current
I
ampere
A
7. luminous
intensity
Iv
candela
cd
Metric System and Prefixes
King Henry died by drinking chocolate milk.
 k
h
da
B
d
c
m
103 102 101
10-1 10-2 10-3

B = Base Unit (gram) (Liter) (meter)
Derived Units are any unit that uses a prefix.
(centimeter)
k = kilo
h = hecto da = deka
d = deci c = centi
m = milli
Metric Conversions
1 kg = ? g
 .3 m = ? cm
 100 kL = ? L
 .3g = ? hg
 12mL = ? kL
 12g = ? mg
 100 kL = ? hL

Derived Units
Derived units are formed from the
combination of SI base units
 Area = m2
 Volume = m3
 Density = kg/m3

Metric Volume Conversions
Volume = length X width X height (these
are all a measure of length which would
be in centimeters)
 Our volume conversion factor is
1 cm3 = 1 mL
 34.3 L = ? m3
 3.8 mm3 = ? mL

Scientific Notation
Any number 1000 or above needs to be
written in scientific notation.
23,000 = 2.3 X 104
 Any number at .001 or less needs to be
written in scientific notation.
.00786 = 7.86 X 10-3

Density
Density = mass
volume
What is the density of a 19.625g object with
a volume of 25.00 cm3?

Problem Solving
If water has a density of 1g/mL, what is
the mass of 150 mL of water?
 Kool-aid is approximately 39% sugar. If
the kool-aid has a density of 4.5g/mL,
determine the grams of sugar in 300.0mL
of kool-aid?

Temperature Conversions
TK = temperature in Kelvin
 TC = temperature in Celsius
 TF = temperature in Fahrenheit
 TC = (TF – 32) / 1.8
 TF = TC (1.8) + 32
 TK = TC + 273
 TC = TK - 273

Temperature Conversions
1.
 2.
 3.
 4.
 5.

67.°F = ? K
340.K = ? °C
46.°C = ? °F
587. K = ? °F
87.°F = ? °C
Accuracy and Precision
Accuracy = correctness; agreement of a
measurement with the true value
 Precision = reproducibility; degree of
agreement among several measurements.

Dimensional Analysis

A literal equation is one which is
expressed in terms of variable symbols
(such as d, v, and a) and constants (such
as g). Often in science and math you are
given an equation and asked to solve it for
a particular variable symbol or letter called
an unknown.
Dimensional Analysis
F = ma solve for a
 v = d/t solve for t
 ab = cd solve for c
 R = dh/a solve for d
 A = h(a+b) solve for b
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Scientific Method

The scientific method is a logical approach
to solving problems by observing and
collecting data, formulating hypothesis,
and formulating theories that are
supported by data.
Observing and Collecting Data
Observing is the use of the senses to
obtain information. Observation often
involves making measurements and
collecting data.
 That data may be descriptive (qualitative)
or numerical (quantitative) in nature.

Systems
Experimenting involves carrying out a procedure
under controlled conditions to make
observations and collect data. To learn more
about matter, chemist study systems.
 A system is a specific portion of matter in a
given region of space that has been selected for
study during an experiment or observation.
 When you observe a reaction in a test tube, the
test tube and its contents form a system.

Forming Hypothesis
As scientists examine and compare the data
from their own experiments, they attempt to
find relationships and patterns – in other words,
they make generalizations based on the data.
 Scientists use generalizations about the data to
formulate a hypothesis, or testable statement.
 The hypothesis serves as the basis for making
predications and for carrying out further
experiments.
 Hypothesis are often drafter as “if-then”
statements. The “then” part of the hypothesis is
a prediction that is the basis for testing by
experiment.

Testing Hypothesis
Testing a hypothesis requires experimentation
that provided data to support or refute a
hypothesis or theory.
 During testing, the experimental conditions that
remain constant are called controls and any
condition that changes is called a variable.
 If testing reveals that the predictions were not
correct, the hypothesis on which the predictions
were based must be discarded or modified.

Theorizing
When the data from experiments show that the
predictions of the hypothesis are successful,
scientists typically try to explain the phenomena
they are studying by constructing a model.
 A model in science is more than a physical
object, it is often an explanation of how
phenomena occur and how data and events are
related.
 Models may be visual, verbal, or mathematical

Theory
A theory is a broad generalization that
explains a body of facts or phenomena.
 Theories are considered successful if they
can predict the results of many new
experiments.

Experiments Involve Two Groups
Control – part of an experiment that is
the standard against which results are
compared.
 Receives no experimental treatment.
Testing fertilizer:
The plant without the fertilizer would be the
control because you would compare the
plant that was fertilized with the one
without it.

Variables
Variable is what you change in an
experiment.
 In a controlled experiment only one
condition is changed at a time.
 2 types of variable
Independent Variables
Dependent Variables

Independent Variable
The condition in an experiment that is
tested.
 The only factor that affects the outcome
of the experiment.
 In the case of using fertilizer, the
presence of fertilizer is the independent
variable.

Dependent Variable
The Dependent variable depends on the
affects of the independent variable.
 Fertilizer: The growth of the plant would
be the dependent variable because the
fertilizer (independent variable) caused
the change.

Dependent variables are graphed on the y-axis
 Independent variables are graphed on the x axis
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