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CHEMISTRY-CPCHAPTER 1
CHEMISTRY AND YOU
This chapter will introduce you to chemistry and the uses of chemistry in our world. You will
apply the scientific method to various problems and use experiments to prove hypotheses. You
will also learn the basic mathematical skills needed to succeed in chemistry.
is also known as the central science
• Chemists are employed in dozens of occupations
• Whatever your career choice is, chances are you will need some
knowledge of chemistry!!!!
The Scientific Method
Hypothesis: A Testable Prediction
• If…then… statement
• Narrow—tests one, and only one, thing
Example 1: The static on your radio increases right before it thunders during a storm.
Example 2: People who smoke cough more than people who don’t smoke.
Hypothesis: A Testable Prediction
• If…then… statement
• Narrow—tests one, and only one, thing
Example 3: You sneeze every time you visit your best friend’s house.
Example 4: On a cold morning, the air pressure in the tires of your car measures 34 psi. After several hours of high-speed driving, the pressure measures 38 psi.
EXPERIMENT
Variable: The factor being tested in an experiment
• Independent Variable: The factor that you change/adjust in the experiment
• Dependent Variable: The factor that changes due to changes in the independent variable.
EXPERIMENT
Control: Factor that responds in a predictable way to the experiment
– A control is what the rest of the experiment can be compared to
Constant: Factor(s) that do
not change during the
experiment.
• Independent Variable:• Dependent Variable:• Control:• Constant:
EXPERIMENT
Pea plant clones are given different amounts of water for a 3 week period. The first plant receives 400 mL a day. The second pea plant receives 200 mL a day. The third pea plant receives 100 mL a day. The fourth pea plant does not receive any extra water, the plant only receives natural ways of receiving water. The height of the pea plants is recorded daily.
• Independent Variable:• Dependent Variable:• Control:• Constant:
EXPERIMENT
You want to test which size ball is easiest to juggle. You test a baseball, a softball, a soccer ball and a basketball. You count the seconds you can continuously juggle each type of ball.
You want to determine which classroom is the hottest one in the school.
• Independent Variable:• Dependent Variable:• Control:• Constant:
• Data: Recorded Observations
• Graph: a visual representation of data
Graph: a visual Graph: a visual representation of datarepresentation of data
x-axis: the horizontal axisx-axis: the horizontal axis Independent Variable: The factor in the Independent Variable: The factor in the
experiment that the experimenter experiment that the experimenter changes.changes.
y-axis: the vertical axisy-axis: the vertical axis Dependent Variable: The factor that Dependent Variable: The factor that
changes due to changes in the changes due to changes in the independent variable.independent variable.
Y-a
xis
x-axis
Steps to GraphingSteps to Graphing
Numbering: Make sure the numbers Numbering: Make sure the numbers you put on the axes follow patterns.you put on the axes follow patterns. For example: 2, 4, 6, 8, 10 or 5, 10, 15, For example: 2, 4, 6, 8, 10 or 5, 10, 15,
20 or 0.1, 0.2, 0.3, 0.4 etc.20 or 0.1, 0.2, 0.3, 0.4 etc. Labeling: Make sure you label each Labeling: Make sure you label each
axis with a title and a unit and that axis with a title and a unit and that you title your graph.you title your graph.
TrendsTrends
Best Fit Line: A straight line that Best Fit Line: A straight line that goes through the center of most goes through the center of most points.points.
Trends cont.Trends cont.
Inversely Proportional: As one Inversely Proportional: As one variable increases, the other variable increases, the other variable decreases.variable decreases.
Trends in GraphingTrends in Graphing
Directly Proportional: As one Directly Proportional: As one variable increases/decreases the variable increases/decreases the other does the sameother does the same
Y-a
xis
x-axis
Example: Create a line graph of the following data: Mass (g)Mass (g) Volume Volume (cm(cm33))
2525 100100
3030 115115
4040 134134
5050 160160
5454 163163
Draw Conclusions
Theory: Explains
• States the “Why”
Law: States a Fact
• States the “What”
Base Units: The 7 metric units that SI is built upon
Physical Quantity Unit Name & Symbol Measured using…
Mass
Length
Time
Quantity
Temperature
Electric Current Ammeter
Luminous Intensity Photometer
NON-SI UNITS
Physical Quantity Unit Name Unit Symbol
Volume
Pressure
Temperature
Energy
Derived Units
1. Write the mathematical formula for the quantity.
2. Replace the formula with units and simplify.
Density
Density = Mass Volume
METRIC CONVERSIONS
METRIC PREFIXESPREFIX ABBREVIATION UNIT EQUALITY
mega-
kilo-
deka-
BASE UNIT
deci-
centi-
milli-
micro-
nano-
pico-
DIMENSIONAL ANALYSIS
• What is a conversion factor equal to?
• How do you use conversion factors?
Steps to Dimensional Analysis
1. Start with what you know (number and unit).
2. Times a line.
3. Add a conversion factor so that units cancel and what you are looking for is on top of the ratio.
4. Check your answer.
DIMENSIONAL ANALYSIS
Uncertainty in Measurements
Why are measurements uncertain? Precision of instrumentation varies Human error
Reading Measurements The number of digits you should write
when writing down a measurement depends on the instrumentation you are using.
You should always include a number and a unit when writing down a measurement
When determining a measurement include all the digits you know for certain plus 1 more digit.
Precision Also called reproducibility or repeatibility Measurements are close to each other (getting
the same measurements each time)
Accuracy
Measurements are close to the actual value
Graduated Cylinder
Put the cylinder flat on the table and read at the bottom of the miniscus (bubble)
Triple Beam Balance
OPENERWith your partner, make the following measurements. Be sure
to make the measurements to the proper # of digits. Be sure to include units for all measurements. Write your answers on a sheet of paper and have Ms. Wack check your answers. All materials are in the back of the classroom.
The volume of water in the 100 mL and 10 mL graduated cylinders.
The length of the paper clip. The mass of a 100 mL beaker.
ROUNDING The first significant digit is the first nonzero
number. Count the appropriate # of sig figs, if the
next number is 5 or greater, round the last number up 1. If not, do nothing. Examples:
2.3344(1)1.029 (3)0.00234(2)
SIGNIFICANT FIGURES
The certain digits and the estimated digit of a measurement.
All the known digits of a measurement and the one estimated digit.
SIGNIFICANT FIGURES1. All nonzero numbers are significant.
123 = _____ sig figs
2. All zeroes at the beginning are not significant.0.0025 = _____ sig figs
3. Zeroes between 2 nonzero digits are significant.5007= ______ sig figs
4. Zeroes at the end of a number are only significant if the number contains a decimal point.470 = ____ sig figs, 470.0 = ___ sig figs, 0.00470 = ____ sig figs
5. In scientific notation, all numbers in the coefficient are significant.2.020 x 104 = ____ sig figs
SIGNIFICANT FIGURESEasier Rule: To count significant figures, if there is
a decimal, count all digits including and after the first non-zero
number. If there is not a decimal, start counting at the first
non-zero number but do not count zeroes at the end of the
number.
3.3333 = ______ sig figs 2000.0 = ____ sig figs
3023 = ____ sig figs 0.216 = ____ sig figs72800 = ____ sig figs 0.009030 = ____ sig figs
Round each of the following numbers to 3 significant figures.a) 3.3333 d) 0.009030
b) 3023 e) 0.21653
c) 0.3287 f) 1.99999
SIGNIFICANT FIGURES IN CALCULATIONSMultiplication/Division: The measurement with the
smallest number of significant figures determines how many
significant figures are allowed in the final answer.
Addition/Subtraction: The measurement with the smallest
number of decimal places determines how many decimal
places are allowed in the answer.
SIGNIFICANT FIGURES IN CALCULATIONS0.3287 g x 45.2 g =
0.258 mL 0.36105 mL =
68.32 ns x 1.001 ns x 0.00367 ns =
8.85 cs 333.2 cs =
10 s 5 s =
800.0 mm x 200.00 mm x 10.0 mm =
Scientific Notation
A number is written in 2 parts. The first part is a number between 1 & 10 The second part is a power of ten
Exponent Positive exponents represent numbers
greater than 1 Negative exponents represent numbers less
than 1
Scientific Notation To convert a number to scientific notation:
Count how many places the decimal place must be moved to make the number a number between 1 & 10 (the coefficient) The number of spaces the decimal moved is the value of the
exponent If you moved the decimal to the right, the exponent is negative If you moved the decimal to the left, the exponent is positive Write: Coefficient x 10exponent
To convert a number from scientific notation to regular notation: If the exponent is positive, move the decimal in the coefficient
the number of spaces indicated by the exponent to the right If the exponent is negative, move the decimal in the coefficient
the number of spaces indicated by the exponent to the left.
Scientific Notation Example 1: Express each of the following in
scientific notation.8960 = 36,000,000 =
0.00023 = 0.000 000 025 3 =
Example 2: Express each of the following numbers in regular notation.4.563 x 107 = 2.53 x 10-3 =
6.805 x 108 = 1.33450 x 10-7 =
Scientific Notation
A number is written in 2 parts. The first part is a number between 1 & 10 The second part is a power of ten
Exponent Positive exponents represent numbers
greater than 1 Negative exponents represent numbers less
than 1
Calculating in Scientific Notation(Do not change the numbers out of scientific notation when calculating)
(5.5 x 106) x (1.111 x 10-1) =
(6.23 x 103) x 1 3.33 x 102
(6.026 x 1023) x (2.5 x 102)
(9.896 x 10-34) (3.311 x 10-24) =