Unit1 part1

Unit 1
INTRODUCTION TO CHEMISTRY

The Scope of Chemistry
Why is it important to study chemistry?
We’ve got all the right elements!

What is chemistry?
Chemistry is the study of matter. Matter is anything
that has mass and takes up space.
What are some examples of matter?
What are some examples of non-matter?

Chemistry: the central science
Science is called the central science because it is fundamental to the
understanding of the other sciences.
The five traditional areas of study of chemistry are:
• Inorganic chemistry:
•Organic chemistry:
•Biochemistry:
•Analytical chemistry:
•Physical chemistry:

Pure or applied chemistry?
Pure chemistry
Applied

Chemistry and You
Why study chemistry?

Chemistry is useful in:
o Explaining the natural world: Chemistry helps us
understand concepts in our daily life.
Examples:
It explains why apples pieces turn brown upon exposure to
air.
It explains why sugar dissolves faster in warm water versus
cold water.
It explains how different grades of gasoline cause an effect
on your car engine.

Chemistry is useful in:
o Preparing for a career:
oBeing an informed citizen:

Thinking like a scientist
The word chemistry comes from ALCHEMY.
Alchemy was practiced in China and India as
early as 400B.C. Arabs brought it to Spain and
from there it quickly spread to other parts of
Europe.
Alchemists main goal was to convert other
metals into gold.
Although they did not succeed. They developed
important tools and techniques.

Alchemy and Chemistry
Alchemists developed equipment we use
until today:

Lavoisier: law of conservation
of matter
• Lavoisier helped transform chemistry
from the science of observation to the
science of measurement.
• developed a balance that could
measure mass to the nearest 0.00005
grams.
• his experiments explained how
materials burn

The Scientific Method
1. Observation: using your senses to obtain information, asking experts on
the field
2. Hypothesis: proposed explanation to an observation. It must be
answered by a test. Only one possible answer must be tested at a time.
3. Experiment: procedure used to test a hypothesis
Independent variable: the variable that you change (factor you are testing)
Dependent variable: your result
4. Theory: well-tested explanation for a hypothesis (test supported
explanation)
5. Scientific law: statement that summarizes the results of many
experiments.

Gold medal: 9.63s Silver medal: 9.75s Bronze medal: 9.79s
Measurements

Chemistry also requires making accurate and
often very small measurements.
A measurement is a quantity that has both a
number and a unit.
Examples of measurements:

Yao Ming is 7ft 6 in. tall
In 1933, the lowest temperature
recorded in Siberia was:
-90° Fahrenheit (-68°Celsius)

Scientific Notation
In chemistry, you will often encounter
very large or very small numbers.
◦ A single gram of hydrogen, for example, contains
approximately 602,000,000,000,000,000,000,000
hydrogen atoms.
It is easier to work wth numbers written in scientific
notation.

Scientific Notation
an expression of numbers in the
form m x 10n, where m is equal to
or greater than 1 and less than 10,
and n is an integer.
7.3 x 1014
coefficient 10 raised to
a power

Scientific Notation
A positive exponent indicates how
many times the coefficient must be
multiplied by 10.
A negative exponent indicates how
many times the coefficient must be
divided by 10.

Scientific Notation
It can be written in scientific
notation as
6.02 x 1023
The coefficient in this number is
6.02. The power of 10, or
exponent, is 23.

Practice:
a. 827,000,000
b. 0.0037
c. 1,202,000,000,000,000

◦ In chemistry, the meanings of accuracy and
precision are quite different.
◦ Accuracy is a measure of how close a
measurement comes to the actual or true value
of whatever is measured.
◦ Precision is a measure of how close a series of
measurements are to one another, irrespective
of the actual value.
Accuracy and Precision

To evaluate the accuracy of a measurement,
the measured value must be compared to
the correct value.
To evaluate the precision of a measurement,
you must compare the values of two or
more repeated measurements.

Good Accuracy,
Good Precision
Poor Accuracy,
Good Precision
Poor Accuracy,
Poor Precision

Accuracy, Precision, and
Error

◦accepted value: correct value
for the measurement based on
reliable references
◦experimental value: the value
measured in the lab
Determining Error

◦The percent error of a measurement is the
absolute value of the error divided by the
accepted value, multiplied by 100%.
Determining Error
Percent error =
error
accepted value
100%x

Unit1 part1

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