This document provides an introduction to basic chemistry concepts including matter, mass, density, the metric system, and temperature measurement. It defines matter as anything that has mass and takes up space, and discusses common forms of matter like air. Density is introduced as the ratio of mass to volume. The metric system and common units are outlined. Finally, temperature measurement and different scales are described along with conversions between Celsius, Kelvin and Fahrenheit scales.

1. Introduction to
Chemistry:
Matter
Basic Chemistry
Chapter 2
Rev. 1/15/02

2. The study of matter is
central to the study of
chemistry.
Q. What is matter?
A. Matter is anything that …
… has mass,
… and takes up space.

3. What are some
things that are
matter?

4. If it’s not matter,
what is it?
Energy
Energy
Heat
Light Kinetic energy

5. Do things you cannot see
have mass?
What about air?
How would you experimentally
determine that air has mass?
A column of air 1 inch square at the
base and as tall as the atmosphere,
weighs 14.7 pounds at sea level.

6. Consider these statements:
The mass of the beaker is 215 grams.
The beaker weighs 215 grams.
What is the difference
between mass and weight?

7. Look at the difference
between a balance and a
spring scale.
A balance compares two masses
like a “see-saw”.
A spring balance requires a force
to stretch the spring.

8. That’s the answer.
Weight is a force.
To weigh something we must
exert an opposing force.
Mass is not a force, it is a
measure of the quantity of
matter.

9. Suppose, on Earth you weigh
60 kilograms. That means
that you will also have a
mass of 60 kilograms.
On the surface of the Earth, mass and
weight have the same numerical
value.
Note: 60 kilograms is about 130 pounds.

10. But, if you go to the moon…
Take a balance and a spring
scale.
Even though there is no air on the
moon, there is still gravity.
The gravity on the moon is 1/6th
that of Earth.

11. On the moon …
The balance will indicate
60 kilograms,
but the spring scale will indicate
10 kilograms …
because the force exerted by
gravity is 1/6 that of Earth’s.

12. The bottom line …
Scientists tend to use “mass”
and “weight” interchangeably,
even though they know the
difference.
We will too.
Just be sure you know the difference
when it shows up on a test.

13. Where will you weigh more?
(a) Mt. Everest
(b) Myrtle Beach
(c) The bottom of a South
African diamond mine

14. The Metric
System

15. What are the basic units of
mass, length, volume,
temperature and time in the
metric system?

16. The metric system …
Mass Gram g
Length Meter m
Volume Liter L
Temperature Kelvin K
Time Second s

17. What are the commonly
used metric prefixes?
Mega- x 106 megabyte, megohm
Kilo- x 103 kilometer, kilogram
Centi- x 10-2 centimeter
Milli- x 10-3 millimeter, milligram
Micro- x 10 -6
micrometer, microgram
Nano- x 10 -9
nanometer

18. What are the symbols for
the metric prefixes?
Mega- M - MB, MΩ
Kilo- k - km, kg
Centi- c - cm
Milli- m - mm, mg, mL
Micro- µ - µm, µg, µL
Nano- n - nm

19. Density

20. What is density?
Density is the
ratio of the mass m
of an object to D=
the volume of V
the object.
Typical units of density are
grams per milliliter, g/mL

21. Does the density of a
substance depend on the
amount of substance?
No. The ratio is a constant.
As you add more mass of the
substance, the volume
increases as well.

22. Does the density of a
substance depend on the
temperature of the substance?
Yes. But only slightly for solids
and liquids. As the temperature
changes, expansion and
contraction occurs, which changes
the volume slightly, but …

23. The density of a confined gas
changes dramatically as the
temperature changes…
… because the
volume of a gas
depends on the Gas
temperature. Cylinder with
movable piston hotplate

24. Develop a method to
measure the density of a
piece of metal.
What equipment will you need?
What data should you take?
How will you analyze the data?

25. Devise a method to measure
the density of a liquid.
What laboratory equipment will
you need?
What kind of data should
you take?
How will you analyze the data?

26. How can you
measure the
volume of an
odd-shaped
solid?

27. Hint:
Archimedes
Eureka!

28. Liquid Displacement
An object will
displace its own
volume of water.

29. Devise a method to
measure the density of a
metal cylinder
What equipment will you need?
What data should you take?
How will you analyze the data?

30. Measurements
Accuracy and
Precision

31. Consider four targets and
three shots on each:
Low Precision High Precision
Low Accuracy Low Accuracy
Low Precision High Precision
High Accuracy High Accuracy

32. Precision vs Accuracy
Precision – the
reproducibility of the
measurement
Accuracy – the closeness
to the correct answer

33. Precision is indicated by …
 An uncertainty in the measurement
5.4 +/- 0.2 mL
34.56 +/- 0.01 g
19.3 +/- 0.1 cm
 It wouldn’t make sense to write a
volume as 15.675 mL when the
graduated cylinder is only precise to
the nearest mL: +/- 1 mL

34. Precision is also indicated …
… by the number of significant
digits in a measurement.
14.7 has 3 significant digits
1004 has 4 significant digits
200. has 3 significant digits
0.0046 has 2 significant digits
204.70 has 5 significant digits

35. Rules for Significant Digits
1. All non-zero digits are significant.
2. Zeroes between non-zero digits are
significant.
3. Zeroes which are place holders are
not significant, unless otherwise
indicated.
4. Zeroes which indicate the level of
precision are significant.

36. Examples
a. 243.5 a. 4
b. 0.0405 b. 3
c. 1,900 c. 2
d. 100. d. 3
e. 0.00360 e. 3
f. 304.50 f. 5

37. Precision in calculations:
 The answer can have no more
precision that the least precise
factor.
 In other words: the answer has the
same number of significant digits as
the value with the lowest number of
significant digits.

38. Multiply 3.5 cm by 0.251 cm
to get the area.
The calculator gives 0.8785 cm2
But we write the answer as 0.88 cm2
3.5 has two significant digits, and
0.251 has three significant digits …
the answer can only have
two significant digits. 0.88 cm2

39. A student finds a side of a rectangle
to be 3.69 m and another student
finds the other side to be 12 m.
Find the area of the rectangle.
A=LxW
A = 3.69 m x 12 m
A = 44 m2
Not 44.28, since the answer can have
only two significant digits.

40. Do the following calculations and
express the answer to the correct
number of significant digits.
1. 45.3 x 0.0031 = 0.14
2. 0.0850 x 32.2 = 2.74
3. 65.0 / 20.30 = 3.20
4. (7.3 x 103)( 3.030 x 104) = 2.2 x 108
5. 360 / 12 = 30.

41. Temperature
Measurements

42. Temperature is a
measure of “how hot
or cold” something is.
How do we measure
temperature?

43. Thermometer
Temperature probe
Thermocouple
Color

44. Temperature Scales
K C F Boiling point
373 100 212 of water
Freezing point of water
273 0 32
(Melting point of ice)
Absolute zero
0 -273 -462 (Coldest possible temp.)

45. Temperature Conversions
K = C + 273
F = 1.8 C + 32

46. In later projects we will
study heat transfer,
conservation of energy,
and measure the specific
heat capacity of a metal.

47. Things to find out about:
 Temperature and heat changes
 The “Law of Conservation of Energy”
 Specific heat capacity
 The equation Q = mc∆T
 A procedure to measure the mass and
volume of a solid cylinder of metal.
 A procedure to measure the specific
heat capacity of the metal.

48. Next presentation:
Chpt 3 - Energy
Click on the link below:
Energy