1. Chemistry and Chemicals
Chemistry in Our Lives
Chemistry and Chemicals

2. What is chemistry? Chemistry is the study of substances in terms of
Composition What a material it made of
Structure How the elementary particles are put together
Properties The characteristics of the material
Reactions How it behave with other substances

3. Chemical reactions happen when
a car is started
tarnish is removed from silver
fertilizer is added to help plants grow
food is digested
electricity is produced from burning natural gas
rust is formed on iron nails

4. Everything in our lives from materials to life involve chemistry
glass (SiO2)n
metal alloys
chemically treated water
plastics and polymers
baking soda, NaHCO3
foods
fertilizers and pesticides
living beings

5. Chemicals in Toothpaste

6. The Scientific Method
The scientific method is the process used to explain observations in nature.
The method involves:
making observations
forming a hypothesis
doing experiments to test the hypothesis

7. Everyday Scientific Thinking
Observation: The sound from a CD in a CD player skips.
Hypothesis 1: The CD or player is faulty.
Experiment 1: When the CD is replaced with another one, the sound from the second CD is OK.
Hypothesis 2: The original CD has a defect.
Experiment 2: When the original CD is played in another player, the sound still skips.
Theory: The experimental results suggest that the original CD has a defect.

8. Units of Measurement

9. In chemistry:
quantities are measured
experiments are performed
results are calculated
use numbers to report measurements,
results are compared to standards.

10. In a measurement of the thickness
of the skin fold at the waist,
calipers are used.
A measuring tool is used to
compare some dimension
of an object to a standard.

11. In every measurement, a number must be followed by a unit to have any meaning.
Observe the following examples of measurements:
Number and Unit
m (meter)
L (liter)
lb (pound)
h (hour)

12. The Metric System (SI)
The metric system and SI (international system) are
related decimal systems based on 10
used in most of the world
used everywhere by scientists

13. Length
is measured using a meter stick
uses the unit meter
(m) in both the metric and SI systems

14. The unit of an inch
is equal to exactly
2.54 centimeters in
the metric system
1 in. = 2.54 cm

15. Volume
is the space occupied
by a substance
the unit of volume is the liter (L) in the metric system
1 L = 1.06 qt

16. is a measure of the quantity of material it contains
The mass of an object
is a measure of the quantity of material it contains
the unit gram (g) or kilogram (1000 g) is used
What is the difference between mass and weight?
Weight is the result of the action of gravity on mass. Your weight on the moon would be a lot less even though your mass would remain the same
Despite this important difference, we will use these two terms interchangeably

17. indicates how hot or cold a substance is
The temperature
indicates how hot or cold a substance is
the Celsius (C) scale is used in the metric system
the Kelvin (K) scale is also used
18 °C is 64 °F on this thermometer
On the C scale, the melting point of ice is 0 C and boiling point of water is 100 C
What is heat or cold? What does temperature really measure?

18. Time measurement
the unit second (s) is used in the metric system.
Time is based on an atomic clock that uses a frequency emitted by cesium atoms

19. Scientific notation
is used to write very large or very small numbers
the width of a human hair ( m) is written
8 x 10-6 m
a large number such as s is written
4.5 x 106 s

20. Scientific Notation
A number in scientific notation contains a coefficient and a power of 10.
coefficient power of ten coefficient power of ten
x x
To write a number in scientific notation, the decimal point is placed after the first digit.
The spaces moved are shown as a power of ten.
= x = x 10-3
4 spaces left spaces right

21. 10-3/105 =
10-8
102
10-3*105 = =
105 =

22. Measurements Definition of a significant figure:
What is the length of this piece of wood?
What is the first digit? Any uncertainty in the digit? 4
What is the second digit? Any uncertainty in this digit?
4.5
What is the third digit? Any uncertainty in this digit?
4.56
Definition of a significant figure:
Significant digits include all digits with no uncertainty plus one estimation

23. What is the length of the red line?
. l l l l l cm
What is the length of the red line?
1) cm
2) cm
3) cm
9.38, or 9.39, 9.40 is less likely

25. Number of Significant Figures
Measurement
38.15 cm
5.6 ft m in
1200 m 4 2 5 2 2

26. A. Exact numbers are obtained by
2. counting
3. definition
B. Measured numbers are obtained by
1. using some measuring tool

27. Classify each of the following as exact (E) or
measured (M) numbers. Explain your answer.
A. __ Gold melts at 1064 °C.
B. __ 1 yard = 3 feet
C. __ The diameter of a red blood cell is 6 x 10-4 cm.
D. __ There are 6 hats on the shelf.
E. __ The atom sodium has 11 protons and 12 neutrons.

28. Significant Figures In calculations:
Answers must have the same number of significant figures as the measured numbers.
Calculator answers must often be rounded off.
Rounding rules are used to obtain the correct number of significant figures.

29. Rounding Off
When the first digit dropped is 4 or less, the retained numbers remain the same.
To round to 3 significant figures
drop the digits 32 = 45.8
When the first digit dropped is 5 or greater,
the last retained digit is increased by 1.
To round to 2 significant figures
drop the digits 884 = 2.5 (increase by 0.1)

30. Multiplication and Division
When multiplying or dividing use
the same number of significant figures (SF) as the measurement with the fewest significant figures
Example:
x = =
4SFs SFs calculator SFs

31. Addition and Subtraction
When adding or subtracting, use
the same number of decimal places as the measurement with the fewest decimal places
one decimal place
two decimal places
26.54 calculated answer
final answer (with one decimal place)

32. For each calculation, round the answer to give the
correct number of decimal places.
A =
1) 257 2) 3)
B – 18.2 = 1) 2)
3) 40.7

35. 1m/100cm = 1; 1m/1000mm = 1 1 = 100cm/1m; 1 = 1000mm/1m An equality
states the same measurement in two different units
can be written using the relationships between two metric units
Example: 1 meter is the same as 100 cm and 1000 mm.
1 m = cm
1 m = mm
1m/100cm = 1; m/1000mm = 1
1 = 100cm/1m; = 1000mm/1m

36. volume has the dimensions of length cubed

37. Several equalities can be written for mass
1 kg = 1000 g
1 g = mg
1 mg = g

38. Some Common Equalities

39. An injured person loses 0. 30 pints of blood
An injured person loses 0.30 pints of blood. How many milliliters of blood would that be?
0.30pt*1qt/2pt = 0.15qt;
0.15qt*946mL/qt = mL; mL
0.30pt*2pt/1qt = 0.60pt2/qt

40. If a person weighs 200 pounds, how many kiograms does the person weight?
200 lb*1 kg/2.2 lb = 90.9 kg
200 lb*2.2 lb/1 kg = 440 lb2/kg

41. If the thickness of the skin fold at the
waist indicates an 11% body fat, how
much fat is in a person with a mass
of 86 kg?
11 % fat means 11kg/100kg body weight
86 kg x kg fat = 9.5 kg of fat
100 kg

42. Density Density compares the mass of an object to its volume
is the mass of a substance divided by its volume
Density expression:
D = mass = g or g = g/cm3
volume mL cm3

43. Osmium is a very dense metal. What is its density in g/cm3 if 50
Osmium is a very dense metal. What is its density in g/cm3 if 50.0 g of osmium has a volume of 2.22 cm3?
1) g/cm3
2) g/cm3
3) 111 g/cm3

44. The density of the zinc object can be calculated from its mass and volume.
d = 68.6g/( )mL; g/9.5 mL
d = 7.2 g/mL