Chapter 1 Chemistry: The Study of Change
The Scientific Method
Three Levels of Studying Chemistry
Representation
Observation
Interpretation
Observations
Data
Qualitative
Quantitative
Hypothesis
Law
Theory
Chapter 1 Chemistry: Matter and Measurement -1
Classification
of Matter
Matter - anything that occupies space and has mass.
Substance is a form of matter that has a definite (constant) composition
and distinct properties.
Mixture - a combination of two or more substances in which the
substances retain their distinct identities.
Homogenous mixture - composition is the same throughout.
Heterogeneous
mixture - composition not uniform
Elements and Compounds
Elements - a substance that cannot be separated into simpler substances
by chemical means.
chemical symbols:
H, O, N, C, Li, Cl, Br, Hg, Au
See Periodic Table
Chapter 1 Chemistry: Matter and Measurement -2
Compound - substance composed of two or more elements chemically
united in fixed proportions.
Classification of Matter
Matter
Mixtures
Homogeneous
Mixtures
Separation by Physical Methods Pure
Substances
Heterogeneous
Mixtures
Compounds
Separation
by chemical
methods
Three States of Matter
1.4 Properties of the Elements
Intensive Properties
Extensive Properties
Physical Properties
Chemical Properties
Chapter 1 Chemistry: Matter and Measurement -3
Elements
Physical Properties
Temperature
Color
Melting point
Electrical conductivity
Amount
Odor
Solubility
Hardness
Chemical Properties
Rusting (of iron)
Combustion (of coal)
Tarnishing (of silver)
Hardening (of cement)
Physical and Chemical Changes
Physical changes
Chemical changes (reactions)
Measurement
Macroscopic - direct observation
Microscopic - indirect observation
International
System of Units, SI
Physical Quantity
Name of Unit
Abbreviation
Mass
kilogram
kg
Length
meter
m
Temperature
Kelvin
K
Amount of substance
mole
mol
Time
second
s
Electric Current
ampere
A
Luminous intensity
candela
cd
Prefixes
Chapter 1 Chemistry: Matter and Measurement -4
Prefix
Abbreviation
Meaning
Example
Giga
G
109
Gigabyte
Mega
M
106
Megawatt
Kilo
k
103
Kilogram
Deci
d
10-1
Deciliter
Centi
c
10-2
Centimeter
Milli
m
10-3
Millimeter
Micro
µ
10-6
micrometer
Nano
n
10-9
Nanometer
Pico
p
10-12
Picometer
Femto
f
10-15
femtosecond
Scientific Notation: Dealing with very large and very small numbers.
Units
Measuring Mass
Mass?
Chapter 1 Chemistry: Matter and Measurement -5
Measuring Length
Measuring Temperature
Fahrenheit
Celsius scale – based on freezing point (O °C) and boiling point (100 °C)
of water.
Kelvin scale – 0 K is –273.15 °C (absolute zero)
K = °C + 273.15
The Celsius and Kelvin scales have equal sized units.
5
°C = (°F − 32 )
9
9
°F = °C + 32
5
Derived Units: Measuring Volume
Chapter 1 Chemistry: Matter and Measurement -6
Derived Units: Measuring Density
Accuracy, Precision, and Significant
Figures in Measurement
Chapter 1 Chemistry: Matter and Measurement -7
Guidelines to significant figures in a measured quantity
1.
Nonzero digits are always significant
457 cm (3 sig. figs)
2.
Zeros between nonzero digits are always significant
1005 kg (4 sig. figs)
3.
2.5 g (2 sig. figs)
1.03 cm (3 sig. figs)
Zeros at the beginning of a number are never significant; they
merely indicate the position of the decimal point
0.02 g (1 sig. figs)
4.
0.0026 cm (2 sig. figs)
Zeros that fall both at the end of a number and after a decimal point
are always significant
0.0200 g (3 sig. figs)
5.
3.0 cm (2 sig. figs)
When a number ends in zero but contains no decimal point, the
zeros may or may not be significant
130 cm (2 or 3 sig. figs)
10,300 g (3, 4, or 5 sig. figs)
The use of exponential notation (Appendix A) avoids possible ambiguity
seen in the last example
Using exponential notation 10,300 g can be written
1.03 × 10 4 g
(three significant figures)
1.030 × 104 g
(four significant figures)
Chapter 1 Chemistry: Matter and Measurement -8
1.0300 × 10 4 g
(five significant figures)
Rounding Numbers: Significant
Figures in Calculations
In multiplication and division, the result must be reported with the same
number of significant figures as the measurement with the fewest
significant figures.
1.
If the leftmost digit to be removed is less than five, the preceding
number is left unchanged.
Rounding 7.248 to 2 sig. figs gives 7.2
2.
If the leftmost digit to be removed is 5 or greater, the preceding
number is increased by 1.
Rounding 4.735 to three significant figures gives 4.74
Rounding 2.376 to two significant figures gives 2.4.
In addition and subtraction, the result cannot have more digits to the
right of the decimal point than any of the original numbers.
20.4
1.322
83
104.722
Calculations:
Round off to 105
Converting
from One Unit to Another
Chapter 1 Chemistry: Matter and Measurement -9
The Factor-Label Method of Solving Problems
Dimensional analysis method
Conversion factors (see back inside cover)
Summary of Dimensional Analysis
In using dimensional analysis to solve problems, we will always ask three
questions:
1.
What data are we given in the problem?
2.
What quantity do we wish to obtain in the problem?
3.
What conversion factors do we have available to take us from the
given quantity to the desired one?
Convert 5.4 in into cm with the correct number of significant figures.
Chapter 1 Chemistry: Matter and Measurement -10
Aspirin has a density of 1.40 g/cm3. What is the volume (in cubic
centimeters) of an aspirin tablet weighting 250 mg? Of a tablet weighing
500 lb?
Chapter 1 Chemistry: Matter and Measurement -11