Chemistry:
The Study of Change
Chapter 1
• Health and Medicine Sanitation systems; Vaccines and antibiotics
• Energy and the Environment; Fossil fuels; Solar energy; Nuclear energy
• Materials and Technology
Polymers, ceramics, liquid crystals; Room-temperature superconductors; Molecular computing?
•Food and Agriculture Genetically modified crops; “Natural” pesticides; Specialized fertilizers
The Study of Chemistry
Physical Characteristics of Rust:
•a solid
•orange color,
•forms on the surface of a metal
Chemical Characteristics of Rust:
•forms on a metal containing iron exposed to air
•the chemical formula for Rust is Fe2O3
•there are 3 atoms of oxygen for 2 atoms of iron
Classifications of Matter
Matter is anything that occupies space and has mass.
Substance is a form of matter that has a definite composition and distinct properties.
1.1
Salt dissolved
In water
sand
In water
Sugar, water
Carbon
Homogenous mixture – composition of the mixture is the same throughout.
Heterogeneous mixture – composition is not uniform throughout.
A compound is a substance composed of atoms of two or more elements chemically united in fixed proportions.
Compounds can only be separated into their pure components (elements) by chemical means.
Ammonia (NH3)
Water (H2O)
Glucose (C6H12O6)
Memorize these Elements
H, Li, C, N, O, F, Na, Mg, K, Ca, Al, S, P, Cl, Fe, Cu, Ag, Au, Ni, Pb, Hg
1.2
The Three States of Matter
Solid: very organized; particles close together
Liquid: medium organization; some space between particles
Gas: disorganized; mostly empty space
Physical or Chemical properties of Matter
A physical change does not alter the composition or identity of a substance.
ice melting
sugar dissolving in water
A chemical change alters the composition or identity of the substance(s) involved.
hydrogen burns in air to form water
Measurement: International System of Units (SI)
1.3
Measuring Liquid Volume
1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3
1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3
1 L = 1000 mL = 1000 cm3 = 1 dm3
1 mL = 1 cm3
Volume – SI derived unit for volume is cubic meter (m3)
Other properties:
Extensive: depends on the amount of matter present
Example: mass
the weight of two marbles is the sum of both masses
Example: volume
one cup of water added to one cup of water = 2 cups
Intensive: the amount of matter is not considered
Example: temperature
the temperature of two cups of water, each at 25°C will be 25°C when combined
Example: density
the density of one gallon of water is 1.00 g/mL;
the density of one cup of water is 1.00 g/mL
1.4
Density – SI derived unit for density is kg/m3
mass
m
density = volume
d=
v
1 g/cm3 = 1 g/mL = 1000 kg/m3
* A piece of platinum metal with a density of 21.5 g/cm3 has a volume of 4.49 cm3. What is its mass?
m
m=dxV
m = 21.5 g/cm3 x 4.49 cm3 = 96.5 g
d=
v
Temperature scales:
SI: Kelvin K
oF
US: Fahrenheit
Common: Celsius oC
K = 0C + 273.15
273 K = 0 0C
373 K = 100 0C
0F
=
0C
=
9
5
5
x 0C + 32
x (0F – 32)
9
0F
*Convert 172.9
to degrees Celsius.
5
0C =
x (0F – 32) = 5/9 (172.9 – 32) = 78.3oC
9
1.5
Handling Numbers
568.762
N is a number between 1 and 10
n is a positive or negative integer
N x 10n
Scientific Notation
move decimal left
n>0
move decimal right
0.00000772
n<0
568.762 = 5.68762 x 102
0.00000772 = 7.72 x 10-6
Addition or Subtraction
1.
Write each quantity with the same exponent n
4.31 x 104 + 3.9 x 103 =
2.
Combine N1 and N2
4.31 x 104 + 0.39 x 104 =
3.
The exponent, n, remains the same
4.70 x 104
Multiplication
1.
Multiply N1 and N2
(4.0 x 10-5) x (7.0 x 103) = (4.0 x 7.0) x (10-5+3) = 28 x 10-2 = 2.8 x 10-1
2.
Add exponents n1 and n2
Division
1.
Divide N1 and N2
8.5 x 104 ÷ 5.0 x 109 = (8.5 ÷ 5.0) x 104-9 = 1.7 x 10-5
2.
Subtract exponents n1 and n2
Significant Figures
- The meaningful digits in a measured or calculated quantity
- The last digit is uncertain; 6.0±0.1ml
• Any digit that is not zero is significant
1.234 kg
• Zeros between nonzero digits are significant
606 m
• Zeros to the left of the first nonzero digit are not significant
2.0 mg
2 significant figures
0.00420 g
3 significant figures
4 significant figures
3 significant figures
0.08 L
1 significant figure
How many significant figures are in each of the following measurements?
24 mL
3001 g
2
4
0.0320 m3
3
6.40 x 104 molecules
3
5600 kg
4
1.6
Addition or Subtraction
The answer cannot have more digits to the right of the decimal point than any of the original numbers.
89.332
3DP
1DP
+ 1.1
one significant figure after decimal point
round off to 90.4
90.432
2DP
3.70
1DP
two significant figures after decimal point
4DP -2.9133
0.7867
round off to 0.79
2DP
Multiplication or Division
The number of significant figures in the result is set by the original number that has the smallest number of
significant figures
4.51 x 3.6666 = 16.536366 = 16.5
3 sig figs
round to
3 sig figs
3 sig figs
6.8 ÷ 112.04 = 0.0606926 = 0.061
2 sig figs
round to 2 sig figs
2 sig figs
Exact Numbers
The average of three measured lengths; 6.64, 6.68 and 6.70?
6.64 + 6.68 + 6.70
= 6.67333 = 6.67 = 7
Because 3 is an exact number
3
1.7
Example 1.5
(a) 11,254.1
(b)
66.59
(c) 8.16 m
(d) 0.0154 kg / 88.3 mL
0.1983
3.113
= 0.00017440… = 0.000174 kg/mL
+
x 5.1355
11,254.2983
63.477
41.90568
= 11,254.3 g
= 63.48 L
= 41.9 m
(e) 2.64 x 103 + 3.27 x 102 = 2.64 x 103 + 0.327 x 103 = (2.64 + 0.327) x 103 = 2.967 x 103 = 2.97 x 103
Accuracy – how close a measurement is to the true value
Precision – how close a set of measurements are to each other
If you are 100 lbs, 5 measurements:
(a) 99.9, 99.8, 100.1, 100.2, 99.9 ---- accurate and precise
(b) 120.0, 119.9, 119.8, 120.1, 120.0 ----- precise bot not accurate
(c) 80.2, 70.3, 90.0, 85.0, 110.0 – neither precise nor accurate
Dimensional Analysis Method of Solving Problems
How many mL are in 1.63 L?
Conversion Unit 1 L = 1000 mL
1000 mL
1.63 L x
= 1630 mL
1L
The speed of sound in air is about 343 m/s. What is this speed in miles per hour?
conversion units
meters to miles
seconds to hours
1 mi = 1609 m
1 min = 60 s
1 hour = 60 min
343
m
s
x
1 mi
1609 m
x
60 s
1 min
x
60 min
1 hour
mi
= 767
hour
Example 1.8
1 kg = 1000 g, 1 g = (1 / 1000) kg
1 cm = 10-2 m, so 1 cm3 = (10-2) 3 m3 = 10-6 m3
kg
1
cm3
0.808 g/cm3 =
g
1
x
x
x
x
x
0.808
cm3 1000
g 10-6
m3
= 808 kg/m3