Transcript final review

Sem 1 Final Review
Chapters 1- 5
States of Matter
• Fixed = solid
• Variable shape = liquid
• Variable shape and volume = gas
Physical vs. Chemical
• Physical properties can be measured
without changing the substance
• Examples: color, shape, mass, density,
conductivity, malleability, melting point
• Chemical properties are only apparent
when the substance reacts
• Examples: reacts with oxygen, burns,
rusts, decomposes when heated
Elements vs. Compounds
• Elements have only one type of atom –
they are listed on the periodic table
• Examples: Ag, Cu, Br2, F2, S8
• Compounds have different types of atoms
combined as molecules
• Examples: CO, H2O, NH3
Pure vs. Mixture
• Pure substances are either elements (all
same atom) or compounds (all the same
molecules)
• Mixtures must have more than one
substance.
Homogeneous vs.
Heterogeneous
• Homogeneous means the ‘same’
throughout
• All pure substances are homogeneous.
• SOLUTIONS are homogeneous mixtures.
• Examples: air, kool-aid, steel (Fe and C)
• Many mixtures are heterogeneous,
different areas have different properties
• Example: chicken noodle soup
Periodic Table
• Families (columns) have similar
characteristics
• Important families: alkali metals, alkaline
earth metals, halogens, noble gases
• Most elements are metals because most
elements have 1,2, or 3 outer electrons
• Metals tend to lose electrons to become
cations (+) when they form compounds
Diatomic Elements
• When these elements are alone and
uncharged, they will exist as molecules
H2
N2 O2 F2
Cl2
Br2
I2
Atomic Structure
• The nucleus of an atom is made of protons
and neutrons
• It is positively charged and VERY small.
• The electrons surround the nucleus and
create an electron cloud.
• The electron cloud is negatively charged
and 10000x bigger than the nucleus.
• Remember – you are mostly
empty space.
Atomic notation
The bottom number is the ATOMIC NUMBER = number of
protons.
The top number is the MASS NUMBER = protons and
neutrons
Elements with the same # of protons but different # of
neutrons are called ISOTOPES.
65
30
66
30
Zn
Zn
Zn-65
p = 30 n = 35 e = 30
Zn-66
p = 30 n = 36 e = 30
Ionic Compounds
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Write the correct formula for these:
Sodium sulfide
Magnesium oxide
Iron(III) nitrate
Aluminum phosphate
Ionic Compounds
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Write the correct formula for these:
Sodium sulfide = Na2S
Magnesium oxide = MgO
Iron(III) nitrate = Fe(NO3)3
Aluminum phosphate = AlPO4
Naming Compounds
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Write the name for these:
AlCl3
CrCl3
PCl3
BeI2
Cu(NO3)2
NO2
Naming Compounds
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Write the name for these:
AlCl3 = aluminum chloride
CrCl3 = chromium(III) chloride
PCl3 = phosphorous trichloride
BeI2 = beryllium iodide
Cu(NO3)2 = copper(II) nitrate
NO2 = nitrogen dioxide
Scientific Notation
• Good notation has only one number
before the decimal.
• All of the digits shown in scientific notation
are significant digits.
Decimal notation
Scientific notation
0.003505
3.505x10-3
25500
2.55x104
4200
4.2x103
0.0250
2.50x10-2
Significant Figures
• Measure all the marks and estimate one
digit between the marks.
• When you write the number, the last digit
is always a ‘guess’ because its your
estimate.
• All the known digits and your estimate are
the ’significant figures’
Counting Sig Figs
• All non-zeros are sig figs (123456789)
• Zeros at the beginning are never sig figs
0.00345
• Zeros bewteen numbers are always sig
figs
42005
• Zeros at the end are only sig figs if there is
a decimal point 3700 3700. 25.00
Using Sig Figs
• Sig figs allow us to round our answers
correctly
• When multiplying or dividing, round to the
smallest number of sig figs in the problem
525.55 x 16.2 = 8513.91 (round to 3 sig figs) 8510
• When adding or subtracting, round to the
smallest number of places after the
decimal (or the last column with sig figs for
ever number in the problem.)
525.55 + 16.2 = 541.75 (round to 1 decimal) 541.8
Dimensional Analysis
• Use equalities to convert numbers/solve
problems
• Set-up so the units cancel
• Multiply the tops, divide by the bottoms
How many seconds in 3.25 hours?
3.25 hr
X
60 min
1 hr
X
60 sec = (3.25)(60)(60) = 11700 sec
(1)(1)
1 min
Density
• Density = mass/volume
• The density of water is 1 g/mL
• Things that are more dense than water will
sink in water. If there are less dense they
will float on water.
Put these objects in the cylinder of water.
floats
D = 0.80 g/mL
1.0 g/mL
D = 1.25 g/cm3
sinks