Chapter 1
1.
First, download and start memorizing a list of polyatomic ions. There are more this year than
last year (This is AP after all). Make flash cards and work on them daily. You are not allowed to
forget them this year.
2. Atoms vs. Molecules
a. Atoms are the smallest unit of an element that maintains the properties of the element.
b. Molecules are discrete groups of atoms that are attached chemically to one another
i. Diatomic Molecule-molecules consisting of two of the same element
1. –Gens-Hydrogen, Nitrogen, Oxygen, and the Halogen group (group 7A)
ii. Ionic compounds can never be referred to as molecules because they are
merely a bunch of cations and anions arranged in a lattice, not a discrete group
of atoms
1. Ionic compounds are referred to as formula units, or a ratio of cations to
anions
3. A chemical reaction occurs when bonds are broken and reformed in a different arrangement
4. Laws vs. Theories
a. A law summarizes what happens.
i. Matter is neither created nor destroyed in a chemical reaction (statement)
b. A theory (model) is an attempt to explain why it happens.
i. In a chemical reaction atoms are rearranged into different compounds, not
changed into different atoms (explanation)
5. Nature of Measurement
a. Measurement - quantitative observation consisting of 2 parts
i. Part 1 – number
ii. Part 2 – scale (unit)
b. Examples:
i. 20 grams
ii. 6.63 × 10-34 Joule seconds
6. Uncertainty in Measurement
a. A digit that must be estimated is called uncertain.
b. A measurement always has some degree of uncertainty.
c. When measuring, one must always estimate one digit beyond the smallest marking on
the instrument
d.
e. The smallest marking on the buret is the tenth of a milliliter. Therefore, we must
estimate one place beyond that to the hundredth. Therefore the measurement as
indicated is 20.15mL
7. Accuracy vs. Precision
a. Accuracy—how close a measurement is to the actual value
b. Precision—how close a group of measurements are to one another
c. Look at this dartboard and determine whether each illustration shows accuracy,
precision, both or neither
d. Why is it incorrect to say that the results of a measurement were accurate but not
precise?
e. Answer on last page
8. Since there is always uncertainty in measurement, we must have a way of performing
calculations to include that uncertainty
a. Calculations cannot be more accurate than the least accurate measurement
9. Significant digits
a. Nonzero integers always count as significant figures.
i. 3456 has 4 sig figs.
b. Leading zeros do not count as significant figures.
i. 0.048 has 2 sig figs.
c. Captive zeros (zeros between significant figures) always count as significant figures.
i. 16.07 has 4 sig figs.
d. Trailing zeros are significant only if the number contains a decimal point.
i. 9.300 has 4 sig figs
ii. 150 has 2 sig figs.
e. Exact numbers have an infinite number of significant figures.
i. 1 inch = 2.54 cm, exactly so it could also be said that
1.000000000000000000000…inch=2.54000000000000000000000000000…cm
10. Calculations with significant figures
a. When adding or subtracting the answer cannot have more significant figures than the
measurement with the least decimal places
b. When multiplying or dividing the answer cannot have more significant figures than the
measurement with the least total significant figures
i. You have water in each graduated cylinder shown. You then add both samples
to a beaker.
1. How would you write the number describing the total volume?
2. What limits the precision of this number?
3. Answers on last page
Dimensional analysis:
1. Set up your dooflatchy (sp?)
2. Set up your units to cancel to achieve your desired units
3. Plug in numbers
4. Multiply the top numbers and divide the bottom
5. What data would you need to estimate the money you would spend on gasoline to
drive your car from New York to Chicago? Provide estimates of values and a sample
calculation.
6. See answers on last page
Temperature
1. F=(9/5)C+32
a. Room temperature is about 75°F. What is this in celsius?
2. K=C+273.15
a. What is the Fahrenheit temperature at absolute zero?
3. At what temperature does C = F?
4. See answers on last page
Density
1. D=m/v
a. A chemist, trying to identify the main component of a compact disc cleaning fluid, finds
that 25.00cm3 of the substance has a mass of 19.625g at 20°C. The following are the
names and densities of the compounds that might be the main component.
Chloroform
1.492g/cm3
Diethyl Ether
0.714g/cm3
Ethanol
0.789g/cm3
Isopropyl alcohol
0.785g/cm3
Toluene
0.867g/cm3
Which of these compounds is the most likely to be the main component of the compact disc
cleaner
2. Answers on last page
3. Classification of matter
a. The Three States of Water
b. The Organization of Matter
i. Sketch a magnified view (showing atoms/molecules) of each of the following:
1. a heterogeneous mixture of two different compounds.
2. a homogeneous mixture of an
element and a compound.
3. Answers at end
Answers to Practice Questions
Accuracy vs. Precision
Answers cannot be accurate without being precise because if all of the measurements are close
to the actual value, they will invariably be close to one another as well.
Significant Digits
2.81mL + 0.280mL = 3.09mL
Dimensional Analysis
We would need to know the miles, miles per gallon and and cost per gallon of gas
Distance = 791.0miles (Google it)
Miles per gallon = 19 mi/gal
Price of Gas = $3.31/gal
Temperature
75°F=(9/5)°C + 32 = 24°C
absolute zero=0 K
0K=TC + 273
TC=-273°C
TF=(9/5)(-273°C) + 32
TF=-459°F
TC=TF=x
x=(9/5)x +32
x=-40°
Density
d=m/v
d=19.625g/25.00cm3
d=0.7850g/cm3
Isopropyl alcohol is the main ingredient