Today is Friday (!),
February 19th, 2016
Pre-Class:
Today we are reviewing for our exam.
The test will be on mixtures, elements,
substances, density, sig figs, dimensional
analysis (unit conversions), basic atomic
structure, and a tiny bit of atomic history.
Today’s Agenda
• Review Game
Review Game Rules
• I will ask a question to the class.
• Each participant (that’s you) writes down the
answer silently.
– Not each group…each individual.
• After a few moments, I will say, “Compare
answers.”
• Each of you will look at what the other wrote.
Review Game Rules
• Did you each get the right answer?
– 2 points.
• Did one of you get the right answer?
– 1 point.
• Neither of you?
– For shame. 0 points.
– And eternal guilt.
Review Game Rules
• The List of Do Nots:
– Do not talk to each other, make noises, gesture,
give answers (my discretion here) between when
the question has been read and when I say,
“Compare answers.”
• Doing so will result in a disqualification for that round.
Don’t believe me? Try it.
– Do not fall asleep when I’m getting scores.
• If you’re not paying attention, I’m not giving you points.
Review Question 1
• A chunk of Substance X has a mass of 73 g and
occupies 75 cm3. Will it float in pure water?
– Yes it will float (density = 73/75 = 0.97 g/cm3).
Review Question 2
• How many significant figures are in the
number 6.02 x 1023?
– There are three (count right-to-left).
Review Question 3
• My dog weighs 19.1 kg. How much is this in
grams?
– 19,100 grams or 1.91 x 104 g.
Review Question 4
• A sloth can travel a maximum speed of 4
meters per minute. What is this speed in
miles per hour? [1 km = 0.621 mi]
– ≈0.1491 miles per hour.
Review Question 5
• Is soil an example of a compound, a
heterogeneous mixture, a homogeneous
mixture, or an element?
– Heterogeneous mixture.
Review Question 6
• Is blood an example of a compound, a
heterogeneous mixture, a homogeneous
mixture, or an element?
– Homogeneous mixture.
Review Question 7
• Is carbon an example of a compound, a
heterogeneous mixture, a homogeneous
mixture, or an element?
– Element.
Review Question 8
• Express 0.0029 in scientific notation.
– 2.9 x 10-3
Review Question 9
• Express 0.84 in scientific notation and with
three significant figures.
– 8.40 x 10-1
Review Question 10
• Which weighs more, a proton or an electron?
– Proton.
Review Question 11
• Where are electrons located?
– Around the nucleus moving at high speeds.
Review Question 12
• When the number of electrons in an atom
changes, what is created?
– Ion (or a positive/negative charge).
Review Question 13
• BONUS NON-CHEMISTRY QUESTION
• You may wager any/all of your points.
• Category: Not Chemistry
• Which was the first European country to settle
the island of Manhattan?
– Holland/The Netherlands (The Dutch)
Review Question 14
• There are three isotopes of Carbon – C-12, C13, and C-14. If the atomic mass of Carbon is
approximately 12.001 amu, which isotope is
most common?
– C-12.
Review Question 15
• How many grams are in 8.93 kilograms?
– 8930 grams.
Review Question 16
• Express the number 0.0089303 in scientific
notation.
– 8.9303 x 10-3
Review Question 17
Element
Atomic
Number
As
33
Mass
Number
Neutrons
5
98
150
O
Electrons
42
11
43
Protons
94
16
Complete the table. Note: All atoms are neutral.
Review Question 17
Element
Atomic
Number
Mass
Number
Protons
Neutrons
Electrons
As
33
75
33
42
33
B
5
11
5
6
5
Tc
43
98
43
55
43
Pu
94
244
94
150
94
O
8
16
8
8
8
Review Question 18
• What is the atomic number of an atom with
34 protons and 37 neutrons?
– 34 (also happens to be selenium).
Review Question 19
• How many milliliters in a deciliter?
– 100
Review Question 20
• How many neutrons does an F-20 atom have?
– 11
Review Question 21
• How many neutrons and protons does an F-20
atom have?
– 20
Review Question 22
• Copper has two main isotopes, Cu-63 and Cu65. Use copper’s mass on the periodic table –
which isotope is more abundant? AND How
can you tell?
– Cu-63, since Cu’s atomic mass is 63.55. That’s
closer to 63 than to 65.
Review Question 23
• Which weighs more, a neutron or an electron?
– Neutrons. Electrons weigh virtually nothing in
comparison.
Review Question 24
• Add the following numbers and express the
answer in significant figures:
• 256.1 g + 14.51 g + 506.123 g
– 776.7 grams.
Review Question 25
• What’s the difference between a mass
number and an atomic mass?
– Mass number = # of protons + # of neutrons.
– Atomic mass = weighted average of isotopes’
masses.
Review Question 26
• Ions differ in the number of which subatomic
particle?
– Electrons.
Review Question 27
• When salt dissolves into a beaker of water, is it
a chemical change or a physical change?
– Physical.
Review Question 28
• Isotopes differ in which subatomic particle?
Are their atomic numbers different? Mass
numbers?
– Neutrons.
– Atomic number never changes.
– Mass number (protons + neutrons) does change.
Review Question 29
• The total mass of three products in a chemical
change is 43.5 grams. What is the total mass
of the reactants, if there were only two?
– 43.5 grams – Law of Conservation of Mass.
Review Question 30
• 56 metal spheres each weighing 4 grams are
dumped into a large graduated cylinder. The
water rises from 29 mL to 41 mL. What is the
density of the spheres?
– 56*4 = Total Mass
– 41 mL – 29 mL = 12mL = Volume
– 224/12 = 18.667
Review Question 31
• During an experiment, a chemist finds the
density of aluminum to be 2.58 g/cm3. The
textbook, however, lists the density as 2.70
g/cm3. What is the percent error of the
chemist’s calculation?
– |(estimated – actual)| / (actual) x 100 = % error
– |(2.58 - 2.70) / (2.70)| x 100 = 4.44%
Review Question 32
• Is ice an element, compound, homogeneous
mixture, or heterogeneous mixture?
– Compound.
Review Question 33
• 6.1 x 4.32 = ??? in significant figures.
– 26