Possible STEM Chemistry Challenges
Which of the following elements are metals:
P
S
Na
Cu
Sn
I
W
Answer Key Which of the following elements are metals:
P
S
Na
Cu
Sn
I
W
Align atoms, based on their atomic size, from smallest to largest:
Cs
K
Ca
H
He
Li
C
Answer Key Align atoms, based on their atomic size, from smallest to largest:
He
H
Li
C
Ca
K
Cs
Which of the following elements exist as gases at normal conditions (0 oC, 1 atm)
Na
O
Au
Cl
Ar
I
N
Answer Key Which of the following elements exist as gases at normal conditions (0
oC, 1 atm)
Na
O
Au
Cl
Ar
I
N
Place elements in order of their discovery year, from ancient times to most recent:
Tc
O
Na
Ds
Ne
Fe
Al
Answer Key Place elements in order of their discovery year, from ancient times to
most recent:
Fe
O
Na
Al
Ne
Tc
Ds
Which 6 elements compose most of the human body (by mass):
Answer Key Which 6 elements compose most of the human body (by mass):
O (65%)
C (18.5%)
H (9.5%)
N (3.2%)
Ca (1.5%)
P (1.0%)
Which 6 elements compose most of the Earth crust (by mass):
Answer Key Which 5 elements compose most of the Earth crust (by mass):
O
Si
Al
Fe
Ca
Which 7 non-radioactive elements are diatomic at normal conditions (0 oC, 1 atm)
Answer Key Which 7 non-radioactive elements are diatomic at normal conditions
(0 oC, 1 atm)
H
N
O
F
Cl
Br
I
Which of the elements don’t exist (without looking at a periodic table)
Hf
Fu
Ba
Uh
Cd
Tx
Oh
Answer Key Which of the elements don’t exist (without looking at a periodic table)
Hf
Fu
Ba
Uh
Cd
Tx
Oh
Element Names
Match an element with the meaning of its name
Acid-forming
Am
Moon
Ar
Violet
Ca
America
Cl
Lime
He
Stone
I
Bringer of Light
Li
Idle
O
Sun
Po
Poland
P
Earth
Se
Greenish-Yellow
Te
Answer Key Match an element with the meaning of its name
Acid-forming
O
Moon
Se
Violet
I
America
Am
Lime
Ca
Stone
Li
Bringer of Light
P
Idle
Ar
Sun
He
Poland
Po
Earth
Te
Greenish-Yellow
Cl
Juggling the Gas Law
Using PV = nRT (ideal gas law) and other fundamental equations, derive equation
for density of gas (depends on pressure, temperature, and molecular weight).
Answer Key Using PV = nRT (ideal gas law) and other fundamental equations,
derive equation for density of gas (depends on pressure, temperature, and
molecular weight).
d = (PMw)/(RT)
Making Up Elements
Write up all possible elements using letters in the word CHEMISTRY (letters can be
reused).
Answer Key Write up all possible elements using letters in the word CHEMISTRY
(letters can be reused).
C, H, He, I, S, Y, Er, Ce, Ir, and many more…
Salt formulas. Rules of “the game”:
• Total positive charge must cancel total negative charge in salts
• Common charges (more commonly referred to as oxidation states) are listed here.
Compose a stable derivative between:
a) Ca and Br
b) H and S
c) Si and O (Si is +4)
d) Al and O
e) Na, one C, O
f) Ba, O, H
g) Ca, one Si, O
Answer Key: CaBr2, H2S, SiO2, Al2O3, Na2CO3, Ba(OH)2, CaSiO3.
Separating Mixtures Puzzle
How would you separate a mixture of:
a) sand, table salt
b) sand, table salt, iron fillings, vegetable oil
c) sand, table salt, iron fillings, ZnO, vegetable oil, gasoline
Answer Key:
a) sand, table salt. Add water (salt will dissolve), filter sand, evaporate
water, salt will be left over.
b) sand, table salt, iron fillings, vegetable oil. Use magnet to get iron out. Add
water (salt will dissolve), collect oil (will float on top), filter sand,
evaporate water, salt will be left over.
c) sand, table salt, iron fillings, ZnO, vegetable oil, gasoline. Use magnet to get
iron out. Add water (salt will dissolve), filter sand and ZnO through a
filter paper. Using a separatory funnel, separate water (with salt) from
oil (dissolved in gasoline). Distill gasoline – oil will remain. Evaporate
water – salt will remain. Add HCl to the mixture of sand and ZnO – ZnO
will dissolve, sand can be filtered then.
Draw a sketch of an apparatus
(design your own if you’ve never seen one before) that:
a) Can filter precipitate from a solution
b) Can separate two liquids that boil at two different temperatures
c) Can separate three liquids that boil at three different temperatures
d) Can separate two liquids that do not mix with one another
e) Can heat a liquid in a flask at its boiling point. Points to consider: the flask
cannot be left open (because the liquid will boil away) and the flask cannot
be capped (pressure created by the vapor will have the flask explode).
Answer Key (consult with Dr. D ahead of time if solutions are not clear):
a) Can filter precipitate from a solution. (use filtering funnel and flask)
b) Can separate two liquids that boil at two different temperatures (use
distillation apparatus)
c) Can separate three liquids that boil at three different temperatures (use
distillation apparatus with a distillation spider)
d) Can separate two liquids that do not mix with one another (use separatory
funnel)
e) Can heat a liquid in a flask at its boiling point. Points to consider: the flask
cannot be left open (because the liquid will boil away) and the flask cannot
be capped (pressure created by the vapor will have the flask explode). (use
reflux apparatus)
Matching Puzzles
Match a formula with its name (level 1)
CaCO3, Cu2SO4, CuS, CuSO3, CuSO4, Fe(NO2)3, Fe(NO3)2, H2S, HCl, HClO4, HCN, NH3,
SO2, SO3
Answer key is shown. Before showing to team, delete the second column.
Dihydrogen sulfide
H 2S
Sulfur dioxide
SO2
Sulfur trioxide
SO3
Hydrogen chloride
HCl
Hydrogen cyanide
Perchloric acid
Ammonia
Iron(II) nitrate
Iron(III) nitrite
Limestone
Copper(II) sulfite
Cupric sulfate
Cuprous sulfate
Copper(II) sulfide
HCN
HClO4
NH3
Fe(NO3)2
Fe(NO2)3
CaCO3
CuSO3
CuSO4
Cu2SO4
CuS
Match a formula with its description/application (level 2)
C20H42, CaCO3, CaSO4•2H2O, H2S, H2SO4, He, HF, Hg, Mg(OH)2, N2, N2O, NaOH, O3, SiO2
Answer key is shown. Before showing to team, delete the second column.
Component of air
N2
Laughing gas
N2O
Sulfuric acid
H2SO4
Smell of rotten eggs
H 2S
Only liquid metal at room temperature
Hg
Air is enriched in this gas after lightning O3
Acid that dissolves glass
HF
Lye
NaOH
Milk of magnesia
Mg(OH)2
Element identified in the sun but only
He
later found on Earth
Chalk
CaCO3
Crayons
C20H42
Sand
SiO2
Gypsum
CaSO4•2H2O
Match a formula with its description/application (level 3)
As, CH4, Cl2, Fe2O3•H2O, H2SO4, HCl, Hg, Mg(OH)2, MgSO4, NaF, NaHCO3, NaI, P4S3, UF6
Answer key is shown. Before showing to team, delete the second column.
Used in tooth fillings
Hg
Is contained in car batteries
H2SO4
Our stomach has this acid
HCl
Common additive in a table salt
NaI
Epsom Salt
MgSO4
Matches have this
P4S3
Poison that might have killed Napoleon
As
Common ingredient of antacids
Mg(OH)2
Used during preparation of a nuclear
UF6
bomb
Commonly used in toothpaste, to
NaF
prevent cavities
Chemical Weapon during WWI
Used quite a bit in baking
Natural gas
Rust
Cl2
NaHCO3
CH4
Fe2O3•H2O
Fill an empty Periodic Table.
Look at a periodic table for 90 sec. Fill an empty periodic table. Each incorrect
answer cancels out a correct answer. (Empty Periodic Table provided)
Find 9 first elements.
Look the file attached.
Periodic Table of mistakes.
Look the file attached.
Balancing equations using M&Ms.
Description (great find, Joel!): R – red, B – blue, G – green. R2B means two reds and
one blue and cannot be broken down when balancing. The goal is to make number
of M&Ms on both sides of the reaction to match one another.
Easy: R2 + B2 = R2B (Answer Key: 2R2 + B2 = 2R2B)
Intermediate: R2B + G = GBR + R2 (Answer Key: 2R2B + 2G = 2GBR + R2)
Difficult: RG4 + B2 = RB2 + G2B (Answer Key: RG4 + 2B2 = RB2 + 2G2B)
Be in Mendeleev’s Shoes (See a related pdf file, from Flinn Scientific, actually).
1) Print copies. Cut all the 9 cards and take one card (any one) away. Remember
order before cutting the cards, this is your answer key.
2) Students’ goal is to put together a table 3x3, identify a missing element, and
predict its properties (should be an average of nearby elements).
3) Info to help: each element has molecular weight (top left), oxidation states
(top right), density (below molecular weight), boiling and melting point
(further down).
Drawing Lewis Structures – Puzzle.
Description: In order for molecules to be stable, elements that compose them need
to have a certain number of bonds (lines) surrounding them.
Group # 1
2
3
4
5
6
7
# of
1
2
3
4
3
2
1
bonds
Element can have a single, double, or triple connection to a different element.
Draw stable structures:
Easy: N2, CO2, H2O2, C2H2, N2H4
Medium: Na2CO3, K3PO4 (here, P has 5 bonds), H2SO4 (here, S has 6 bonds). In all of
these examples, Na, K, and H are connected to O atoms.
Hard: C4H2, P4, C4O4, B3N3
Answer Key: ask Dr. D if needed.
Isomers Puzzle
- Isomers are made from same atoms but arranged differently
- For example, isomers of C4H10 (feel free to build a model using the provided kit):
- note how it's possible to rotate around single bonds
- note that all other possibilities will be duplicates of the two structures above
Assignment: Predict all isomers of:
C5H12 (3 isomers)
C4H8 (6 isomers)
C4H6 (9 isomers)
Answer key (only carbon-carbon bonds are shown):