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Chemistry Challenge Problems

Total questions: 100

Worksheet time: 3hrs 20mins

Name
Class
Date
1.
Which letter represents a proton?
a)
A
b)
B
c)
C
d)
D
2.
All of the mass of an atom comes from what location?
a)
nucleus
b)
electron cloud
3.
Which subatomic particle has a neutral or no charge?
a)
Proton
b)
Electron
c)
Neutron
4.
Which of the following is an element?
a)
FeO
b)
O2
c)
NaOH
d)
SiO2
5.
Which of the following is a compound?
a)
Ca
b)
Pb
c)
H2
d)
MgBr
6.
How many elements are in the compound C2H8O ?
a)
2
b)
1
c)
3
d)
0
7.
How many total atoms are in the compound H2SO4?
a)
6
b)
5
c)
7
d)
3
8.

Which one of the following compounds is has five (5) total atoms?

a)

H2O

b)

CaCu3

c)

C6H12O6

d)

H2Cl3

9.
How many Sodium atoms are in the compound 6NaCl?
a)
1
b)
12
c)
6
d)
4
10.
How many Carbon atoms are on the product side of this chemical equation?            
2C2H2 + 5O2  --->  4CO2 + 2H2O
a)
2
b)
3
c)
4
d)
5
11.
How many Hydrogen atoms are on the reactant side of this chemical equation?            
2C2H2 + 5O2  --->  4CO2 + 2H2O
a)
2
b)
4
c)
6
d)
8
12.
Does this chemical equation follow the Law of Conservation of Mass? (Hint: Is it balanced?)       
2C2H2  +  5O2 ---> 4CO2  +  2H2O 
a)
No
b)
Yes
c)
maybe
d)
huh?
13.
According to the Law of Conservation of Mass, –
a)
matter is not created or destroyed in a chemical reaction.
b)
matter is always created in a chemical reaction.
c)
matter is always destroyed in a chemical reaction.
d)
matter is created and then destroyed in a chemical reaction.
14.
Which of the following is an example of a chemical reaction?
a)
A marshmallow turning black when heated over a fire
b)
A powder dissolving in water to make lemonade
c)
An ice cube melting into a puddle of water
d)
Salt crystals being crushed into a powder
15.
What happens when chemical bonds break and new bonds form?
a)
a physical change
b)
a chemical reaction
c)
matter is destroyed
d)
surface area increases
16.
The principle of conservation of mass is true
a)
only for reactions that take place in open systems.
b)
only for reactions that take place in closed systems.
c)
for reactions in both open and closed systems.
d)
for no reactions at all.
17.
When heated, oxygen reacts with copper to form copper oxide:
If this reaction occurs in a sealed container, will the mass of the container and everything in it increase, decrease, or stay the same and why?
a)
The mass will stay the same because the number of each kind of atom stays the same.
b)
The mass will increase because a new kind of molecule is formed.
c)
The mass will decrease because two substances combine to form one substance.
d)
More information is needed to tell if the mass will change.
18.
What is the Law of Conservation of mass?
a)
Mass is created in a chemical reaction
b)
Mass is created in a physical change
c)
New chemicals formed from a chemical reaction have a larger overall mass than the original reactants
d)
Mass is never created or destroyed
19.
In a reaction A + B ----> C,  reactant A has 5g and product  C has 9g. How many grams should reactant B have? 
a)
4g
b)
5g
c)
9g
d)
14g
20.
A chemical reaction is balanced when
a)
both sides have the same elements
b)
Both sides have the same  number of atoms
c)
Same subscripts
d)
Same coefficients
21.
Matter can not be created nor destroyed: it can only be
a)
Destroyed a little bit
b)
Invisible
c)
Transformed, changed
d)
None of the above
22.
Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?
a)
The shape of the coal changes
b)
Oxygen is present
c)
A new substance is produced
d)
Coal is made up of more than one element
23.
You know you a chemical reaction has occurred if 
a)
there is a precipitate.
b)
there is a color change.
c)
there is a temperature change.
d)
All of these answers are evidence.
24.
Which of the following is evidence of a chemical reaction?
a)
fizzing
b)
water changing to ice
c)
saltwater
d)
paper being cut in half
25.
The Law of Conservation of Mass states
a)
that matter exists in all states and reacts the same
b)
that matter can only be changed into new substances by introducing a catalyst
c)
that matter exists in the same state throughout any chemical change
d)
that matter cannot be created or destroyed and that the mass of the products must equal the mass of the reactants
26.
Which is an example of a chemical reaction?
a)
paper cut into small pieces
b)
chocolate melting in a pan
c)
flour and sugar mixed in a bowl
d)
cookies baking in an oven
27.
At the end of chemical reactions, what is the total mass of the reactants compared to the total mass of the products?
a)
the product is doubled
b)
the product is half the mass of the reactants
c)
the mass is the same
d)
the mass changes depending on the reaction
28.
Does this chemical equation follow the Law of Conservation of Mass?
a)
Yes
b)
No
c)
I don't know
d)
Maybe
29.
Which of the following is an example of a chemical change?
a)
rusting of a bicycle
b)
painting a house
c)
washing a dog
d)
tearing up a newspaper
30.
Which is an example of a physical change?
a)
sodium and chlorine form salt
b)
a copper ring turns white and green
c)
a log burns in a fire
d)
using sand and water to build a sand castle on a beach
31.
You combine 2g of vinegar and 4 g of baking soda in a zip lock bag.  The weight of all contents and the bag before the reaction is 7.2 g.  What should it weigh after the reaction?
a)
6 g
b)
Somewhere between 6 & 7.2 g
c)
Less than 6 g
d)
7.2 g
32.
A chemical reaction between Hydrogen and Oxygen produces water. If 2g of Hydrogen and 4g of Oxygen react together, how much water is produced?
a)
2g
b)
4g
c)
6g
d)
Not enough information to answer
33.
The total amount of matter (atoms) before and after a chemical reaction (change), remains the same.
a)
True
b)
False
34.

A student is shown a picture of the atom to the side. What element, based on the subatomic particles in the atom, is shown?

a)

Beryllium

b)

Lithium

c)

Helium

d)

Oxygen

35.

 

What element contains 7 protons and 5 valence electrons?

a)

Boron

b)

Vanadium

c)

Nitrogen

d)

Lithium

36.

The atomic number of an element is equal to its number of protons. Therefore, a logical conclusion is that the number of protons determines an element’s-

a)

Mass and atomic weight.

b)

The number of stable isotopes.

c)

Identity

d)

State of matter

37.

Compare the data shown in the table. What reasonable conclusion can be made from the information given?

a)

Element 1 has the same atomic mass as Element 4

b)

Element 3 has a very similar chemical properties as Element 4

c)

Element 1 has very similar chemical properties as Element 3

d)

None of the above

38.

Four students were asked to name the parts of an atom that determine the atom’s identity and chemical properties. The students’ responses are shown in the table below.

Which student’s responses are correct?

a)

Student 1

b)

Student 2

c)

Student 3

d)

Student 4

39.

A Student drew atomic models of four atomic models. Based on the drawings, which one is the least reactive?

a)

Chlorine, because it has three energy levels with seven electrons in the third level

b)

Gallium, because it has four energy levels with three electrons in the fourth level

c)

Neon, because it has two energy levels with eight electrons in the second level

d)

Tin, because it has five energy levels with four electrons in the fifth level

40.

An atom of which element is represented by this model?

a)

Carbon (C)

b)

Neon (Ne)

c)

Sodium (Na)

d)

Boron (B)

41.

A student is studying calcium, a highly reactive element that humans need for strong bones. Which characteristic of calcium is most closely related to its chemical reactivity?

a)

The 20 protons in each atom of calcium

b)

The 2 valence electrons in each atom of calcium

c)

The atomic mass of calcium, which is 40.078 amu

d)

The density of calcium, which is 1.54 g/cm3

42.

Valence electrons are electrons in the shell

a)

furthest from the nucleus

b)

closest to the nucleus

c)

having the lowest energy level

d)

that has the fastest electrons

43.

All atoms are most stable with (or would "prefer") how many electrons in their valence shell?

a)

1

b)

2

c)

8

d)

18

44.
Number of C's in 2Na₂CO₃
a)
1
b)
2
c)
3
d)
5
45.
How many Elements are in the compound C2H8O ?
a)
2
b)
1
c)
3
d)
0
46.
How many total atoms are in the compound C2H8O ?
a)
11
b)
2
c)
8
d)
1
47.
How many Sodium (Na) are in 6NaCl?
a)
1
b)
12
c)
6
48.
How many Chlorine are in MgCl2?
a)
2
b)
1
c)
3
49.
How many Magnesium are in 10MgCl2?
a)
10
b)
5
c)
20
50.
How many elements are in C6H12O6?
a)
1
b)
2
c)
3
d)
4
51.
Number of H in 3(NH₄)₂CrO₄
a)
4
b)
2
c)
8
d)
24
52.
How many atoms are there TOTAL in:
H2SO4
a)
6
b)
5
c)
7
d)
3
53.
Number of N in (NH₄)₂CrO₄
a)
1
b)
2
c)
8
d)
16
54.
Which of the following is an example of a compound?
a)
a.  Sodium (Na)
b)
a.  Oxygen (O2)
c)
a.  Chlorine (Cl)
d)
a.  Water (H2O)
55.

Each vertical column on the periodic table is called a...

a)

group

b)

tower

c)

period

d)

crew

56.

What is the chemical symbol for Lead?

a)

Le

b)

Fe

c)

Ld

d)

Pb

57.

These elements located on the "stair-step" line are sometimes called "semiconductors."

a)

Metals

b)

Nonmetals

c)

Metalloids

d)

Groups

58.

Ryan takes three small ice cubes and places them in a glass plate. He leaves them for an hour at the room temperature. Which of these would NOT change in the water after one hour?

a)

temperature

b)

mass

c)

shape

d)

physical state

59.

Sam wants to demonstrate how water changes from a solid to a gas. He places ice in a pot on a stove. What variable is causing water to change state?

a)

the container the ice is placed in

b)

the temperature of the air surrounding the ice

c)

the heat from the stove

d)

the time that has lapsed since the ice was removed from the freezer

60.

A solution is a mixture that looks exactly the same everywhere. These mixtures cannot be separated by a filter. Which of these could use a filter to separate the mixture?

a)

a mixture of rocks and soil

b)

a mixture of salt and water

c)

a mixture of sugar and water

d)

a mixture of juice and water

61.

Which of these actions cause a PHYSICAL change?

a)

rusting of metal pipes

b)

burning a log

c)

cooking an egg

d)

crushing an aluminum can

62.

Rusting metal is an example of a ____ change.

a)

chemical

b)

phase

c)

state

d)

physical

63.

Salt water, a mixture, is made by dissolving salt in water. Mixtures like this can be separated by using the physical properties of the mixture. Which would be the best way to separate a mixture made of salt and water?

a)

evaporation

b)

chromotography

c)

magnetism

d)

filtering

64.

Josh decided to mix some vinegar with baking soda. He knew that a reaction occurred because he made careful observations. He noted that the mixture started to foam up and bubble, and it was white in color. How did Josh know that a chemical reaction occurred?

He was sure a reaction occurred because of

a)

the color of the mixture

b)

the smell of the vinegar

c)

the volume of the mixture

d)

the formation of a gas

65.

Which is an example of a chemical change?

a)

baking a cake

b)

ripping paper

c)

stretching a rubber band

d)

chopping wood

66.

Water is one of the most important things to you and to all living things. The fact that you can measure the volume of room temperature water with a beaker is a clue that room temperature water is in liquid form.

If you keep lowering the temperature of the water, it will eventually harden, taking on a definite shape. This means that the water has changed form, into a ___.

a)

plasma

b)

brick

c)

solid

d)

gas

67.

What physical property would you use to separate these jelly beans?

a)

length

b)

mass

c)

color

d)

texture

68.

Car windows fog up in cold weather because water vapor condenses on the inside surface of the glass. Condensation occurs when the dew point of the air inside the car is warmer and more humid than the air outside the car window. When warm water vapor touches the cooler glass, the vapor cools down and becomes water.

Which might be the main source of the warm water vapor in a car?

a)

leather seats

b)

ice cold drinks

c)

people breathing

d)

car electronics

69.

Frank found a pile of wood near a campsite, and he believed it had been chemically changed. What property did Frank most likely observe to believe this?

a)

the surface of the wood felt wet

b)

the color of the wood was black

c)

the wood had been chewed

d)

the wood had been chopped

70.

Use the basic properties of solids, liquids, and gases to identify the correct state of matter in the image.

a)

(A) gas, (B) liquid, (C) solid

b)

(A) solid, (B) liquid, (C) gas

c)

(A) liquid, (B) solid, (C) gas

d)

(A) solid, (B) gas, (C) liquid

71.

Casey is given a sample mixture. Which component could be separated with a magnet?

a)

calcium carbonate

b)

glucose

c)

iron filings

d)

silica sand

72.

Mary collected some pond water to analyze in the science lab. She noticed that the water container had some sand at the bottom and bits of wood floating on top. How can Mary easily separate the sand from the water?

a)

filter out the sand

b)

pick out the sand

c)

evaporate the water

d)

shake the water and pour off the sand

73.

Franklin stores a gallon of milk in the refrigerator. Three weeks later, he notices that the milk has frozen on the top layer and also smells strongly of a sour odor. Which statement justifies that a physical change has occurred in the milk?

a)

There is less milk since some of it froze.

b)

There is a bacterial culture growing in the milk causing the sour smell.

c)

The frozen layer on top of the milk can melt into liquid when left at room temperature.

d)

Some of the milk sugar has been lost, leading to a more sour smell and taste

74.

A small bottle of water is left on the shore of a very large lake on an extremely cold winter night. What is MOST LIKELY to be observed the next morning?

a)

Neither the bottle of water or the lake have become solid.

b)

The bottle of water has become solid but the lake has not.

c)

The lake has become solid but the bottle of water has not.

d)

Both the lake and the bottle of water have become solid.

75.

Choose all three examples of a chemical change.

a)

ice melts in the hot sun

b)

a dead rabbit decomposes

c)

a tree is burned in the forest

d)

a block of cheese is cut in half

e)

the top of a metal fence rusts

76.

Matter can change: the changes can be physical or chemical. When a physical change happens, nothing new is formed. During a physical change, matter changes form; it can be crushed or torn or change state. When a chemical change occurs, something new is formed. The reactant or reactants change and become something new. For example, a piece of iron can rust. The rust is the new substance that is formed. It is called iron oxide. How can you tell if a chemical change has taken place? There are certain observations you can make:1. temperature change2. color change3. gas or bubbles produced4. an odor is created5. combining two liquids forms a solid called a precipitate.

Ms. Brown asked her students to combine some regular cow's milk with white vinegar. Each group mixed 1 cup of warm milk with 4 tablespoons of vinegar in a glass measuring cup. After stirring the mixture, the students poured the liquids through a strainer into another beaker. The picture above shows the results of mixing warm milk with vinegar. What type of change is this? Explain.

a)

It is a chemical change because two liquids mixed together something new and different.

b)

It is a physical change because it is a mixture of two liquids.

c)

It is a chemical change because there was a change in temperature of the milk.

d)

It is a physical change because you can separate the parts with a strainer.

77.

Claudia was assigned the task of making a model volcano. To make her volcano erupt, Claudia mixed baking soda and vinegar. When these two substances came in contact with one another they produced bubbles and fizzed making it look like the volcano was erupting. After "erupting" her volcano Claudia's teacher told her that she had created a chemical reaction inside of the volcano. What evidence did Claudia see of a chemical reaction?

a)

change in odor

b)

gas production

c)

change in color

d)

light production

78.
In this image, the information in red is called the_______.
a)
Products
b)
Reactants
c)
Chemical Subscript
d)
Ingredients
79.
In this image, the information to the right of the arrow (in black) is called the_______.
a)
Product
b)
Reactant
c)
Chemical Subscript
d)
Final chemical
80.
What does the Law of Conservation of Mass state?
a)
Matter cannot be gained or lost in a chemical reaction.
b)
Matter can only be lost in a chemical reaction.
c)
Matter can only be gained in a chemical reaction.
d)
Matter can be gained and lost in a chemical reaction. 
81.
How many ELEMENTS are in the compound H2O
a)
1
b)
2
c)
3
d)
4
82.
How many ELEMENTS are in the compound O2
a)
1
b)
2
c)
3
d)
4
83.
Is the following equation balanced or unbalanced ? 
Al + O2 --> Al2O3
a)
Balanced
b)
Unbalanced
84.
Is the following equation balanced or unbalanced ? 
N2 +3 H2 --> 2NH3
a)
Balanced
b)
Unbalanced
85.
How many TOTAL atoms are in 2CaO2
a)
2
b)
3
c)
5
d)
6
86.

Identify the reactants in the following equation.

3HFe2O →H+2FeH+O

a)

H+2FeH+O

b)

3HFe2O

87.

Identify the products in the following equation.

3HFe2O →H+2FEH+O

a)

H+2FEH+O

b)

3HFe2O

88.

Identify if the following equation is unbalanced or balanced.

4K+P3→3KP+K

a)

Unbalanced

b)

Balanced

89.

Identify if the following equation is unbalanced or balanced.

O3+2C→3OC

a)

Unbalanced

b)

Balanced

90.

Identify if the following equation is unbalanced or balanced.

2(N)2→4N

a)

Unbalanced

b)

Balanced

91.

Identify if the following equation is unbalanced or balanced.

5C4O8→10C+2C5O20

a)

Unbalanced

b)

Balanced

92.

Identify if the following equation is unbalanced or balanced.

HeC4O8→C4+2HeO

a)

Unbalanced

b)

Balanced

93.

Is this balanced?...

Al + O2 --> 2Al2O3

a)

Yes!

b)

No!

94.
Why is the following chemical equation not balanced?
H2 + O2 --> H2O
a)
each side of the equation has a different number of oxygen atoms
b)
each side of the equation has a different number of hydrogen atoms
c)
each side has the same mass
95.

CuO+H2O → Cu(OH)2CuO+H_2O\ \rightarrow\ Cu\left(OH\right)_2  

Is the  equation balanced or unbalanced?

a)

balanced

b)

unbalanced

96.

What coefficient should be used to make the following equation balanced?

N2 + O2 --> ___NO

a)

1

b)

2

c)

3

d)

4

97.

The small numbers in a chemical formula:

(the BLUE numbers)

a)

Subscripts

b)

Coefficients

c)

Numbers

d)

Molecules

98.
Is this equation balanced?
a)
yes
b)
no
c)
Not enough information
99.
What is the product ?
N2 + 3 H2 ------>   2 NH3
a)
N2
b)
3 H2
c)
N2 + 3 H2
d)
2 NH3
100.
Atoms of the same element that differ in the number of neutrons.
a)
Ion
b)
Isotope
c)
Element 
d)
Atom

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