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Chemical Reactions

Total questions: 43

Worksheet time: 35mins

Name
Class
Date
1.

Which lab experiments below describe a situation where a chemical change has occurred? Check all that apply.

a)

After adding zinc (Zn) to hydrochloric acid (HCl), a student observes bubbles forming in the solution and a thermometer registers a 10°10\degree  change in temperature.

b)

A student uses a mortar and pestle (a grinding stone) to break up large pieces of ammonium thiocyanate ( NH4SCNNH_4SCN  ) into smaller pieces.

c)

After combining Unknown A (a solid, white crystal) with Unknown B (a clear, odorless liquid), there is a strong smell produced and a thermometer registers a  15°15\degree  change in temperature.

d)

A student dissolves sugar ( C6H6O6C_6H_6O_6  ) into water ( H2OH_2O  ). The sugar crystals seem to disappear.

2.

A scientist spilled a few drops of dilute hydrochloric acid (HCl) on a lab table. For safety purposes, the scientist sprinkled some baking soda ( NaHCO3NaHCO_3  ) onto the spill. Which observation would provide the best evidence that a chemical reaction occured?

a)

The baking soda and hydrochloric acid combined, and bubbles formed. 

b)

The baking soda absorbed the hydrochloric acid. 

c)

Some of the baking soda dissolved in the hydochloric acid.

d)

The hydrochloric acid evaporated, leaving only the baking soda. 

3.

What key words, when present in a question about chemical reactions, might indicate a chemical change is occuring? Check all that apply.

a)

Bubbling

b)

Fizzing

c)

Dissolving

d)

Evaporating

4.

A student combines two clear, colorless solutions shown here. When combined, the temperature changed from 25°25\degree  to  23°23\degree  and a white substance rapidly formed and settled at the bottom of the container. What most likely happened to produce these results?

a)

One of the original compounds came out of solution

b)

The solutions reacted chemically

c)

Some of the water froze into ice crystals

d)

Rapid evaporation of water occured, leaving a solid

5.

Carbon dioxide (  CO2CO_2  ) 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

6.

What evidence can you use to infer that a chemical reaction has occurred here?

a)

A dark solid formed on the zinc metal

b)

The zinc metal remained silver-colored and shiny

c)

The CuSO4CuSO_4 solution turned blue when the zinc metal was added

d)

None of these

7.

Observe the chemical equation shown here. What evidence of a chemical reaction is present when 2NO is added to  O2O_2  ?

a)

A gas is present

b)

The total number of atoms remains unchanged

c)

The state of matter remains the same

d)

A brown gas is produced

8.
How does a chemical change affect the composition of matter?
a)
Chemical change always changes the composition of matter.
b)
Chemical change always decreases the mass of the matter.
c)
Chemical change always increases the mass of the matter.
d)
Chemical change always changes the value of the matter.
9.
Which of the following is NOT a clue that a chemical change has taken place?
a)
transfer of energy
b)
change in color
c)
change of state
d)
production of a gas
10.
In a chemical change, how does the mass of the reactants compare to the mass of the products?
a)
The mass of the products is always greater than the mass of the reactants.
b)
The mass of the reactants is always greater than the mass of the products.
c)
The mass of the reactants is always equal to the mass of the products.
d)
It depends on the specific chemical change.
11.
Boiling water is an example of a _____.
a)
physical change
b)
chemical change
12.
Milk turning sour is a _____.
a)
physical change
b)
chemical change
13.
Dissolving salt in water is an example of a _____.
a)
physical change
b)
chemical change
14.
A metal rusting is an example of a _____.
a)
physical change
b)
chemical change
15.
Hydrogen and oxygen react to form water.  How much water would form if 4.8 grams of hydrogen reacts with 38.4 grams of oxygen?
a)
33.6 grams of water
b)
184.3 grams of water
c)
43.2 grams of water
d)
8.0 grams of water
16.

How many nitrogen atoms are there?

a)

4

b)

8

c)

10

d)

20

17.

How many phosphorus atoms are there?

a)

0

b)

1

c)

3

d)

4

18.

How many oxygen atoms are there?

a)

3

b)

6

c)

8

d)

16

19.

How many molecules of methane are there?

a)

0

b)

1

c)

2

d)

4

20.

How many atoms of carbon are there?

a)

0

b)

1

c)

2

d)

3

21.

How many atoms are there total?

a)

0

b)

1

c)

4

d)

6

22.

How many atoms of carbon are there?

a)

3

b)

6

c)

18

d)

24

23.

How many atoms of hydrogen are there?

a)

2

b)

4

c)

6

d)

11

24.

How many elements are there?

a)

0

b)

1

c)

3

d)

5

25.

How many different kinds of elements are there?

a)

4

b)

3

c)

2

d)

1

26.

How many molecules of caffeine are there?

a)

2

b)

5

c)

10

d)

24

27.

How many different kinds of elements are there?

a)

1

b)

3

c)

5

d)

8

28.

How many carbon atoms are there?

a)

2

b)

3

c)

8

d)

16

29.

How many atoms of carbon are there?

a)

2

b)

4

c)

12

30.

How many atoms of oxygen are there?

a)

4

b)

3

c)

2

d)

1

31.

How many molecules of fungicide are there?

a)

6

b)

4

c)

3

d)

1

32.

How many different kinds of elements are there?

a)

3

b)

4

c)

5

d)

6

33.

How many atoms of oxygen are there?

a)

0

b)

1

c)

2

d)

3

34.

How many total atoms are there?

a)

8

b)

5

c)

3

d)

1

35.
How many elements are in C6H12O6?
a)
1
b)
2
c)
3
d)
4
36.
Which of the following is a compound?
a)
Co
b)
O2
c)
C
d)
CO2
37.
Which is the correct formula for:
 three hydrogen (H)
one sulfur (S)
four oxygen (O)
a)
H3SO4
b)
HSO4
c)
H4S3O
d)
H2O
38.
The red numbers in the image below represent ________
a)
subscripts
b)
coefficients
c)
I don't know, and don't want to try
d)
None of the answers are correct
39.
The blue numbers in the image below represent ________
a)
I don't know, and don't want to try
b)
coefficients
c)
subscripts
d)
none of the answers are correct
40.
In this image, the symbols to the right of the arrow (in black) are called the_______.
a)
Products
b)
Reactants
c)
Subscripts
d)
Coefficients
41.
Na + MgF2 -->  NaF + Mg
What are the reactants?
a)
Na + MgF2
b)
Na
c)
NaF + Mg
d)
NaF
42.
NH3 ---> N2 + H2
What are the products?
a)
N2 + H2
b)
N2
c)
H2
d)
NH3
43.
All of the following are chemical changes except
a)
iron rusting
b)
water evaporating
c)
wood burning
d)
food rotting

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