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Worksheets8.5DE Chemical Formulas, Reactions, & Law of Conservation
Total questions: 40
Worksheet time: 35mins
Name
Class
Date
1.
How many atoms of hydrogen are in this molecule: 3(NH3)2Cr2O7?
a)
3
b)
6
c)
12
d)
18
2.
A chemical equation is a representation of a physical change.
a)
True
b)
False
3.
Which is NOT an example of chemical change?
a)
production of gas.
b)
change in color.
c)
change in size.
d)
transfer of energy.
4.
A copper penny turning greenish after a few years is an example of...
a)
Chemical Change
b)
Physical Change
5.
Which of the following is a PHYSICAL change?
a)
Getting a haircut
b)
Rusty metal
c)
sour milk
d)
A compound
6.
Which of the following is a sign that a chemical reaction has occurred?
a)
change in shape
b)
melting
c)
formation of a gas
d)
dissolving
7.
Is burning wood a chemical or physical change?
a)
chemical
b)
physical
8.
A change in the size, shape, or state of matter.
a)
chemical change
b)
physical change
c)
chemical reaction
d)
electron change
9.
Four students performed four different investigations by combining different substances. Their results are shown in the table provided. In which experiment are new substances being formed?
a)
Experiment 1
b)
Experiment 2
c)
Experiment 3
d)
Experiment 4
10.
A clear liquid from a flask is poured into another clear liquid in a beaker. Which of the following results of this procedure would indicate a new substance was formed?
a)
The level of the substance in the beaker is higher after the other liquid is added.
b)
A yellow solid forms and then settles to the bottom of the beaker.
c)
Small white crystals are left behind in the flask that held the first liquid.
11.
Which of the following is an example that includes evidence of a chemical reaction?
a)
A sample of zinc is placed in water and it settles to the bottom
b)
A solid block of ice is heated and it completely melts into a liquid.
c)
Sugar that is burned gives off an odor and turns brown and then black.
d)
A tomato is placed into a blender and chopped up into smaller pieces.
12.
Evidence of a chemical reactions is anything that shows -
a)
a new substance has formed
b)
a solid dissolved in a liquid
c)
interaction between 2 gases
d)
a change in the state of matter
13.
If you break a piece of glass, the shape of the glass changes, but the properties in the fragments remain the same. Which of the following has occurred?
a)
A chemical change.
b)
A temperature change.
c)
A phase change.
d)
A physical change.
14.
Students react baking soda & vinegar.
Which of the following would provide the evidence that the number of atoms present before a chemical reaction is equal to the number of atoms present after the chemical reaction?
Which of the following would provide the evidence that the number of atoms present before a chemical reaction is equal to the number of atoms present after the chemical reaction?
a)
The mass of the plastic bag, baking soda, and vinegar before the reaction was equal to the mass after the reaction.
b)
Bubbles were produced during the reaction, which meant that a gas was being produced.
c)
The plastic bag did not change in any way, indicating that it was not involved in the reaction.
d)
The mass of the baking soda was exactly equal to the mass of the vinegar used to create the chemical reaction.
15.
Which of the following is true of the law of conservation of mass?
a)
The same number and type of each atom will always be present before and after a chemical reaction takes place.
b)
Some of the atoms present before the reaction will always be lost during a chemical reaction.
c)
Some of the atoms will always be changed into a different type of atom by a chemical reaction.
d)
During a chemical reaction, atoms will always be combined into much larger molecules.
16.
Which of the following is the best description of the results of a chemical reaction?
a)
The substance seems to disappear after dissolving in water.
b)
The substance changes from liquid to solid at a low temperature.
c)
The reaction can be reversed to get back the original substance.
d)
A new substance with different properties is formed.
17.
Which of the following is a chemical change?
a)
Baking soda and vinegar producing gas bubbles
b)
A chocolate bar melting
c)
Powdered lemonade dissolving in water
d)
Frosting a cake
18.
The substances listed to the left of the arrow in a chemical reaction are called the _______________.
a)
products
b)
reactants
c)
substances
d)
materials
19.
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
20.
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?
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.
21.
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
22.
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
23.
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
24.
Does this chemical equation follow the Law of Conservation of Mass?
a)
Yes
b)
No
c)
I don't know
d)
Maybe
25.
Does this chemical equation follow the Law of Conservation of Mass?
a)
Yes
b)
Maybe
c)
No
26.
Examine the following chemical reaction:
H20 + CO2 → C6H12O6 + O2
What are the reactants?
a)
H20 + CO2
b)
C6H12O6 + O2
c)
→
d)
H20 + CO2→ C6H12O6 + O2
27.
Examine the following chemical reaction:
H2O2 → H2O + O2
What are the products
a)
H2O2
b)
H2O + O2
c)
H2O2→H2O + O2
28.
Which of the following reactions is balanced?
a)
2CH4 + O2 -> CO2 + H2O
b)
CH4 + 2O2 -> CO2 + H2O
c)
CH4 + 2O2 -> CO2 + 2H2O
d)
None of the chemical equations are balanced.
29.
Which of the following chemical equations is balanced?
a)
2HClO -> 2H₂O + 2Cl₂O
b)
CuO + 2HCl -> 2CuCl₂ + H₂O
c)
MgCl₂ + NaF -> MgF₂ + NaCl
d)
2C₂H₂ + 5O₂ -> 4CO₂ + 2H₂O
30.
Which of the following describes a precipitate?
a)
a liquid forms when a block of metal is heated
b)
a solid forms when one liquid is poured into another
c)
a gas forms when a solid is placed in a liquid
d)
bubbles form when an acid is poured on a rock
31.
The Law of Conservation of Mass states that -
a)
the number and type of atoms on both sides of a chemical reaction are equal
b)
there are more atoms on the reactant side than the product side
c)
there are more atoms on the product side than the reactant side
d)
the mass of the product will not equal the reactants
32.
In the equation,
2Mg + O2 ---> 2MgO, which are the reactants?
a)
2Mg + O2
b)
2MgO
c)
2Mg and MgO
d)
O2 and MgO
33.
What is the right part of a chemical equation called?
H2 + O → H2O
H2 + O → H2O
a)
Reactants
b)
Products
c)
Yields
d)
Chemical Equation
34.
How many atoms of carbon (C) are in C6H12O6?
a)
3
b)
6
c)
12
d)
24
35.
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
36.
KMnO4
How many total atoms are in this compound?
How many total atoms are in this compound?
a)
1
b)
3
c)
6
d)
8
37.
If reaction starts with 20g of reactants it should produce
a)
a total of 40g of products
b)
a total of 10g of products
c)
a total of 80 g of products
d)
a total of 20g of products
38.
How many atoms of Oxygen are in Al₂(SO₄)₃?
a)
4
b)
12
c)
7
d)
24
39.
How many Calcium atoms are in this compound?
Ca (OH)2
Ca (OH)2
a)
2
b)
3
c)
1
d)
4
40.
Subscripts tell us the number of _________ of an element and coefficients tell us the number of __________ of a substance.
a)
molecules ; atoms
b)
reactants ; products
c)
atoms ; molecules
d)
products ; reactants
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