WorksheetsLaw of Conservation of Mass
Total questions: 25
Worksheet time: 16mins
Name
Class
Date
1.
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
2.
In a reaction A + B ----> C, reactant A has 5g and product C has 9g. How many grams does reactant B should have?
a)
4g
b)
5g
c)
9g
d)
14g
3.
In a reaction A + B ----> C, reactant A has 5g and product C has 9g. How many grams does reactant B should have?
a)
4g
b)
5g
c)
9g
d)
14g
4.
The number in front of a compound or element is a
a)
Subscript
b)
Coefficient
c)
Superscript
d)
Charge
5.
The number to the lower side of an element is a
a)
Subscript
b)
Superscript
c)
Coefficient
d)
Charge
6.
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
7.
Which is Chemical Equation is Balanced?
a)
CH₄+O₂------CO₂+2H₂O
b)
H₂+O₂-----2H₂O₄
c)
4Al+3O₂-----2Al₂O₃
8.
How many nitrogen atoms does NH3 have?
a)
1
b)
2
c)
3
d)
4
9.
Is this equation balanced or unbalanced?
2Fe2O3 + 3C --> 4Fe + 3 CO2
2Fe2O3 + 3C --> 4Fe + 3 CO2
a)
balanced
b)
unbalanced
10.
How many oxygen atoms are in this chemical formula?
a)
6 oxygen atoms
b)
2 oxygen atoms
c)
3 oxygen atoms
d)
4 oxygen atoms
11.
Which Chemical Equation is Balanced?
a)
CH₄+O₂------CO₂+2H₂O
b)
H₂+O₂-----2H₂O₄
c)
4Al+3O₂-----2Al₂O₃
12.
Bob puts 200 grams of ice into a pitcher with 900 grams of water. He gets distracted and comes back later to find that the ice has melted in the water. How many grams of water does Bob now have in the pitcher?
a)
200 g
b)
700 g
c)
1,100 g
13.
24 g of magnesium reacts with 38 g of fluorine to produce _____ g magnesium fluoride
a)
62
b)
38
c)
24
d)
14
14.
What is the law of conservation of mass?
a)
The amount of matter changes when reacted or changed.
b)
The mass of all reactants are changed during a physical or chemical change
c)
The mass of the reactants equals the mass of the products
d)
The mass of the products is different than the mass of the reactants.
15.
Endothermic reactions...
a)
release energy
b)
explode
c)
take in energy
d)
have higher energy in their reactants than the products
16.
Exothermic reactions
a)
have higher energy in their products than their reactants
b)
release energy
c)
get cold
d)
are synthesis reactions
17.
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.
18.
When CaCO3 is heated, it forms CaO and CO2. Which of these statements best describes the mass of the products if 100 g of CaCO3 is heated?
a)
The difference in the products’ masses is equal to the mass of the CaCO3
b)
The sum of the products’ masses is less than the mass of the CaCO3
c)
The mass of each product is equal to the mass of the CaCO3
d)
The sum of the products’ masses equals the mass of the CaCO3
19.
Molecule
a)
A group of atoms bonded together
b)
Basic unit of a chemical element
c)
Coefficient
d)
Subscript
20.
Suppose a reaction were to happen in an open container in a lab. During the reaction, the scientist observes the chemicals bubble, and produce a gas. During the analysis the scientist notices that the reactants weighed 20 g when he started, and the product weighed 18 g. Explain what happened.
a)
His chemical reaction defied the law of conservation of mass
b)
The product destroyed mass during the reaction
c)
The reactants created matter during the reaction
d)
The gas that was produced was not able to be weighed since the container was open.
21.
If four hydrogen atoms react with two hydrogen atoms, how many atoms will be in the product?
a)
6
b)
4
c)
8
d)
2
22.
10 g of a solid chemical reacts with a 10 g of a liquid chemical, the reaction bubbles and changes the color of the liquid. The colored liquid weighs 13 g, what can be concluded?
a)
The gas produced from the bubbles weighed 5 g
b)
The bubbles were evidence of 7 g of matter being destroyed
c)
The gas produced weighed 7 g
d)
The gas produced weighed 13 g
23.
Balance this equation.
_CF4 + _Br2 -- _CBr4 + _F2
_CF4 + _Br2 -- _CBr4 + _F2
a)
2,1,2,1
b)
1,2,2,1
c)
1,2,1,2
d)
2,2,2,2
24.
Balance this equation-
__P4 + __O2 --> __P2O3
__P4 + __O2 --> __P2O3
a)
it is already balanced
b)
2, 1, 3
c)
1, 2, 3
d)
1, 3, 2
25.
Mg + ___ HCl → MgCl2 + H2
a)
1
b)
2
c)
3
d)
4
100 %
