Question

section 3.2 changes in matter
in your textbook, read about physical change and chemical change.
what kinds of changes do these words indicate? write each word under the correct heading. use each word only once.
list of words: boil, burn, condense, corrode, crush, ferment, melt, rot, rust, tarnish, vaporize
physical change
1.
2.
3.
4.
5.
6.
7.
8.
chemical change
9.
10.
11.
12.
13.
14.
15.
16.
for each item in column a, write the letter of the matching item in column b.
column a

1. the new substances that are formed in a chemical reaction
2. a chemical reaction that involves one or more substances changing into new substances
3. shows the relationship between the reactants and products in a chemical reaction
4. states that mass is neither created nor destroyed in any process
5. the starting substances in a chemical reaction

answer the following question. write an equation showing conservation of mass of reactants and products.

1. in a laboratory, 178.8 g of water is separated into hydrogen gas and oxygen gas. the hydrogen gas has a mass of 20.0 g. what is the mass of the oxygen gas produced?

70 chemistry: matter and change • chapter 3 study guide

Explanation:

Step1: Recall law of conservation of mass

The law of conservation of mass states that mass is neither created nor destroyed in a chemical process. So, the mass of reactants is equal to the mass of products. In this case, water is being decomposed into hydrogen and oxygen. The mass of water is the sum of the mass of hydrogen and the mass of oxygen.
Let the mass of oxygen be $m_{O_2}$. The mass of water $m_{H_2O}=178.8\ g$ and the mass of hydrogen $m_{H_2} = 20.0\ g$.
The equation for conservation of mass is $m_{H_2O}=m_{H_2}+m_{O_2}$.

Step2: Solve for mass of oxygen

We can re - arrange the equation $m_{H_2O}=m_{H_2}+m_{O_2}$ to solve for $m_{O_2}$.
$m_{O_2}=m_{H_2O}-m_{H_2}$.
Substitute $m_{H_2O}=178.8\ g$ and $m_{H_2} = 20.0\ g$ into the equation.
$m_{O_2}=178.8 - 20.0$.
$m_{O_2}=158.8\ g$.

Answer:

The mass of the oxygen gas produced is $158.8\ g$.