CM 02.2 Changes in Matter

LESSON 2: CHANGES IN

MATTER

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Lesson 2.2 Changes in Matter

• Define physical change and list several common

physical changes.

observation: orderly, direct information gathering
about a phenomenon

• Define chemical change and list several indications

that a chemical change has taken place.

• Apply the law of conservation of mass to chemical

reactions.

Lesson 2.2 Changes in Matter (cont.)

Matter can undergo physical and
chemical changes.

physical change

phase change

chemical change

law of conservation of mass

Physical Changes

• A change that alters a substance without

changing its composition is known as a
physical change.

Physical Changes

• A phase change is a transition of matter from

one state to another.

• Boiling, freezing, melting, and condensing all

describe phase changes in chemistry.

Chemical Changes

• A change that involves one or more

substances turning into new substances is
called a chemical change.

• Decomposing, rusting, exploding, burning, or

oxidizing are all terms that describe chemical
changes.

Conservation of Mass

• The law of conservation of mass states

that mass is neither created nor destroyed
in a chemical reaction, it is conserved.

• The mass of the reactants equals the mass of

the products.

massreactants = massproducts

Multiple Choice

When one substances turns into another, what kind of change has taken place? ​

• chemical reaction

• physical reaction

• extensive reaction

• nuclear reaction

Multiple Choice

The law of conservation of mass states that:

• Matter can be created and destroyed.

• Matter can be created but not destroyed.​

• The products of a reaction always have a greater mass than the reactants.​

• The products of a reaction must have the same mass as the reactants.​

1. Use the data in the table to answer the following questions.

a) How many grams of bromine reacted?
b) How many grams of compound were formed?

Practice Problems

Aluminum and Liquid Bromine Reaction

Substance

Before Reaction

After Reaction

Aluminum

10.3 g

0.0 g

Liquid Bromine

100.0g

8.2 g

Compound

0.0g

2. From a laboratory process designed to separate water into H2
and O2 gas, a student collected 10.0 grams of hydrogen and 79.4
g of oxygen.

a) How much H2O was originally involved in the process.

Practice Problems

3. A student carefully placed 15.6 g of Na in a reactor supplied with
an excess quantity of Cl2 gas. When the reaction was complete, the
student obtained 39.7 g of NaCl.
a) Calculate how many grams of Cl2 gas reacted.
b) How many grams of Na reacted?

Practice Problems

4. A 10.0-g sample of Mg reacts with O2 to form 16.6 g of MgO

(magnesium oxide). How many grams of O2 reacted?

Practice Problems

5. 106.5 g of HCl (g) react with an unknown amount of NH3 (g) to
produce 156.3 g of NH4Cl (s).

a) How many grams of NH3 (g) reacted?
b) Is the law of conservation of mass observed in the reaction?

Justify your answer.

Practice Problems

Categorize

Options (16)

crushing an aluminum can

melting ice

boiling water

dissolving sugar in water

breaking a glass

shredding paper

chopping wood

mixing sand and salt

rusting iron

burning wood

baking a cake

souring milk

digesting food

fermenting grapes

exploding fireworks

reacting vinegar with baking soda

Classify each example as a physical change or chemical change.

Physical Change

Chemical Change

Open Ended

Describe the results of a physical change and list three examples ​

of physical change.​

Open Ended

Describe the results of a chemical change. List four indicators of​

 chemical change.

Open Ended

In the complete reaction of 22.99 g of sodium with 35.56 g of chlorine, ​what mass of sodium chloride is formed?​

Open Ended

A 12.2 g sample of X reacts with a sample of Y to form 78.9 g of XY.​

 What is the mass of Y that reacted?​

Key Concepts

• A physical change alters the physical properties of a

substance without changing its composition.

• A chemical change, also known as a chemical reaction,

involves a change in a substance’s composition.

• In a chemical reaction, reactants form products.

• The law of conservation of mass states that mass is

neither created nor destroyed during a chemical
reaction; it is conserved.

massreactants = massproducts