Unit 7: Matter

Unit 7: Matter

Chapter 8

What is Matter?

Matter - Anything that has mass and takes up space

Multiple Select

Choose all of the examples of matter:

• water

• shoes

• wind

• text books

Classifying Matter

Classifying Matter

Matter can be divided into two categories:

1. Pure Substance
2. Mixture

Pure Substances

Pure Substance:

Has a constant composition and distinct chemical properties.

● All elements and compounds are pure substances
● A pure substance cannot be broken down further by physical means such as sorting, filtering, heating, or cooling

Element

Element: a pure substance that cannot be broken down
into simpler substances by chemical or physical means

● Made of a single type of atom from the periodic table
● Examples: Hydrogen (H), Oxygen (O), Sodium (Na)

Compounds and Molecules

● Molecule: A group of two or more of the same atoms chemically combined together.

○ Example: O2

● Compound: A substance that contains two or more elements chemically combined in a fixed proportion.

○ Example: H2O
○ Water always occurs in a 2:1 ratio

Match

Match the following pure substances:

• Element

• Molecule

• Compound

Hydrogen

O₂

NaCl

• Hydrogen

• O₂

• NaCl

Mixtures

Definition: A combination of various elements and compounds that can be physically separated.

Multiple Choice

Which is NOT an example of a mixture?

• cereal

• soup

• salt water

• sugar

Two Types of Mixtures

Heterogeneous Mixture

Heterogeneous mixture - the composition of matter is different (not uniformly mixed) throughout.

Ex.) Chicken noodle soup

One spoonful may contain noodles, chicken, and broth while another spoonful may only contain broth.

Homogeneous Mixture

Homogeneous mixture - the
composition of matter is the same
(uniformly mixed) throughout.

Most brass is made of 70 percent copper and
30 percent zinc.

If you cut a brass candlestick into ten pieces,
each piece would contain the same percentage of copper and zinc.

Elements, Compounds and Mixtures

Can you distinguish between atoms and molecules in these diagrams?

Practice Classification

Classify the following as a mixture or pure substance. Then determine whether it is a heterogeneous/homogeneous mixture or element/compound for a pure substance.

1. Table Salt (NaCl)
2. Salt Water (NaCl + H2O)
3. Sodium (Na)
4. Methane (CH4)
5. Air (N2 and O2)

Physical and Chemical
Properties

Physical and Chemical Properties

Physical Property

A quality or condition of a substance that can be observed or
measured without changing the substance’s chemical identity.

a. Examples: Color, shape, mass, length, temperature, melting/boiling point, etc.

Physical and Chemical Properties

Chemical Property

Any of a material's properties that become evident during or after a chemical reaction

** The material’s chemical identity is changed!!

a. Example: Rust, corrosion, flammable, “reacts with”

Physical/Chemical Properties Practice

Classify the following as either physical or chemical properties
and explain why.

● Blue Color
● Density
● Sour
● Boiling Point
● Reacts with Hydrochloric Acid

Physical Changes

Physical Change

Some properties of a material change but the composition of the material does not change. These changes are reversible.

● Examples: Melting, Mixing, Dissolving, cutting

Chemical Changes

Chemical Change

A change that produces matter with a different composition than the original matter. Classified as irreversible.

Examples: Rusting, Fermentation, burning, cooking

Evidence for Chemical Changes

● Color change
● Odor change
● Absorption or release of heat
● Emission of gas, light, and/or sound
● Bubbles form
● Solids form without temperature change (precipitation)
● NOTE: The only real way to tell whether there is a chemical change is if you test the properties before and
after.