Elements, Compounds, and Mixtures

Pure Substances

Matter that has a uniform and unchanging composition

What are the only two things that are considered pure substances?

Elements and compounds

What is an element?

A pure substance that CANNOT be separated by chemical or physical means

What is the simplest form of matter that have unique properties?

Elements

What 3 does each element have?

unique name, properties, and symbol

Examples of Elements

Na, K, C, H

What are compounds?

Two or more elements that are combined CHEMICALLY in foxed proportions

What’s the difference between compounds and elements separation wise?

Compounds CAN be separated chemically

What type of properties do compounds have?

new properties that are different from the elements that make it up

Example of a compound:

Sodium (Na) + Chlorine (Cl₂) → Sodium Chloride (NaCl)

What are atoms?

the smallest identifiable unit of an element

What do atoms do with the elements properties?

They maintain the unique properties

What is a molecule/formula unit

the smallest identifiable unit of some elements or all compounds.

Molecules of an element contain what?

two or more of the SAME atom bonded together. 

Molecules of compounds contain what?

two or more DIFFERENT atoms bonded together. 

Law of Multiple Proportions

When the same elements combine to form compounds, they do so in simple whole number ratios

Ex: of Law of Multiple Proportions

CO, CO₂, H₂O, H₂O

Law of Definite Proportions

A chemical compound always has the exact same proportion of elements by mass

Equation of Law of Definite Proportions

Percent composition = mass of element x 100
                      mass of compound

What is a mixture?

Two or more pure substances are physically combined

In mixtures, what does each substance do?

Retains its own chemical properties

Do mixtures maintain the same proportions in every sample?

No

Heterogeneous Mixture

A mixture that does not have a uniform composition throughout (substances remain distinct) 

Ex: of Heterogeneous Mixture

Sand and water

What is a Homogeneous Mixture

A mixture that has a uniform composition throughout (substances blend)

What is a liquid homogeneous mixture often called?

A solution

Ex of a liquid homogeneous mixture/solution

Salt water (saline solution)