ELEMENTS, COMPOUNDS, AND MIXTURES

A Meteorite may travel 400 M km to reach Earth. BUT, the particles of iron in a meteorite, a steel spoon and braces are all alike!

Elements, the Simplest Substances

• • Element: a pure substance that CANNOT be separated into simpler substances by physical or chemical means. Examples: Iron, Gold, Mercury, Nickel, Cobalt.

Elements, the Simplest Substances

• • • A pure substance: contains only ONE TYPE of particle.

These particles are called ATOMS!

Example: Every atoms in a 5 g nugget of gold is like every other atom of gold!

Properties of Elements

• • • • • •

PHYSICAL

PROPERTIES: Boiling Point Melting Point Density Texture Color • • •

CHEMICAL PROPERTIES:

Reactivity with Acid Flammable

Identifying Elements by Their Properties

• • • Elements can be identified by their properties.

Example: Look on page 57 – Figure 2. What element has a Melting Point of 1,535 degrees Celsius and combines slowly with O in the air?

ANSWER:_________________

Classifying Elements by Their Properties

• • • • • Elements are grouped into categories by the properties they share.

3 Major Categories: METALS: Shiny, good conductors NONMETALS: Dull, poor conductors METALLOIDS: Have properties of both metals and nonmetals! 

Compounds

• • • • Compounds: 2 or more elements that are CHEMICALLY combined!

They combine through a chemical reaction.

In Figure 1: page 60 – Mg + O = MgO Magnesium Oxide (MgO) is a NEW substance with different characteristics!

Examples of Compounds

• • • • • • Table Salt: NaCl Water: H 2 O Vinegar: CH 3 COOH Carbon Dioxide: CO 2 Baking Soda: NaHCO 3 Sugar: C 12 H 22 O 11

Compounds vs Elements

• •

COMPOUNDS

Salt: a safe seasoning for you to eat.

• • •

ELEMENTS

Sodium: soft, silvery white metal that reacts violently with water.

Chlorine: poisonous, greenish yellow gas

Breaking Down Compounds

• • • • Compounds can be broken down into elements or simpler compounds.

HOW??? – By Chemical Changes!

Example: Carbonic Acid (gives soda “fizz”) breaks down into Carbon Dioxide and Water just when you open a soda.

Carbon Dioxide and Water can be broken down by chemical changes.

MIXTURES

• • • Mixture: a combination of two or more substances that are NOT chemically combined.

NO chemical change happens when a mixture is made.

EX: Pizza, Chex Mix, Lucky Charms, Salad.

Solutions

• • • • Solutions: a mixture that appears to be a single substance. It is composed of particles of two or more substances.

SOLUTE + SOLVENT = SOLUTION Is Dissolved + Dissolves It Hot Cocoa Mix + Water = Hot Cocoa

Concentration of Solutions

• • • Concentration: a measure of the amount of solute dissolved in a solvent.

Concentrated: TOO much solute Dilute: TOO little solute

Suspensions

• Suspension: a mixture in which particles of a material are dispersed throughout a liquid or gas but are large enough to settle out.

Colloids

• • • Colloid: a mixture in which the particles are dispersed throughout but are not heavy enough to settle out.

The particles in a colloid are much smaller than in a suspension.

Examples: Milk, Mayonnaise, Stick Deodorant, and Jello

I Can Statements…

• • • • • I can tell you that an element is… I can tell you that a compound is… I can tell you that a solution is… I can tell you that a suspension is… I can tell you that a colloid is…