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: H2O• Vinegar: CH3COOH• Carbon Dioxide: CO2

• Baking Soda: NaHCO3

• Sugar: C12H22O11

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…