Chemical Compunds and Physical vs Chemical Changes

Chemical Compunds and Physical vs Chemical Changes

Elements and Compounds

• Element – any PURE substance, made of ONLY one kind of atom, anything found on the Periodic Table is, elements are represented by ONE capital letter, sometimes may be ONE capital and ONE lower  case letter

• Molecule – Two or more elements (can be the SAME or different) ex. O2 and H2O are BOTH molecules

• Compound – TWO or more DIFFERENT elements combined: just look for 2 DIFFERENT capital letters put together. ex. H2O = Compound  à  O2 or H2 = NOT a Compound

• ALL compounds are molecules, but NOT ALL molecules are compounds

Chemical Formulas and Counting Elements

• Capital Letters – EVERY capital letter represents a single element: DIFFERENT capital letters = DIFFERENT elements

• Lower Case Letters – belong to the capital letter in front of it

• Subscript – the small # that is sometimes seen behind the symbol, subscript is NEVER zero, if there is no # that follows a symbol then assume there is a 1, the small # tells you how many there are of the element in front of it

• Coefficient – the “Big” # in front of an element or compound, if no # in front assume that it is 1, MULTIPLY the # in front by all the small #’s that follow UNTIL you see a “+” sign

Multiple Choice

How many Elements are in

 $4H_2O$  

• 1

• 2

• 3

• 4

Multiple Choice

How many elements are in

 $C_6H_{12}O_6$  

• 1

• 2

• 3

• 4

Multiple Choice

How many Hydrogren atoms are in

 $H_2O$  

• 1

• 2

• 3

• 0

Multiple Choice

How many total atoms are in

 $H_2SO_4$  

• 4

• 5

• 6

• 7

Multiple Choice

How many Sodium (Na) atoms are in

 $6NaCl$  

• 4

• 5

• 6

• 7

Multiple Choice

A subscript is the small number below a(n) _____________ that tells the number of ___________ of that element.

• elements symbol, atoms

• atoms, element symbol

• subscript; protons

• compound, elements

Multiple Choice

What is a coefficient?

• The number on the right of the symbol.

• The large number on the left of the chemical compound.

• The small number below the element symbol.

• The small number after the chemical compound.

Physical Properites/Changes

•  Physical Properties – 3 Things ALWAYS Make it a Physical Property: 1. If it is a MEASUREMENT ex. Weight, height, density, mass, volume, specific heat, boiling/freezing/melting points. 2. If it explains WHAT IT IS ex. Magnetic, round(shape), size (big, small), color. 3. If it explains WHAT IT DOES ex. Good conductor, it bends, it shines.

• Physical Changes - Changes in a substance that do not involve a change in the identity or chemical makeup of that substance. All Changes in state of matter are physical changes. All physical changes are not necessarily accompanied by a chemical change.

Chemical Properties/Changes

• Chemical Changes - A change in a substance that involves a change in the identity or chemical makeup of that substance. All chemical changes are accompanied by a physical change.

• 6 Things ALWAYS Make it a Chemical

  Change/Reaction:

  Black → Burns

  Toilet  → Temperature Change

  Paper → Precipitate forms (New substance)

  Cleans → Color Change (sometimes)

  Good → Gas (Bubbles or Odor)

Multiple Choice

Is Condensing water vapor...

• Physical

• Chemical

Multiple Choice

Is combustion of gasoline...

• Physical

• Chemical

Multiple Choice

(Physical or Chemical) properties decribe matter?

• Physical

• Chemical

Multiple Choice

Oxygen is ordorless and colorless

• Physical

• Chemical

Multiple Choice

Diamonds are a very strong material

• Physical

• Chemical

Multiple Choice

Iron reacts with oxygen to form rust

• Physical

• Chemical

Multiple Choice

A piece of metal is magnetic

• Physical

• Chemical

Multiple Choice

Silver necklace tarnishes.

• Physical

• Chemical

Multiple Choice

Bases taste bitter

• Physical

• Chemical

Multiple Choice

Lighting a match

• Physical

• Chemical

Multiple Choice

Wood burning

• Physical

• Chemical

Multiple Choice

If you see ash, what kind of change do you think occured?

• Physical

• Chemical

Multiple Choice

Ice Melting

• Physical

• Chemical