atoms vs. molecules atom – the smallest unit of an element that maintains the properties of that...

Atoms vs. Molecules

• Atom – the smallest unit of an element that maintains the properties of that element.

• Ex: C, O, He, Hg

• Molecule – two or more atoms joined in a definite ratio.

• Ex: CO2, O2, NaCl, C6H12O6

For a molecule to be a compound it must contain atoms of at least two different elements.

Counting Atoms Practice

K2CO3

Ca(C2H3O2)2

NaBr

Al(OH)3

2 6

15 7

Parts of a Chemical Equation

YIELDS

COEFFICIENT SUBSCRIPT

Reactants MUST Equal Products (Law of Conservation of Matter)

Counting Atoms Practice with Coefficients

4K2CO3

2Ca(C2H3O2)2

12NaBr

4Al(OH)3

6Ba(MnO4)2

5Ga2(Cr2O7)3

24 24

30

145

28

66

Are They Balanced??

Reactants MUST Equal Products (Law of Conservation of Matter)

Na2O2 + H2O4NaOH + O2

Zn + AgNO3

Zn(NO3)2 + 2AgAl + MnO

Al2O3 +3Mn

NH3 +HClNH4Cl

NOT BALANCED7 14

6

6

3

11

8

6

NOT BALANCED

NOT BALANCED

BALANCED

How Will I Know??

Signs of a Chemical Reaction

Chemical Reaction Definition: The process of one or more substances changing to

produce new substances. (VERY SIMILAR to a Chemical Change!)

Gas Formation; Precipitate formation (solids settle to the bottom); Thermal Energy Change (heat/light given off); Color Change; Effervesces (BUBBLES!!);

Odor (smell)

What happens to chemical bonds during a chemical reaction?

• Bond are broken down.• Atoms are rearranged.• New bonds are formed to create

new substances with different physical and chemical properties.

How Can We Manipulate Reactions??Speed Up

Slow Down

Law of Conservation of Energy…Whatever Energy you START with you MUST finish with…

Energy CANNOT be created or destroyed!!

Increase the temperature; Increase the concentration of the reactant; Grind reactants into smaller pieces (reduce the surface

area); Agitate (stir quickly); add a Catalyst (something to speed up a reaction)

Decrease the temperature; Decrease the concentration of the reactant; Use large/solid pieces of reactants);

Add an inhibitor (something to slow a reaction)

Romantic Reactions

See how some of your favorite characters react together…there will be laughter, love, tears, and anger.

Types of Chemical Reactions

As told by our media addictions…

Synthesis Reaction• Two or more simple substances

combine to form a more complex substance.

Decomposition Reaction• A complex substance breaks down

into two more simpler substances.• Reverse of a synthesis reaction.

Single Replacement Reaction• A single element replaces one element in a

compound.• The product of a single replacement reaction

are a new compound and a single element.

Double Replacement Reaction• Two new compounds form.

• The element with the positive oxidation state in one compound changes places

with the positive oxidation state element in the other compound.

Practice – Balancing Equations

1. Na2O2 + H2O 4NaOH + O2

2. Zn + AgNO3 Zn(NO3)2 + 2 Ag

3. Al + MnO Al2O3 + 3Mn