What do you already know about chemical and physical changes?

What do you already know chemical reactions?

Warm Up: Write in your notes

Chapter 9: Chemical Reactions

Writing word and skeletal equations

When the atoms of one or more substances are rearranged to form different substances.

Chemical Reactions:

CH4 + 2O2 ⇒ CO2 + 2H2O

Reactants: Starting substances Products: Ending Substances

+ Separates two or more reactants or products

⇒ Separates reactants from products

↔ Separates reactants from products and indicates a   reversible reaction

(s)  Identifies a solid state

(l)  Identifies a liquid state

(g)  Identifies a gaseous state

(aq)  Identifies a water solution (Aqueous)

Chemical Reaction Symbols:

Mass is neither created nor destroyed during a

chemical reaction

Law of the Conservation of

Mass

1. Energy change2. Color change3. Odor change4. Production of gas5. Formation of a solid

(precipitate)

Signs of a chemical change:

Energy either being gained or released as heat or light

Two types:◦Exothermic: Energy released by the

reaction We will see light or feel heat

◦Endothermic: Energy gained by the reaction

We will feel the reaction getting cold

Energy Change

Typically associated with another sign of a chemical change◦ Mixing of colors, diluting, etc, are not signs of a

chemical change

Color Change:

Rotting, baking, cooking, etc.

Odor Change:

Formation of bubbles, etc

◦ This is not caused by heating or boiling a substance.

Production of Gas

A solid is formed during the reaction, when adding or taking away energy from the rxn.

This solid is known as a precipitate.

It is NOT mean the freezing of a liquid into a solid.

Formation of a Solid:

Chemical Rxn in word format:

Solid Aluminum and liquid bromine react to produce solid aluminum bromide.

Word Equations:

Chemical reactions using chemical symbols and an arrow.

Al(s) + Br2(l) AlBr2(s)

Skeletal Equations

They are two different ways to write the same thing.

Solid Aluminum and liquid bromine react to produce solid aluminum bromide.

Al(s) + Br2(l) AlBr2(s)

Word and Skeletal Equations:

Reacts: tells us what is reacting with what We use a + to represent reacts/reacts with

Yields/To form: tells us what the product(s) is

We use an to represent yields/produces/to form

* We state the state of the matter for each substance. (solid, liquid, gas, or aqueous

Key Words:

Carbon monoxide gas and oxygen gas react to yield carbon dioxide gas.

CO(g) + O2(g) CO2(g)

Key Words:

Solid (s) Liquid (l) Gas (g) Aqueous (aq)

◦ Use the context clues of the word equation to determine the states of matter of the reactants and products.

States of Matter:

Notice that some of the elements have a 2 after them in their skeletal equations:

These are called diatomics:◦ These are elements exist in nature as two atoms

of the same element together, ONLY when they are not bonded to another element.

Diatomic Elements:

CO(g) + O2(g) CO2(g)

Al(s) + Br2(l) AlBr2(s)

There are 7 diatomics:

Diatomic Elements:

Aqueous Sodium hydroxide reacts with aqueous calcium bromide to form aqueous sodium bromide and solid calcium hydroxide.

Practice:

Solid zinc reacts with aqueous sulfuric acid to form hydrogen gas and solid zinc (II) sulfate.

Practice:

Fe(s) + O2(g) Fe203(s)

Practice:

Solid calcium oxide reacts with water to form solid calcium hydroxide.

Practice:

Gaseous sulfur dioxide and oxygen gas react to form sulfur trioxide gas.

Practice:

Solid sodium reacts with chlorine gas to form solid sodium chloride.

Practice:

NaCl(aq) + AgNO3(aq) NaNO3(aq) + AgCl(s)

Practice:

Please complete your ticket out the door, and turn into me before packing up.

HINT: Make sure you know the 7 diatomic elements tomorrow when you come in the door!

Ticket out the door: