3/15/12 – Bell ringer• Water freezing or boiling is

not chemical reaction. Why?

• Hold on to 4 bell ringers as we will turn them in at the end of notes

Chapter 23 – Chemical Reactions

23.1 – Chemical Changes

Objectives• 1. Identify the reactants and products in

a chemical reaction.• 2. Determine how a chemical reaction

satisfies the law of the conservation of matter.

• 3. Determine how chemists express chemical changes using equations

Chemical Reaction

• A change in which one or more substances are converted to new substances–Reactants – the substances that react–Products – the new substances

produced

Different Reactions• Chemical reactions – use the

ELECTRONS to form new substances• Nuclear reactions - use the

NUCLEUS to form new substances

• What does a chemical reaction look like?

Chemistry Kitchen

Chemistry Kitchen

REACTANTS PRODUCTS

Think about it…• If you burned a piece of paper, you end

up with a pile of ashes.• Once burned, is there…

– More mass?– Same mass?– Less mass?

• Why?

Conservation of Mass• Law that states in a chemical

reaction, matter is not created or destroyed– Antoine Lavoisier experimented

with mercury (II) oxide and heat– He found mass of products (liquid

mercury and oxygen gas) equaled mass of reactants

Chemical Equation• Uses chemical formulas and symbols to

describe a chemical reaction and the product(s) it produces– Chemical formula expresses the

relationship between elements in the compound and molecules they make up

Chemical Equation

Reactants (left) → Products (right)Arrow means “yields”

SnO2(s) + 2 H2(g) → Sn(s) + 2 H2O(g)

CH4(g) + 2 O2

(g) → CO2(g) + 2 H2O(g)

Coefficients• Numbers which represent the

number of units of each substance in a reaction– Knowing coefficients of chemical

reactions allows chemists to use the correct amount of reactants to predict the amount of products (law of conservation applies)

Example

Writing equations• Subscripts = Numbers which represent

the number of atoms in a molecule of a particular element

• Symbols used to show state of reactants–(s) solids–(aq) aqueous–(l) liquid–(g) gas

Volcano with a Twist• Reactants?

• Products?

• Equation:NaHCO3 ( ) + CH3COOH ( ) CH3COO-Na+ ( ) + H2O ( ) + CO2 ( )

• States?• Conservation?

Exit slip on BR paper• SnO2(s) + 2 H2(g) → Sn(s) + 2 H2O(g)

• What are the reactants?• What are the products?• How is matter conserved/equalled out?• What changed?

– (Compounds and States)

In-class Assignment/Homework• 23.1 WKT