3/15/12 - Bellringer

3/15/12 - Bellringer• What kind of reactions can you think of?

(Think outside the box!)

• Turn in 4 bellringers from this week when finished.

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

Chapter 23 – Chemical Reactions

23.1 – Chemical Changes

Chemical Reactions• 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• Conservation of Mass - a 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

3/19/12 - Bellringer• Boiling or freezing water is NOT a

chemical reaction. Why?

• Turn in 4 bellringers from last week if absent Thursday.

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 theymake up

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

Subscripts and Symbols• 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?

Notes Supplement• Chemical equations will look similar to…

#AB(state) + # CD(state) → #AC(state) + #BD(state)

Reactants (left) → Products (right)

Arrow means “yields”

Practice

• SnO2(s) + 2 H2(g) → Sn(s) + 2 H2O(g)

• CH4(g) + 2 O2

(g) → CO2(g) + 2 H2O(g)

In class assignment / homework:• Section 1 Reinforcement

• Balancing Chemical Equations PART A AND B ONLY

Closure Question

• 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)