Agenda 11/18 Chemical Reactions

• Objective: To predict the products of chemical reactions• Warm-up: Atoms in a compound

• Balancing Equations • Steps• Example Problems • Word equations for chemical reactions

• Important formulas and names• Balancing equations practice

• Chemical reactions- Bill Nye• Indicators of chemical reactions

• Return Test: • Qualifiers – wiki page

Homework: See homework assignment sheet

Warm-up: Small sheet – Hand in

• Part 1: Name the compounds and specify the number of atoms of each element:

• Ca(SO₄) Na₂(SO₄) Al₂(SO₄)₃

• Part 2: If there is 3 compounds of Al₂(SO₄)₃, how many atoms are there of each type of element?

Warm-up: Different compounds

• Compare water (H₂O) and hydrogen peroxide (H₂O₂)? • How are these compounds similar? • What is hydrogen peroxide used for? • Why do you think they are different?

What is the difference between carbon monoxide (CO) and carbon dioxide (CO₂)?

• How are these compounds similar? • What is the difference in properties?• Why do you think that they are different?

Coefficients vs. Subscripts• Subscripts= number of atoms of an element in a specific

compound

What happens when we change the subscripts in a compound?

• Coefficients = number of compounds • Multiplier when determining number of atoms

Subscripts vs. Coefficients

• The subscripts shows: ?

• The coefficient shows: ?

BALANCING CHEMICAL REACTIONS

Balancing Chemical Equations • Beginner’s Guide - bozeman• http://www.youtube.com/watch?v=_B735turDoM

• Brightstorm• http://www.youtube.com/watch?v=YAutl-G7g4A

Because of the principle of the conservation of matter,

an equation must be balanced.

It must have the same number of atoms of the same kind on both sides.

Introduction: Chemical Equations

Lavoisier, 1788

Balancing EquationsBalancing Equations

___ Al(s) + ___ Br2(l) ---> ___ Al2Br6(s)

• When balancing a chemical reaction Coefficients are added in front of a compounds to balance the reaction, but

you may not change the subscripts.

• Changing the subscripts changes the compound.

Important in Balancing Equations

Why balance chemical reactions?• Law of Conservation of Matter:

• matter is neither created nor destroyed in __ ________ _________.

• In a chemical reaction, atoms are combined, separated and/or rearranged.

• No atoms are lost or gained in a chemical reaction.

In a balanced reaction• Chemical reactions are shown with symbols (formulas in

an equation) • Starting materials = reactants • Produces, yields = arrow• End materials = products

• # atoms of reactants= # atoms of products

Steps to balance equations:• Start with correct formulas for the compounds.

• Never, never change the formula (subscripts) • Put a box around the formulas as a reminder.

• Count how many atoms of each type of element on each side of the equation.

• Use multipliers (called coefficients) in front of the formulas on each side of the equation until the number on each side matches up.

Methane and oxygen produces carbon dioxide and water. • Write the correct formulas (skeleton equations)

Notes: Methane and oxygen produces carbon dioxide and water.1. Correct formulas and symbols.• Put box around each formula.

2. Count the number of atoms on both sides of the equation

Methane + oxygen carbon dioxide + water

Notes: Methane and oxygen produces carbon dioxide and water.3. Balance the equation using coefficients.(Coefficients are multipliers in front of the compounds)

4. Use the smallest whole number possible.

Magnesium hydroxide and hydrochloric acid reacts to produce magnesium chloride and water.

• Write the skeleton equation (formulas)

Example: Magnesium hydroxide and hydrochloric

acid reacts to produce sodium chloride and water.

Write the formulas: Mg(OH)₂ + HCl → MgCl₂ + H₂O

Count the atoms on each side.Mg(OH)₂ + HCl → MgCl₂ + H₂O

OH MgCl

• Use multipliers (coefficients) in front of the compounds to have the same number of atoms of each type on both sides of the equation (both sides of the arrow).

Mg(OH)₂ + 2 HCl → MgCl₂ + 2 H(OH)

Aluminum reacts with oxygen to produce aluminum oxide

Chemical EquationsChemical Equations4 Al(s) + 3 O2(g) ---> 2 Al2O3(s)

This equation means

4 Al atoms + 3 O2 molecules ---produces--->

2 molecules of Al2O3

AND/OR

4 moles of Al + 3 moles of O2 ---produces--->

2 moles of Al2O3

Word equations for chemical reactions

• Practice Problems on Blue Sheet1. Names to formulas

2. Balancing equations

3. Recipe (basic proportions)

4. Identify types of reactions

5. Identify states of matter

6. Indicators of chemical change?

Names & Formulas Review Word equations for chemical reactions

• Acids: Starts with H • Hydrochloric acid = HCl• Nitric acid = H(NO₃)• Sulfuric acid = H₂(SO₄)

• Transition metals – Use of Roman numerals for + charge• Polyatomic Ions

• Hydroxide = (OH⁻¹)• Carbonate = (CO₃⁻²)• Nitrate = (NO₃⁻¹)• Sulfate = (SO₄⁻²)

• Diatomic molecules • Heck No Halogens

• Zinc + hydrochloric acid Zinc chloride and hydrogen

• Copper II chloride + sulfuric acid copper II sulfate + water + carbon dioxide

• Magnesium oxide + nitric acid magnesium nitrate + water

• Zinc + sulfuric acid Zinc sulfate + hydrogen

Your turn #5-10

Bill Nye- Chemical Reactions

http://www.youtube.com/watch?v=66kuhJkQCVM&list=PL9B92AB1CD71DA186

For each example:

1. Identify the indicators that a reaction is happening.

2. Identify the types of reactions

3. Write the reaction (word equation)

http://www.youtube.com/watch?v=PlwuxpMh8nk (23 minutes – elementary school level)