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) Al ₂(SO₄)₃ Part 2: If there is 3 compounds of Al ₂(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 subscripts shows: ? The coefficient shows: ? The coefficient shows: ?

BALANCING CHEMICAL REACTIONS

Balancing Chemical Equations Beginner’s Guide - bozeman Brightstorm

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 Equations ___ Al(s) + ___ Br 2 (l) ---> ___ Al 2 Br 6 (s)

not 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 O H Mg Cl

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 Equations 4 Al(s) + 3 O 2 (g) ---> 2 Al 2 O 3 (s) This equation means 4 Al atoms + 3 O 2 molecules ---produces---> 2 molecules of Al 2 O 3 2 molecules of Al 2 O 3 AND/OR AND/OR 4 moles of Al + 3 moles of O 2 ---produces---> 2 moles of Al 2 O 3 2 moles of Al 2 O 3

Word equations for chemical reactions Practice Problems on Blue Sheet 1. 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(NO ₃) Sulfuric acid = H ₂(SO₄) Transition metals – Use of Roman numerals for + charge Polyatomic Ions Hydroxide = (OH ⁻¹) Carbonate = (CO ₃⁻²) Nitrate = (NO ₃⁻¹) Sulfate = (SO ₄⁻²) 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 B92AB1CD71DA186 For each example: 1. Identify the indicators that a reaction is happening. 2. Identify the types of reactions 3. Write the reaction (word equation) (23 minutes – elementary school level)