Catalyst – November 9+23, 2009

What are the four ways you know a

chemical reaction has occurred?

Balance:. __Ca + __H2O

__Ca(OH)2 + __H2

Weekly Goal!

Today’s Agenda

CatalystChemistry Prom 2009 Day 1!

Practice and Work TimeExit Question

Today’s Objectives

SWBAT differentiate between combustion, synthesis, and decomposition reactions.

SWBAT predict the products of combustion, synthesis, and decomposition reactions.

Is this an example of a chemical reaction?

How do you know?

Evidence of Chemical Reactions

1. Formation of a gas2. Formation of a precipitate3. Temperature change4. Color change

Questions from Friday

SCENARIO: Juan wanted to see what would happen if he mixed water and salt together. After adding the salt and stirring, he observed that the salt seemed to disappear.

QUESTION: Did a chemical reaction occur?

Questions from Friday

SCENARIO: Jayde is interested in learning about two compounds, silver (I) nitrate and sodium chloride. She decides to dissolve each compound in water and mix them. When she does this, she sees a white solid form.

QUESTION: Did a chemical reaction occur?

Questions from Friday

SCENARIO: Antoinette puts 2 grams of salt into a beaker filled with a clear unknown liquid. The salt appears to disappear into the liquid.

QUESTION: Did a chemical reaction occur?

Questions from Friday

SCENARIO: William was curious about what would happen if he mixed zinc and hydrochloric acid. After doing so, the mixture bubbles and fizzes.

QUESTION: Did a chemical reaction occur?

Combustion, Synthesis, and Decomposition Reactions

Combustion, Synthesis, and Decomposition

Reactions

Chemical Reactions

There are 5 types of chemical hook-ups (reactions) at the prom this year.

1. Combustion2. Synthesis3. Decomposition4. Single-Replacement5. Double-Replacement

Boom goes the dynamite!

Key Point #1: A combustion reaction is when a hydrocarbon burns in the presence of oxygen, releasing heat and light The products will ALWAYS be CO2 and

H2OA hydrocarbon is any compound made of

only hydrogen and carbonEx: CH4, C2H4Is C50H102 a

hydrocarbon?

Combustion ExamplesPredict products and balance

1. CH4(g) + O2(g)

2. C2H2(g) + O2(g)

CO2(g) + 2 H2O(g)

4 CO2(g) + 2 H2O(g)

2

52

Practice

Write the chemical reaction for ethane gas (C2H6) burning in air.

1. If you see the word “BURNING,” that means it is a combustion reaction.

2. What are the reactants?C2H6 and O2

3. What are the products?CO2 and H2O

4. Last step: Balance! (don’t worry about phases for now)

C2H6 + O2 CO2 + H2O

Your Turn!

Write balanced equations for the following reactions:

1. Methane gas (CH4) combusts.

2. Butene gas (C4H4) burns in the air.

3. Ethyne gas (C2H2) goes through a combustion reaction.

Let’s come together

Key Point #2: A synthesis reaction is one in which two or more substances combine to form one new substance. A + B AB Two substances are at the Prom, dancing

alone…they decide to hook up…

Let’s come together….

Synthesis reaction – two more substances combine to form one new substance. Two substances dancing alone decide

to hook up… become a happy couple A + B AB

Man I’m lonely

Geez I could use a mate.

Satisfaction

Practice

Show the synthesis of solid aluminum and oxygen gas. What are the reactants?

Al + O2 (DIATOMIC ALERT!!!!) What are the products?

It’s a synthesis reaction, so we know Al and O are going to make a compound….

If the products aren’t in the question you need to KRISS KROSS TO figure them out!

Al (s) + O2 (g) AlOAl3+O2-Al2O3

Practice

Which reactions are synthesis reactions?

A. C + O2 CO2

B. CaO + H2O Ca(OH)2

C. H2O H2 + O2

D. 2Na + Cl2 2NaCl

E. Fe + CuSO4 FeSO4 + Cu

F. 2K3PO4 + 3H2SO4 3K2SO4 + 2H3PO4

A, B, and D

I don’t think this is working out…

Key Point #3: A decomposition reaction is one in which one substance breaks down into multiple substances, usually with the help of some kind of heat or energy AB A + B A couple at the Prom decides to break up

I don’t think this is working out… Decomposition reaction – one

substance breaks into multiple substances A couple decides…well it is time to

break up AB A + B

I don’t think this is

right for us…

I want to see other people Satisfaction!

Satisfaction!

Practice

Show the decomposition water after electricity has passed through it. What are the reactants?

Water! H2O What are the products?

It’s a decomposition reaction, so we know the elements in water are going to break apart

The question will specify if any compounds are formed

H2O H + O

Diatomic Alert!!!!

H2 + O2Don’t

forget to balance!

Practice – Your Turn!

1. Show the decomposition of ammonium nitrate into dinitrogen monoxide and water when the reactant is heated.

2. Show the decomposition of NaN3.

More Practice!

Which reactions are decomposition reactions?

A. C + O2 CO2

B. CaO + H2O Ca(OH)2

C. H2O H2 + O2

D. H2SO4 H2 + S + 2O2

E. Fe + CuSO4 FeSO4 + Cu

F. K3PO4 K3P + 2O2

C, D and F

Work Time – 3 Parts

A) Write one word problem and balanced chemical equation for each type of reaction (combustion, synthesis, decomposition) Examples of Hydrocarbons:

Propane (C3H8), Propene (C3H4), Propyne (C3H2) Pentane (C5H12), Pentene (C5H10), Pentyne (C5H8)

B) Book work: Pg 285, 14-20C) Early Finishers: Predict what the

chemical formulas for Octene and Octyne would be. Octane is C8H18.

Part A Examples

Combustion Word Problem: Carbon tetrahydride reacts with

oxygen gas to produce carbon dioxide and water. Balanced Equation: CH4 + 2 O2 CO2 + 2 H2O

Synthesis Word Problem: Hydrogen and oxygen react to

form water. Balanced Equation: H2 + O2 H2O

Decomposition Word Problem: Water decomposes to form

hydrogen and oxygen. Balanced Equation: H2O H2 + O2

Exit Question

1. Identify the following reactions as combustion, synthesis, or decomposition

CH4 + 2 O2 CO2 +2 H2O 2 H2NO3 2 H2 + N2 + 3 O2

2. Write the balanced chemical equation for the decomposition of solid magnesium oxide.