Unit 1: Applications of Matter & Chemical Change
Lesson 4 - Word Equations & Types of Chemical Reactions
Approximate Lesson Length: 75 minutes
Subject Line for Email: SCI24U1L4
In this lesson, you will learn some of the universal language chemists use to describe what occurs during a chemical reaction. You will also learn about the four common reaction types.
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Word equations are used by chemists to describe what has happened in a chemical reaction. You were introduced to word equations in Science 14 when you learned about the reactants and products resulting from photosynthesis and respiration.
Word equations are always written in the same format.
|REACTANT 1 + REACTANT 2 --> PRODUCT 1 + PRODUCT 2|
Let's try an example and look at the word equation for photosynthesis...
carbon dioxide + water + sunlight (energy) ---> glucose + oxygen
If I read out the word equation for photosynthesis, I would say... "carbon dioxide and water and sunlight produce glucose and oxygen." Carbon dioxide, water and sunlight are the reactants. Glucose and oxygen are the products.
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Chemists have learned that there are patterns in how elements and compounds go together. This allows them to predict the product of an unknown chemical reaction and helps them to understand the behaviour of substances in a chemical reaction.There are four common reaction types: simple composition reactions, simple decomposition reactions, combustion reactions, and neutralization reactions.
1. Simple Composition Reaction - Two or more elements combine to form
a compound. Whenever you see two elements as reactants, you know that th reaction
is a simple composition reaction. The product is always a compound. Most simple
composition reactions are exothermic.
Element1 + Element2 --> Compound
2. Simple Decomposition Reaction - A reaction
that breaks a compound into its component elements is known as a simple decomposition
reaction. Whenever you see a compound as the only reactant, you know the reactioln
is a simple decomposition reaction. The products are always the elements. Most
decompostion reactions are endothermic.
Compound --> Element1 + Element2
3. Combustion Reactions - A reaction in which
a substance combines with oxygen to produce heat the light. This occurs when
fuel + oxygen --> carbon dioxide + water vapour + energy
4. Neutralization Reactions - A reaction in which an acid reacts with a base to produce a form of salt
and water. This is the type of reaction that occurs if you take an antacid.
acid + base --> salt + water
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In this lesson you learned how to read a word equation and how it represents what happens in a chemical reaction. You also learned about four common types of chemical reactions.
In this lesson we completed the following activities:
Section 1 - Word Equations
Section 2 - Types of Reactions
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In the next lesson, you will learn about the symbols that represent the various elements of the periodic table.
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Part A: Please use your science.connect2 Student Multimedia CD-ROM to answer the following questions in a word document. Launch The Chemical Reactions applet on your computer. In order to do this, open the CD, click on "PC", then click on "menu.exe". Next click on Chemical Reactions. Follow the instructions on each screen. Use the information on the applet to answer the questions below.
What Did You Discover?
1. Introduction to Chemical Reactions (a) List three examples of
2. Conservation of Mass (a) What is the name given to substances used in a chemical reaction?
(b) What is the name given to the substances produced during the chemical reaction?
(c) Summarize the Law of Conservation of Mass.
(d) How many atoms of hydrogen combine to form one molecule of hydrogen gas?
3. Signs of a Chemical Reaction (a) Define an exothermic chemical reaction and provide one example.
(b) Define an endothermic chemical reaction and provide one example.
(c) List four pieces of evidence that indicate a chemical reaction has taken place.
4. Simple Composition Reactions (a) What is a simple composition reaction?
(b) What happens to the energy in the chemical reaction that powers the space shuttle?
(c) Draw a diagram that summarizes the following reaction: 2H2(g) + O2(g) --> 2H20(l). Use a different colour or symbol to represent the oxygen and hydrogen atoms. (Complete this in your science binder, but you do not need to submit this).
(d) Write the word for the reaction in (c).
(e) Complete the following chart. Elements Number of Atoms in Reactants Number of Atoms in Products hydrogen oxygen (f) Does the chemical reaction in (e) obey the Law of Conservation of Mass? Explain.
5. Simple Decomposition Reactions (a) Define a simple decomposition reaction and give one example.
(b) Is the electrolysis of water an endothermic or exothermic reaction? Explain.
(c) Draw a sketch showing the decomposition of water. (Complete this in your science binder, but you do not need to submit this).
(d) Write the chemical equation that describes the decomposition of water.
(e) Write the word equation that describes the decomposition of water.
(f) Complete the following chart. Elements Number of Atoms in Reactants Number of Atoms in Products hydrogen oxygen (g) Does the chemical reaction in (f) obey the Law of Conservation of Mass? Explain.
6. Combustion of Fossil Fuels (a) Describe a combustion reaction.
(b) Is a combustion reaction endothermic or exothermic? How do you know?
(c) Draw a sketch that represents the combustion of methane. (Complete this in your science binder, but you do not need to submit this).
(d) Write the chemical equation for the combustion of methane.
(e)Write the word equation for the combustion of methane.
(f) Complete the following chart. Elements Number of Atoms in Reactants Number of Atoms in Products carbon hydrogen oxygen
(g) Does this reaction obey the Law of Conservation of Mass? Explain your response.
7. Printable Summary You may print the summary if you choose.
Part B: Pg. 49, Check Your Understanding questions 1 and 2.
Total Marks = 34
Please make sure you have handed in the following:
Attach your word document to the dropbox that contains your answers to parts A - B.
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© Rocky View Virtual School - Revised August 30, 2006