Download Science24-UnitA-Section3.1-3.2

Science 24 - Unit A - Section 3.1-3.2
Name: ______________________________________
Word Equations
Chemical reactions are often represented using word equations. A word equation describes the reactants and
products of a chemical equation using the names of the chemicals.
Writing Word Equations
1. List the three things you have learned thus far about chemical reactions.
a. __________________________________________________________________________________
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b. __________________________________________________________________________________
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c. __________________________________________________________________________________
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2. Why do chemists use word equations to represent chemical reactions?
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3. Describe the standard format for writing a word equation for a chemical reaction.
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4. What is the purpose of the plus sign (+) in a word equation that represents a chemical reaction?
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Word Equations for Some Chemical Reactions
You are already familiar with a number of commonly occurring chemical reactions, such as the reaction for cellular
respiration. Read “Word Equations for some Chemical Reactions” on page 43 of the textbook. Familiarize yourself with
the word equations for some commonly occurring chemical reactions.
1. Write the word equation for the process of cellular respiration.
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a. Write out how you read this equation?
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b. How many reactants and products are there in the word equation?
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2. Write the word equation for the reaction that makes caves in areas of limestone.
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a. How many reactants and products are in this equation?
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3. Write the word equation for the addition of hydrochloric acid to mossy zinc.
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a. How does the word equation describe what you would observe if you actually added hydrochloric acid
to mossy zinc?
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Science 24 - Unit A - Section 3.1-3.2
Name: ______________________________________
Types of Reactions
When you study for school, do you put things that are similar together? Do you look for patterns when you try solving a
mathematics problem? Similarly, in chemistry, you can group chemical reactions together according to particular
patterns in which the reactions occur.
The most common types of reactions fall into four groups. You have already studied two of these types of
reactions—​combustion reactions ​and ​neutralization reactions​. The other two types of reactions that most common
chemical reactions fall under are ​simple composition reactions​ and s
​ imple decomposition reactions​.
Simple Composition Reactions
Define:
Simple Composition Reaction:
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1. List two reasons why chemists use patterns to group reaction types.
a. __________________________________________________________________________________
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b. __________________________________________________________________________________
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2. Write the word equation for the reaction of magnesium and oxygen.
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Reactants: _________________________________
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Products:
a. How many elements are used as reactants?
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b. What happens to the reactants during this reaction?
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3. Describe, in words, the general form of a simple composition reaction.
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4. Write the general form of a simple composition reaction using the letters A and B.
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5. Are most simple composition reactions exothermic or endothermic?
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6. Why is it important to know if a reaction is exothermic or endothermic?
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Simple Decomposition Reactions
Another type of chemical reaction is the simple decomposition reaction. In simple decomposition reactions, a
compound is separated into its elements. You have seen this type of reaction in Section 2 when you looked at the
electrolysis of water. This reaction requires energy to drive it.
Define:
Simple Decomposition Reaction:
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1. Write the word equation for the electrolysis of water.
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Reactants: _________________________________
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Products:
2. In a simple decomposition reaction, the products are always ______________________.
3. Write the general form for a simple decomposition reaction using the letters C and D.
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4. Most decomposition reactions are endothermic. What does this mean in terms of energy for these reactions?
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5. Describe how simple composition reactions compared to simple decomposition reactions.
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6. Read “Did You Know?” at the bottom of page 45 of the textbook. How do chemists today protect themselves
from the hazards that past experimenters, like Sir Humphry Davy, experienced?
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Combustion Reactions
You are most likely familiar with the next type of reaction—combustion reactions. Whenever you burn a fuel, a
combustion reaction occurs. Examples of combustion reactions include a wax candle burning; a match burning; logs in
a fireplace or fire pit burning; and natural gas, propane, or fuel oil burning in your furnace.
1. Write the word equation for the combustion of gasoline in a car.
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Reactants: _________________________________
Products:
_________________________________
2. List the six materials shown in Figure 3.7 that are produced from petroleum.
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3. Read “Did You Know?” on page 48 of the textbook. Which process appears to be a better use of fossil
fuels—using 76 L of petroleum to move a car 485 km or using 76 L of petroleum to produce all the goods listed
in the reading?
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Neutralization Reactions
If you have ever taken an antacid to relieve an upset stomach, then you have felt the effects of a neutralization
reaction. In this case the antacid (a base) neutralizes the excess stomach acid (an acid) to form a salt and water.
1. Write the word equation for a general neutralization reaction.
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Reactants: _________________________________
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Products:
2. Write the word equation for the neutralization of stomach acid with magnesium hydroxide.
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a. One of the products is water. What is the general name for the other product?
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3. Name the substance forming the white cloud in the picture on page 49 of the textbook.
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a. Which two substances are combining to form this compound?
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Check your Understanding
1. Under each, write what you would say as you read the equation.
a. solid zinc + hydrochloric acid → hydrogen gas + zinc chloride
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b. ammonium nitrate + sodium hydroxide → ammonium hydroxide + sodium nitrate
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c. hydrochloric acid + sodium acetate → acetic acid + sodium chloride
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2. Read this list of chemical reactions. Identify the ones that show simple composition reactions.
a. methane gas + oxygen gas → carbon dioxide + water
b. solid calcium + oxygen gas → solid calcium + oxide
c. solid sodium chloride → solid sodium + chlorine gas
d. solid sodium hydroxide + liquid acetic acid → sodium acetate (a salt) + water
e. solid magnesium + oxygen gas → magnesium oxide
f.
hydrogen gas + oxygen gas → water
3. Explain the following two equations.
a. A + B → AB
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b. CD → C + D
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c. Which one shows the general format of a simple composition reaction?
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d. Which one shows a simple decomposition reaction?
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