Chemistry Sec1.4.ppt

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1.4 Problem Solving in Chemistry >

Chapter 1

Introduction to Chemistry

1.1 The Scope of Chemistry 1.2 Chemistry and You

1.3 Thinking Like a Scientist

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1.4 Problem Solving in Chemistry > CHEMISTRYCHEMISTRY & & YOUYOU

How does having a plan make problem

solving easier?

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Skills Used in

Solving Problems

Skills Used in Solving Problems

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1.4 Problem Solving in Chemistry > Skills Used in Skills Used in

Solving Problems

Problem solving is a skill you use all the

time.

• A shopper must make many decisions. Some of those are based on data, like the information on a food label.

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Skills Used in

Solving Problems

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Effective problem solving always involves developing a plan and then

A. evaluating the plan.

B. doing the calculations.

C. making an estimate.

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A. evaluating the plan.

B. doing the calculations.

C. making an estimate.

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1.4 Problem Solving in Chemistry > Solving Numeric Solving Numeric

Problems

Solving Numeric Problems

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Solving Numeric

Problems

• Most word problems in chemistry require math because measurement is such an important part of chemistry.

• The techniques used in this course to solve numeric problems are conveniently

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Problems

The steps for solving a numeric

word problem are analyze,

calculate, and evaluate.

Analyze Evaluate

2

1 3

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Solving Numeric

Problems

• First determine where you are starting from (identify what is known) and where you are going (identify what is unknown).

Analyze

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Problems

• First determine where you are starting from (identify what is known) and where you are going (identify what is unknown).

• If you expect the answer (the unknown) to be a number, you need to determine what unit(s) the answer should have.

• Make a plan for using what is known to arrive at the unknown.

Analyze

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Solving Numeric

Problems

• For some problems, you will have to convert a measurement from one unit to another.

• For other problems, you may need to

rearrange an equation before you can solve for an unknown.

Calculate

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Problems

After you calculate an answer, you

should evaluate it.

Evaluate

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Solving Numeric

Problems

After you calculate an answer, you

should evaluate it.

Evaluate

3

• Is the answer reasonable? • Does it make sense?

• Did you copy the data correctly?

• Did you choose the right equations?

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1.4 Problem Solving in Chemistry > SampleSample Problem 1.1Problem 1.1

Estimate Walking Time

You are visiting Indianapolis. You decide to walk from the Indiana State Capital to the Murat Centre for an

afternoon performance. According to the map, the shortest route from the capital to the theater is 8 blocks. How many minutes will the trip take if you can walk 1 mile in 20 minutes?

Start

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Sample Problem 1.1

This problem is an example of a conversion

problem. One unit of measure (blocks) must be expressed in a different unit (minutes).

KNOWNS

distance to be traveled = 8 blocks

walking speed = 1 mile/20 minutes

1 mile = 10 blocks

UNKNOWN

time of trip = ? minutes

Analyze List the knowns and the unknown.

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Divide the number of

blocks to be traveled by the number of blocks in 1 mile.

Calculate Solve for the unknown.

2

1 mile 10 blocks

8 blocks  = 0.8 mile

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Multiply the number of miles by the time it takes to walk 1 mile.

Calculate Solve for the unknown.

2

Notice how the units cancel.

20 minutes 1 mile

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• The answer seems reasonable, 16 minutes to walk 8 blocks.

• The answer has the correct unit. • The relationships used are correct.

Evaluate Does the result make sense?

3

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Matthew has been collecting quarters in a jar. He has 176 quarters. What is the value of the coins in his jar?

1 dollar 4 quarters

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Solving Nonnumeric

Problems

Solving Nonnumeric Problems

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1.4 Problem Solving in Chemistry > Solving Nonnumeric Solving Nonnumeric

Problems

Not every word problem in chemistry

requires calculations.

• Some problems ask you to apply the concepts you are studying to a new situation.

• You still need to identify what is known and what is unknown.

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Solving Nonnumeric

Problems

The steps for solving a

nonnumeric problem are analyze

and solve.

Analyze Solve

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1.4 Problem Solving in Chemistry > CHEMISTRYCHEMISTRY & & YOUYOU

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CHEMISTRY & YOU

CHEMISTRY & YOU

Pick a game you like to play or a type

of puzzle you enjoy solving. How does

having a plan make playing the game

or solving the puzzle easier?

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1.4 Problem Solving in Chemistry > SampleSample Problem 1.2Problem 1.2

Scheduling Classes

Manny needs to schedule his classes for next year. The school day is divided into seven periods, and he must take Algebra II, Art, Chemistry, English, History, and Physical Education. Using the information from the course catalog, find a way for Manny to schedule all his classes.

 Algebra II is offered during either 1st or 2nd period._{Algebra II is offered during either 1st or 2nd period.}

 Art is offered during 2nd period only._{Art is offered during 2nd period only.}

 _{Chemistry is offered during either 3rd or 6th period.}_{Chemistry is offered during either 3rd or 6th period.}  English is offered during either 6th or 7th period._{English is offered during either 6th or 7th period.}

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• Manny must take lunch during 5th period.

• Art is only available during 2nd period. • Physical Education is only available

during 4th period.

Analyze Identify the relevant concepts.

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Place lunch, Art, and Physical Education into Manny’s schedule.

Solve

Apply the concepts to this problem.

2

Manny’s Schedule 1st period

2nd period Art 3rd period

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Fill the remainder of the classes into Manny’s schedule.

Solve

Apply the concepts to this problem.

2

Manny’s Schedule 1st period Algebra II

2nd period Art

3rd period Chemistry 4th period P.E.

5th period Lunch 6th period English 7th period History

Since Art is only

available during 2nd period, Manny must take Algebra II during 1st period. Since P.E. is only available

during 4th period, he must take History

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The steps for solving a nonnumeric

problem are:

A. solve and evaluate.

B. analyze, solve, and evaluate.

C. analyze and solve.

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The steps for solving a nonnumeric

problem are:

A. solve and evaluate.

B. analyze, solve, and evaluate.

C. analyze and solve.

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1.4 Problem Solving in Chemistry > Key ConceptsKey Concepts

The steps for solving a nonnumeric

Effective problem solving always involves developing a plan and then implementing that plan.

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Chemistry Sec1.4.ppt

How does having a plan make problem

solving easier?

Skills Used in Solving Problems

Problem solving is a skill you use all the

time.

Solving Numeric Problems

The steps for solving a numeric

word problem are analyze,

calculate, and evaluate.

Analyze

Analyze

Calculate

After you calculate an answer, you

should evaluate it.

Evaluate

After you calculate an answer, you

should evaluate it.

Evaluate

Estimate Walking Time

Analyze List the knowns and the unknown.

Calculate Solve for the unknown.

Calculate Solve for the unknown.

Evaluate Does the result make sense?

Solving Nonnumeric Problems

Not every word problem in chemistry

requires calculations.

The steps for solving a

nonnumeric problem are analyze

and solve.

Pick a game you like to play or a type

of puzzle you enjoy solving. How does

having a plan make playing the game

or solving the puzzle easier?

Scheduling Classes

Analyze Identify the relevant concepts.

Solve

Solve

The steps for solving a nonnumeric

problem are:

The steps for solving a nonnumeric

problem are:

END OF 1.4