1.4 Problem Solving in Chemistry > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chapter 1 Introduction to Chemistry 1.1 The Scope of Chemistry 1.2 Chemistry and You 1.3 Thinking Like a Scientist 1.4 Problem Solving in Chemistry

1.4 Problem Solving in Chemistry > 2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Solving Numeric Problems What are the steps for solving numeric problems?

1.4 Problem Solving in Chemistry > 3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 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 organized into a three-step problem-solving approach.

1.4 Problem Solving in Chemistry > 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Solving Numeric Problems The steps for solving a numeric word problem are analyze, calculate, and evaluate. AnalyzeEvaluate 213 Calculate

1.4 Problem Solving in Chemistry > 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Solving Numeric 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 1

1.4 Problem Solving in Chemistry > 6 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 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 2

1.4 Problem Solving in Chemistry > 7 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 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? Check that your answer has the correct unit(s) and the correct number of significant figures.

1.4 Problem Solving in Chemistry > 8 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 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? Assume that 10 blocks equals 1 mile. Start Finish

1.4 Problem Solving in Chemistry > 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 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. 1

1.4 Problem Solving in Chemistry > 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Divide the number of blocks to be traveled by the number of blocks in 1 mile. Calculate Solve for the unknown. 2 Sample Problem mile 10 blocks 8 blocks  = 0.8 mile The relationship 1 mile = 10 blocks can be interpreted as “1 mile per 10 blocks.”

1.4 Problem Solving in Chemistry > 11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Multiply the number of miles by the time it takes to walk 1 mile. Calculate Solve for the unknown. 2 Sample Problem 1.1 Notice how the units cancel. 20 minutes 1 mile 0.8 mile  = 16 minutes

1.4 Problem Solving in Chemistry > 12 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 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 Sample Problem 1.1

1.4 Problem Solving in Chemistry > 13 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Matthew has been collecting quarters in a jar. He has 176 quarters. What is the value of the coins in his jar?

1.4 Problem Solving in Chemistry > 14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 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 176 quarters  = 44 dollars

1.4 Problem Solving in Chemistry > 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Solving Nonnumeric Problems What are the steps for solving nonnumeric problems?

1.4 Problem Solving in Chemistry > 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 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. You still need to make a plan for getting from the known to the unknown.

1.4 Problem Solving in Chemistry > 17 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Solving Nonnumeric Problems The steps for solving a nonnumeric problem are analyze and solve. AnalyzeSolve 21

1.4 Problem Solving in Chemistry > 18 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 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? In solving a crossword puzzle, you may try to fill in all the “down” clues before attempting the “across” clues. Or you may first try to complete the fill-in-the-blank clues before moving on to the more difficult clues.

1.4 Problem Solving in Chemistry > 19 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 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. History is offered during either 4th or 7th period. History is offered during either 4th or 7th period. Physical Education is offered during 4th period only. Physical Education is offered during 4th period only. Lunch is scheduled for 5th period. Lunch is scheduled for 5th period.

1.4 Problem Solving in Chemistry > 20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 1.2 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. 1

1.4 Problem Solving in Chemistry > 21 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Place lunch, Art, and Physical Education into Manny’s schedule. Solve Apply the concepts to this problem. 2 Sample Problem 1.2 Manny’s Schedule 1st period 2nd periodArt 3rd period 4th periodP.E. 5th periodLunch 6th period 7th period

1.4 Problem Solving in Chemistry > 22 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Fill the remainder of the classes into Manny’s schedule. Solve Apply the concepts to this problem. 2 Sample Problem 1.2 Manny’s Schedule 1st periodAlgebra II 2nd periodArt 3rd periodChemistry 4th periodP.E. 5th periodLunch 6th periodEnglish 7th periodHistory 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 during 7th period.

1.4 Problem Solving in Chemistry > 23 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The steps for solving a nonnumeric problem are: A.solve and evaluate. B.analyze, solve, and evaluate. C.analyze and solve. D.analyze, calculate, and evaluate.

1.4 Problem Solving in Chemistry > 24 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The steps for solving a nonnumeric problem are: A.solve and evaluate. B.analyze, solve, and evaluate. C.analyze and solve. D.analyze, calculate, and evaluate.

1.4 Problem Solving in Chemistry > 25 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Key Concepts The steps for solving a nonnumeric problem are analyze and solve. Effective problem solving always involves developing a plan and then implementing that plan. The steps for solving a numeric word problem are analyze, calculate, and evaluate.

1.4 Problem Solving in Chemistry > 26 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. END OF 1.4