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Problem Solving in Chemistry. Chapter 4. What do I do now?. List several useful problem solving skills Deductive reasoning Inductive reasoning A three step problem solving approach, (ACE) Analyze Calculate Evaluate. Simple Conversion Problems. Conversion Factors
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Problem Solving in Chemistry Chapter 4
What do I do now? • List several useful problem solving skills • Deductive reasoning • Inductive reasoning • A three step problem solving approach, (ACE) • Analyze • Calculate • Evaluate
Simple Conversion Problems • Conversion Factors • Must be constructed from equivalent measurements • Example: 1 dollar equals 4 quarters, ($1 = 4 x 25 cents) • Equal in value • Example: 1meter = 100centimeters • A small number of large items = a large number of small items • The meter stick has 100 cm or 1000 millimeters or 10 decimeters • All are valid and equivalent measurements • 100cm/1meter converts from meters to cm • 1 meter/100 cm converts from cm to meters
Simple Conversion Problems • Dimensional Analysis is a way to analyze and solve problems using the UNITS or dimensions of the measurements • If each person at a party will eat 2 hamburgers, how many will you need for 18 people? 36 HB • 2 HB/1 person x 18 person = 36 HB • If each HB has 2 pickles, how many will you need? • 36 HB x 2 pickles/1 HB = 72 pickles • If 1 jar of pickles has 110 pieces, how many HB could be made?
More Complex Problems • Multi Step Problems • Miles to Feet to Yards: If you went 3.5 miles, how many yards is that? • What you need to know: • 1 mile = 5280 feet • 1 yard = 3 feet • How to convert, (the units miles and feet cancel) • 3.5 miles x 5280 feet/1mile x 1yard/3 feet = ___ yards • You get an answer in yards -> 6160 yards
More Complex Problems • Converting Complex Units • Many measurements are expressed as a ratio of units, (miles per hour, Kilometers per second,…) • Convert 10 mi/hr to km/sec, (the units of same color cancel) • 10 mi/hr x 1 km/.55 mi x 1 hr /60 min x 1min / 60 sec= So you are left with units of km/sec The math is 10 x 1 x 1 x 1 / .55 x 60 x 60 = The answer is 0.005 km/sec