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Basic Math Concepts needed for Chemistry. The Factor Label Method. Learning Goals. Success Criteria. Prerequisite Skills and Materials. Skills/concepts you need to learn/have prior to learning this concept: Significant digits Scientific notation Using scientific units
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Basic Math Concepts needed for Chemistry The Factor Label Method
Prerequisite Skills and Materials • Skills/concepts you need to learn/have prior to learning this concept: • Significant digits • Scientific notation • Using scientific units • Materials you need to have prior in order to complete questions using this method: • Scientific calculator • Periodic Table (when doing stoichiometry)
Value of the factor Label method • The factor-label method is a logical and consistent way of converting a quantity in one unit into the equivalent quantity in another unit • The factor label method allows students to: • complete multi-step questions in one step! • keep track of units more easily • Keep track of significant digits easily
Sample Question Example: Determine how many seconds are in 3.52 minutes • Step 1: Identify Key Value and Conversion Factor Equation 3.52 minutes (key value) 1 minute = 60 seconds (conversion factor equation or equality) • Step 2: Identify Required Value The required value is number of seconds in 3.52 minutes. • Step 3: List Possible Conversion Factors Using the conversion factor equation (equality), the possible conversion factors are • OR
Sample Question • These fractions are equal to 1 because, in both cases, the numerators and denominators are of equal value: 60 s is the same length of time as 1 min, and vice versa. All conversion factors equal 1. • The only difference is that one fraction is inverted when compared to the other fraction. • The conversion factor you use in the solution to a problem depends on the units of the given value. Choose the form of the conversion factor whose denominator has the same units as the given value. Since multiplying by a conversion factor is like multiplying by 1, only the units change.
Sample Question • Step 4: Substitute Values into Solution Equation, and Solve required value = seconds = = 211.1 s (calculator) = 211 s (applying significant digit rules – 3.52 min has 3 significant digits, so the answer must have 3 significant digits) *complete the whole calculation then apply significant digits
Practice Question #1: • Multi-step equation • Practice 2: Convert 34695 mm into kilometres. • Conversion factors: 1000mm = 1 m 1000m = 1km Want km Place the value in mm into the denominator because it cancels the mm unit in the denominator Place the value in m into the denominator to cancel the m in the denominator
Practice Question #2: • Practice 1: Convert 38 cm into feet. What are the conversion factors?
Practice Question #3: • Convert 25.6 m/s into km/h?
Practice Question #4 • If Gasp cigarettes have 5 mg tar and 0.4 mg nicotine per cigarette and there are 20 cigarettes per pack, how many packs of cigarettes would have to be smoked to coat your lungs with 4 oz (1/4 lb.) of tar? How many packs would you have to smoke to introduce your lungs to one gram of the drug nicotine?