Significant Figures/Dimension al Analysis

Objective: Today I will be able to: Determine the number of significant figures in a measurement Apply significant figures to solving problems Apply dimensional analysis to solving problems Informal Assessment – monitoring student questions and interactions as they complete the practice problems Formal assessment – analyzing student responses to the exit ticket and practice problems Common Core Connection Make sense of problems and persevere in solving

Lesson Sequence Evaluate: Warm-Up Explain: Significant Figures Notes Elaborate: Significant Figures Practice Elaborate: Dimensional Analysis Stations Evaluate: Exit Ticket

Warm - Up What is the difference between a qualitative and a quantitative observation? Determine whether the following statements are qualitative or quantitative The mass of a marble is 3.27g. The slime is sticky. The solution is opaque The beaker has a volume of 42 ml.

Objective Today I will be able to: Determine the number of significant figures in a measurement Apply significant figures to solving problems Apply dimensional analysis to solving problems

Homework Study for Intro to Chem Exam A – Day Friday September 13 B-Day Monday, September 16 Exam Format - 80 points 11 scientific notation questions 8 metric/ dimensional analysis problems 7 significant figures questions 16 observation/ lab safety/ equipment/ scientific notation questions Visit my website for study resources

Agenda Warm-Up Significant Figures Notes Significant Figures Practice Dimensional Analysis Stations Exit Ticket

Significant Figures

Measurements are frequently combined Uncertainty of the separate measurements must be reflected in your final answer, which is done by keeping track of the significant figures in each separate measurement

Significant Figures Certain numbers and the estimated digit of a measurement - Ex: 31.7 million has 3 sig figs – two (3 and 1) are certain, and one (7) is estimated

Atlantic Pacific Rule

If a decimal point is Present as in 52.3 km, count from the “Pacific Side” from the first nonzero digit to the end. Meaning, count from the left side of the number has 3 sig figs - How many sig figs in There are 5 sig figs (start counting at 9)

Atlantic Pacific Rule If the decimal point is Absent, as in 1530 g, count from the Atlantic Side beginning with the first nonzero digit and going to the end, counting any zero as significant. This means start from the right g has 3 sig figs How many sig figs in 190,542,100ml - There are 7 sig figs

Examples m kg ,000,000,000 mm - 2 1,908,150 L ml ns - 3

Sig Fig Calculations You cannot be more precise than your least precise measurement In multiplication and division, the measurement with the smallest number of sig digits determines how many digits are allowed in the final answer If you have several steps, carry the extra digits. Only the final answer is rounded

Examples 6.15 m x m = ? m has 3 sig figs m has 4 sig figs - Your answer can only have 3 sig figs m 2  24.8 m 2

Examples g x 45.2 g = ? g has 4 sig figs g has 3 sig figs - Your answer can only have three sig figs g  1.49 g

Final Note When doing calculations with significant figures, conversion factors do not figure in Counts and defined numbers are EXACT and have no uncertain digits Example: if you say there are 6 people in your family it is a counted number and is considered certain. There are not 6.1 people in your family Example: 12 inches = 1 foot is defined – do not use significant figures. 1 foot will never be inches. In both cases, significant figures do not apply

Significant Figures Practice Complete the practice at your desk. We will review the answers as a class

Dimensional Analysis Stations Pick 1o problems to solve. Show all work. Write answer to correct number of sig figs.Will be collected

Exit Ticket Solve and record your answer to the correct number of significant figures x 520 =.0025 x 3.15 =