Presentation on theme: "Matter and Measurement"— Presentation transcript:
1Matter and Measurement Chapter 1Matter and Measurement
2Classification of Matter Check your neighbors understanding for the following words and organize them into a flow chart:Pure SubstanceMixtureMatterHomogeneousHeterogeneousElements/Compounds
3Practice Problem“White Gold,” used in jewelry, contains two elements, gold and palladium. Two different samples of white gold differ in the relative amounts of gold and palladium that they contain. Both are uniform in composition throughout. Without knowing any more about the materials, classify white gold. Be able to defend your answer.
4Practice ProblemAspirin is composed of 60% Carbon, 4.5% Hydrogen, and 35.5% oxygen by mass, regardless of its source. Classify aspirin. Defend your answer.Bonus! Empirical Formula?
11Uncertainty in Measurement Precision vs. Accuracy?Significant Figures1) All nonzero digits are significant:1.234 g has 4 significant figures1.2 g has 2 significant figures.
12(2) Zeroes between nonzero digits are significant: 1002 kg has 4 significant figures,3.07 mL has 3 significant figures.
133) Leading zeros to the left of the first nonzero digits are not significant; such zeroes merely indicate the position of the decimal point:0.001 oC has only 1 significant figure, g has 2 significant figures
14Trailing zeroes that are also to the right of a decimal point in a number are significant: mL has 3 significant figures, 0.20 g has 2 significant figures.
15When a number ends in zeroes that are not to the right of a decimal point, the zeroes are not necessarily significant:190 miles may be 2 or 3 significant figures, 50,600 calories may be 3, 4, or 5 significant figures. The potential ambiguity in the last rule can be avoided by the use of standard exponential, or "scientific," notation. For example, depending on whether the number of significant figures is 3, 4, or 5, we would write 50,600 calories as:5.06 × 104 calories (3 significant figures) × 104 calories (4 significant figures), or × 104 calories (5 significant figures).In other words
16Sig Figs in Calculations (1) In addition and subtraction, the result is rounded off to the last common digit occurring furthest to the right in all components. Another way to state this rules, it that, in addition and subtraction, the result is rounded off so that it has the same number of decimal places as the measurement having the fewest decimal places. For example,100 (assume 3 significant figures) (5 significant figures) = , which should be rounded to 124 (3 significant figures).
17In multiplication and division, the result should be rounded off so as to have the same number of significant figures as in the component with the least number of significant figures. For example,3.0 (2 significant figures ) × (4 significant figures) = which should be rounded off to 38 (2 significant figures).In other words
18Try this…In a long calculation involving mixed operations, carry as many digits as possible through the entire set of calculations and then round the final result appropriately. For example,(5.00 / 1.235) (6.35 / 4.0)= =
19Thus, the correct rounded final result should be 8.6. Practice Sheet
20Conversion FactorsIt is important to know how to use conversion factors.I will also call it dimensional analysis.Get used to doing it so that AP graders can follow what you are doing!How can you convert miles to kilometers?How can you convert a quartof something to liters andreverse?
22Lets take the first miles to kilometers. It I had to travel 75.4 miles, how many kilometers did I travel?From the conversion chart we know 1 mile = kilometersNow set it up as a conversion factor (a fraction)1.609 kilometers then multiply it by how many miles1 mile75.4 miles(1.609 kilometers)== 121 kilometers (notice the 3 sig. fig.’s)
23The second question was how many liters are there in a quart The second question was how many liters are there in a quart? Lets find out how many liters are in quarts.Again look up any conversion factors that you may have.We are in luck the chart says 1 L = quartMake the factor label needed.1 Liters1.057 quartStart with what you are given and use the fraction.1.000 quarts/ 1 liter =/ quarts= litersNotice the four sig. fig.’s!