2 2 Types of Measurements QuantitativeQualitative Measurement based on words. Ex: Tall building cold air Measurement based on numbers. Ex: 10.5 grams 4.65 mL

2 “The pencil is 3 inches.” This is an example of an accurate measurement.

2 “The pencil is 3.0 inches.” This is an example of an accurate and more precise measurement.

2 “The pencil is 4 inches.” This is an example of a measurement that is not accurate and not precise.

2 Which ruler below would produce a more precise measurement? a. b. c. The greater number of divisions on ruler “c” allow for a more precise (and hopefully accurate) measurement. Being more precise, measurements made with this ruler will contain more significant figures.

2 Rules for Determining the Number Of Significant Figures RULE All nonzero numbers are significant in a measurement. Ex: 4250 g has three “sig figs”. Return

2 Rules for Determining the Number Of Significant Figures Zero(s) between two sig figs are significant. Ex: 3006 mL has four “sig figs”. RULE 2 Return

2 Rules for Determining the Number Of Significant Figures Final zero(s) after the decimal are significant. Ex: grams has four “sig figs”. RULE 3 Return

2 Rules for Determining the Number Of Significant Figures Zero(s) that “trail” sig figs before a decimal are significant…but ONLY if the decimal is visible. Ex: 4250 g has 3 sig figs….BUT g has 4 sig figs. RULE 4 Return

2 But what about numbers written in scientific notation? M x 10 n Here, the number of sig figs is determined by the base number, M. Example: x 10 5 m has four sig figs.

2 Measurement Number of “Sig Figs” Rule(s) 20 x10 3 grams 205 grams grams 20. grams Rule(s): 1 and 4 Rule(s): 1 and 2 Rule(s): 1, 2,and 3 Rule(s): 1 and 4 Click on a Rule “link” to review: Rule 1 Rule 2 Rule 3 Rule 4Rule 1Rule 2Rule 3Rule 4

2 Measurement Number of “Sig Figs” Rule(s) 70 grams 70. grams 70.0 grams grams Rule(s): 1 Rule(s): 1 and 4 Rule(s): 1, 2, and 3 Rule(s): 1 and 2 Click on a Rule “link” to review: Rule 1 Rule 2 Rule 3 Rule 4Rule 1Rule 2Rule 3Rule 4

2 So why do we have to know all this information and all these rules? Answer “So we will know how many digits to put in our answers when we perform mathematical operations”.

2 Mathematical Operation “Your focus should be on…” Reason When adding or subtracting values, your answer must be as precise as the least precise number in your calculation. When multiplying or dividing values, your answer must contain the same number of “sig figs” as the least significant number in your calculation. Example: 6.1 m m = _______ m 8.4 Notice that our answer is carried out to the nearest tenth…just like the least precise number in our calculation!

2 Mathematical Operation “Your focus should be on…” Reason When adding or subtracting two values, your answer must be as precise as the least precise number in your calculation. When multiplying or dividing values, your answer must contain the same number of “sig figs” as the least significant number in your calculation. Example: 6.00 m x 2.0 m = _______ m 2 12 Notice that our answer has two “sig figs”…just like the least significant number in our calculation! Mathematical Operation “Your focus should be on…” Reason For additional practice, complete the worksheet provided by your teacher.

2 The standards of the measurement used by scientist are those of the metric system. The metric system is based on the number 10 or multiples of The metric system Is established in France 2013 Metric System Timeline The SI System Is adopted SI Base Units of Measurement Quantity MeasuredUnitSI Symbol Length meter m Mass kilogram kg Temperature kelvin K Amount of a mole mol substance Length is the distance between two points. Mass is a measure of the amount of matter in a substance. Temperature is a measure of the average kinetic energy of the particles in a substance. A mole represents the amount of a substance.

2 Prefixes in Use for the metric system PrefixSymbolMeaning kilok-1000 x larger decid- 10 x smaller centic- 100 x smaller milli m x smaller When metric prefixes are attached to units of measurement, we gain an idea of the magnitude (size) of the measurement. Ex: 1000 g = 1 kg When metric prefixes are attached to units of measurement, we gain an idea of the magnitude (size) of the measurement. Ex: 1000 g = 1 kg

2 1 cm 10 cm = 1 dm 1 liter = 1 dm 3 = 1000 cm 3 = 1000 mL 10 cm = 1 dm Volume = length x width x height

2 Density = mass / Volume Substance Mass (g) Volume (cm 3 ) Density (g/cm 3 ) Wood Water10 1 Lead

2 Substance Density (g/cm 3 ) Gold19.3 Mercury13.5 Lead11.4 Iron7.87 Aluminum2.70 Water0.997 Water (4 o C)1.00 Ice (0 o C)0.917 Air (dry)