Chemistry Chapter 3: Scientific Measurement Mrs. Wanstreet

Two Types of Measurements Qualitative Measurements: –Give results in a descriptive, non-numerical form –What are some examples of qualitative measurements in your daily life? Quantitative Measurements Qualitative Measurements: –Give results in a descriptive, non-numerical form –What are some examples of qualitative measurements in your daily life? Quantitative Measurements

Use the picture I’m about to show you and make some qualitative measurements or observations about it!

Quantitative Measurements Quantitative Measurements: give results in a definite form, usually as numbers and units. –Ex: Taking the temperature of a substance using a thermometer. –Requires a measuring instrument. Quantitative Measurements: give results in a definite form, usually as numbers and units. –Ex: Taking the temperature of a substance using a thermometer. –Requires a measuring instrument.

Scientific Notation A number is written as a product of two numbers, a coefficient and 10 raised to a power. –Ex: 3.4x10 4 –Ex: 5.2x10 -3 A number is written as a product of two numbers, a coefficient and 10 raised to a power. –Ex: 3.4x10 4 –Ex: 5.2x10 -3

N x 10 n N is a number between 1 and … n is a positive or negative integer Scientific Notation

The number of atoms in 12 g (grams) of carbon is: –602,200,000,000,000,000,000,000 –Scientific notation: x LARGE NUMBER = Positive Exponent (LIP) The number of atoms in 12 g (grams) of carbon is: –602,200,000,000,000,000,000,000 –Scientific notation: x LARGE NUMBER = Positive Exponent (LIP)

Scientific Notation T he mass of a single carbon atom in grams is: – –Scientific notation: 1.99 x SMALL NUMBER = Negative Exponent (RING) T he mass of a single carbon atom in grams is: – –Scientific notation: 1.99 x SMALL NUMBER = Negative Exponent (RING)

Scientific Notation Think of the number 185: –185 = 1.85 x 100 –100 = 10 x 10 = 10 2 –185 = 1.85 x 10 2 (in scientific notation) Now think of the number 1800: –1800 = 1.8 x 1000 –1000 = 10 x 10 x 10 = 10 3 –1800 = 1.8 x 10 3 (in scientific notation) Think of the number 185: –185 = 1.85 x 100 –100 = 10 x 10 = 10 2 –185 = 1.85 x 10 2 (in scientific notation) Now think of the number 1800: –1800 = 1.8 x 1000 –1000 = 10 x 10 x 10 = 10 3 –1800 = 1.8 x 10 3 (in scientific notation)

“LIP RING” Large is PositiveSmall is Negative Left is PositiveRight is Negative (G’s) Large is PositiveSmall is Negative Left is PositiveRight is Negative (G’s)

x x x x x x10-4 Try These!!

Accuracy : how close a measurement is to the true value Precision : how close a set of measurements are to each other accurate & precise but not accurate & not precise Suppose the true value is 100. Which diagram is precise? Accurate? A. B. C. A. B. C.

Percent Error Calculation used to evaluate the accuracy of a measurement. An experimental value is compared to an accepted value to evaluate how close the experiment is to the true result. Calculation used to evaluate the accuracy of a measurement. An experimental value is compared to an accepted value to evaluate how close the experiment is to the true result.

Percent Error % error = │exp value – acc value│ acc value –Ex.: Using a thermometer you take the temperature of your cat. The normal value of the cat’s temperature is 100°C and your reading was 99.1°C. What is the percent error of the thermometer? % error = │exp value – acc value│ acc value –Ex.: Using a thermometer you take the temperature of your cat. The normal value of the cat’s temperature is 100°C and your reading was 99.1°C. What is the percent error of the thermometer? x 100

Calculate: % error = │exp value – acc value)│% error = │exp value – acc value)│ acc value │99.1°C – 100.0°C│ / 100.0°C x 100%│99.1°C – 100.0°C│ / 100.0°C x 100% 0.9 / x 100%0.9 / x 100% x 100%0.009 x 100% 0.9%0.9% % error = │exp value – acc value)│% error = │exp value – acc value)│ acc value │99.1°C – 100.0°C│ / 100.0°C x 100%│99.1°C – 100.0°C│ / 100.0°C x 100% 0.9 / x 100%0.9 / x 100% x 100%0.009 x 100% 0.9%0.9% x 100

Significant Figures: The Rules Every nonzero digit in a reported measurement is assumed to be significant. Zeros appearing between nonzero digits are significant. Leftmost zeros appearing in front of nonzero digits are NOT significant. Ex.: Trailing zeros, or zeros to the right of the number, are significant ONLY if the number is written with a decimal point. Every nonzero digit in a reported measurement is assumed to be significant. Zeros appearing between nonzero digits are significant. Leftmost zeros appearing in front of nonzero digits are NOT significant. Ex.: Trailing zeros, or zeros to the right of the number, are significant ONLY if the number is written with a decimal point.

How many significant figures?

In groups, determine the number of significant figures… 1) ) )7.09 x 10 ¯5 4)91,600 5) ) ) )7.09 x 10 ¯5 4)91,600 5) )3.200 x )250 8)780,000,000 9) )

Answers! 1)5 2)3 3)3 4)3 5)4 1)5 2)3 3)3 4)3 5)4 6)4 7)2 8)2 9)3 10)3

Units Units: part of a measurement that tells what scale or standard is being used. The system of units used in science is the SI system which is based on the metric system. Units: part of a measurement that tells what scale or standard is being used. The system of units used in science is the SI system which is based on the metric system.

SI Base Units Mass Kilogram (kg) Length Meter (m) Time Second (s) Temperature Kelvin (K) Study Table 3.1 on page 63!!

Metric System Prefixes * Memorize chart on pg. 64*

Amount of matter present in a given volume Base SI Unit = kg/m 3 In chemistry, we usually use: g/cm 3 Amount of matter present in a given volume Base SI Unit = kg/m 3 In chemistry, we usually use: g/cm 3 density = massvolume d =d =d =d =mV Density m = d x V V =V =V =V =md

Specific Gravity Comparison of the density of a substance with the density of a reference substance, usually at the same temperature. SG= density of substance density of water Comparison of the density of a substance with the density of a reference substance, usually at the same temperature. SG= density of substance density of water

Temperature determines the direction of heat transfer Celsius: 0 o C to 100 o C Kelvin: K (freezing point of water) to K (boiling point of water) also 0K (absolute zero) K= o C o C = K Temperature determines the direction of heat transfer Celsius: 0 o C to 100 o C Kelvin: K (freezing point of water) to K (boiling point of water) also 0K (absolute zero) K= o C o C = K Temperature