MEASUREMENTS Measurements are fundamental to science Measurements may

MEASUREMENTS • Measurements are fundamental to science • Measurements may be: • a. Qualitative • b. Quantitative

MEASUREMENTS • Qualitative Measurement: is a nonnumerical measurement • Example: The solution turned brown when ammonia was added to iron (III) chloride

QUANTITATIVE MEASUREMENTS • Quantitative Measurements: consist of two parts • a. A number • b. A scale (or unit) • Example: • The rock has a mass of 9. 0 kg

SI UNITS AND PREFIXES • • • The SI system used prefixes “Kilo-” means 1000; symbol is k “Hecto” means 100; symbol is h “Deca” mean 10; symbol is da “Base” means 1; meter/liter/gram “Deci-” means 0. 1; symbol is d “Centi-” means 0. 01; symbol is c “Milli-” means 0. 001; symbol is m King Henry Died By Drinking Chocolate Milk

LENGTH • Length- is the distance between two points • The SI unit of length is the meter (m) • Devices used to measure length: • Rulers, Tape Measurers, and Meter Sticks

VOLUME (V) • Volume- is the amount of space an object occupies • Volume of a cube is length * width * height • Volume of a cylinder is V=πr 2 h • The SI unit for volume is m 3(meter cubed) • Other units for V: m. L, cm 3, dm 3 • The Liter (L) is also used for volume of liquids

VOLUME CONTINUED • Conversions for volume: • 1 dm 3 (decimeter cubed ) = 1 L • 1 cm 3 = 1 m. L (milliliter)= 1 cc • Devices Used to Measure Volume: • Ruler, Graduated Cylinder, Beaker

MASS • Mass-is the amount of matter that an object contains • SI Unit for Mass is measured in kilograms (kg) • Grams (g) are also used but are very small

TIME • Time- is the interval between two events • Unit of time is the second

TEMPERATURE • Temperature- is the measure of the average kinetic energy of particles • Temperature is measured in Kelvin (K) in the SI system • K = 273 + °C • ˚C= K- 273 • Temperature is usually given in °C

CONVERT THE FOLLOWING TEMPERATURES • 1. • 2. • 3. • 4. 36 °C to K 50 K to °C 105 K to °C -236 °C to K

TERMS USED FOR MEASUREMENTS • In comparing scientific results, the following terms are applied: • a. accuracy • b. precision

ACCURACY • Accuracy refers to the agreement of one experimental result to the true or accepted value • The closer the value is to the true value, the more accurate one is

ACCURACY • Examples of accuracy: • kicking a soccer goal • hitting a three point shot • determining the value of to be 3. 13

PRACTICE: TELL IF THE ACCURACY IS GOOD OR POOR • a. Finding the percent H 2 O 2 to be 2. 9% (the bottle says it contains 3%) • b. Finding that a 2 Liter bottle only contains 1. 5 Liters of soda • c. Filling a 1000 m. L volumetric flask with 1050 m. L of water

PRECISION • Precision refers to how close several different experimental values are to each other

PRECISION • Examples: • scoring three goals in a soccer game • Shooting an air ball five times • finding the value for to be 3. 12, 3. 15, 3. 13

PRECISION AND ACCURACY PROBLEMS • Precision problems usually arise from the skill of the person doing the experiment or the division of the measuring instruments • Accuracy problems usually related to the quality of the equipment used to make measurements

DESCRIBE THE ACCURACY AND PRECISION OF THE FOLLOWING AS EITHER GOOD OR POOR • A student makes the following grades: • a. 99, 100, 98, 100 • b. 45, 43, 44, 42 • c. 100, 23, 60, 89