Measuring The numbers are only half of a measurement How wide is the room? It is 10. 10 what? Numbers without units are meaningless.
What are units anyways? A unit is a particular physical quantity, defined and adopted by convention, with which other particular quantities of the same kind are compared to express their value.
The system we use How many ounces in a cup? –8–8 How many ounces in a pound? – 16 How many feet in a yard? –3–3 How many feet in a mile? – 5,280
The SI System Le Système International d’Unités Easier to use because it is a decimal system Every conversion is by some power of 10. A metric unit has two parts: a prefix and a base unit. A prefix tells you how many times to divide or multiply by 10.
Base Units Mass - gram (g) Length – meter (m) Temperature - kelvin (K) » - Celsius (C) Time - second (s) Derived Units Area – square meter (m 2 ) – length x width Volume – cubic meter (m 3 ) – length x width x height
Prefixes Prefixes always mean the same thing! Kilo- 1,000 Hecto- 100 Deka- 10 ***Base = 1*** Deci- 0.1 or 1/10 Centi- 0.01 or 1/100 Milli- 0.001 or 1/1000
Converting khDdcm how far you have to move on this chart, tells you how far, and which direction to move the decimal place. The box is the base unit, meters, Liters, grams, etc.
Conversions Change 5.6 m to millimeters khDdcm l starts at the base unit and move three to the right. l move the decimal point three to the right 5600
Metric system 1 km = 1000 m 1 dm = 0.1 m 1 cm = 0.01 m 1 mm = 0.001 m 1 m = 10 -6 m 1 nm = 10 -9 m 1 kg = 1000 g 1 dg = 0.1 g 1 cg = 0.01 g 1 mg = 0.001 g 1 g = 10 -6 g 1 ng= 10 -9 g
Measuring Temperature Celsius scale water freezes at 0ºC water boils at 100ºC body temperature 37ºC room temperature 20ºC - 25ºC
Measuring Temperature Kelvin is always bigger C = K -273 K = C + 273 Kelvin starts at absolute zero (-273 ºC) Kelvin can NEVER be negative! ! ! ! ! ! ! ! ! ! ! !
Measuring Temperature Fahrenheit is always bigger F = C (9/5) + 32
Volume – a derived unit Volume is the amount of space an object occupies Calculated by multiplying L x W x H It is also possible to find the volume of an object by measuring the volume of water that it displaces 1 mL = 1 cm 3
Types of measurement Quantitative - objective; most people would get nearly the same answer - use numbers to describe – 4 feet – 100ºF Qualitative - subjective; personal opinion may influence answer - use description without numbers – extra large – hot
Scientists prefer: Quantitative - easy check Easy to agree upon, no personal bias BUT, the measuring instrument limits how good the measurement is.