2 Significant figures (sig figs) How many numbers mean somethingWhen we measure something, we can (and do) always estimate between the smallest marks.21345
3 Significant figures (sig figs) The better marks the better we can estimate.Scientist always understand that the last number recorded is actually an estimate12345
4 Which numbers count?All nonzero numbers in a recorded measurement are significantZeros between nonzeros are significant12004Zeros in front of nonzeros are NOT significant0.045
5 Which numbers count?zeros at the end of a number after the decimal point are significantZeros after the number but no decimal are NOT significant458300
6 Sig Figs Only measurements have sig figs. Counted numbers are exact A dozen is exactly 12There are 2405 students in this schoolBeing able to locate, and count significant figures is an important skill.Quantitative!
7 Sig FigsHow many sig figs in the following measurements?458 g4085 g4850 gggg
9 Problems 50 is only 1 significant figure if it really has two numbers, then how can I write it?Scientific notation5.0 x 101now the zero counts.
10 Adding and subtracting with sig figs Line up the decimalsAdd or subtractCut off the answer based on the least significant measurement givenRound up if necessary
11 For example27.936.4+First line up the decimal places27.936.4+27.936.4Then do the addingFind the estimated numbers in the problem34.33This answer must be rounded to the tenths place
12 Rounding ruleslook at the number to the right of the one you’re rounding.If it is 0 to 4, don’t change itIf it is 5 to 9, make it one biggerround to four sig figsto three sig figsto two sig figsto one sig fig
17 Measuring The numbers are only HALF of a measurement “It is 10 long” 10 what?Numbers without units are meaningless!
18 The Metric System 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.prefix tells you how many times to divide or multiply by 10.
19 Base Units Length - meter more than a yard - m Mass - grams - about a raisin - gTime - second - sTemperature - Kelvin or ºCelsius K or CEnergy – Joules - JVolume - Liter - half a two liter bottle- LAmount of substance - mole - mol
20 Prefixes kilo k 1000 deci d 1/10 centi c 1/100 milli m 1/1000 kilometer - about 0.6 milescentimeter - less than half an inchmillimeter - a paperclip wire
21 k h D d c m Converting in Metric 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.
22 k h D d c m Conversions convert 25 mg to grams convert 0.45 km to mm convert 35 mL to litersIt works because the math works, we are dividing or multiplying by 10 the correct number of times
23 Converting from metric to standard Requires conversion factorsUse dimensional analysisUnits must work out in the final answer
24 Dimensional AnalysisA ruler is 12.0 inches long. How long is it in cm? ( 1 inch is 2.54 cm)in meters?A race is 10.0 km long. How far is this in miles?1 mile = 5280ft1 meter = ftPikes peak is 14,110 ft above sea level. What is this in meters?