2 By the end of this lesson you should be able to: Distinguish between exact and measured numbers.Identify different pieces of lab equipment, what it measures & the units of measurementState the SI units for mass, length, volume, temperature, and amount of a substance.Use a ruler, graduated cylinder, triple beam balance to make accurate measurement (to correct place value)
3 By the end of this lesson you should be able to: Explain how a measured number tells the audience about the accuracy of the tool used to make a measurementDetermine the number of significant figures in a given numberPerform calculations & express solutions with correct number of significant figures
5 Exact Numbers (3 types)Counting objects are always exact 2 soccer balls 4 pizzasExact relationships such as conversion factors 1 foot = 12 inches 1 meter = 100 cmConstants/ By Definition Pi, Avogadro’s #, speed of light
6 Measured NumbersMeasured numbers will always include some degree of ERRORAn instrument is used for measuring and therefore the user must at some point estimate the value.When you use your calculator to calculate using a measured number your answer can only be as accurate as your worst measurement.
7 Learning CheckA. Exact numbers are obtained by 1. using a measuring tool 2. counting 3. definition B. Measured numbers are obtained by
8 Learning Check Classify each of the following as an exact or a measured number.1 yard = 3 feetThe diameter of a red blood cell is 6 x 10-4 cm.There are 6 hats on the shelf.Gold melts at 1064°C.
9 Metric System Every measurement has 2 parts: NumberUnit (scale)SI System (le Systeme International) is based on the metric systemPrefix + Base UnitPrefix tells you the power of 10 to multiply by (easy for conversions)
10 SI Units Measuring Base Unit Symbol Mass Kilogram kg Volume (solid) (liquid)Cubic centimeterLitercm3LLengthMetermTimeSecondsTemperatureKelvinKAmount of SubstanceMolesmolForceNewtonN
11 Important Prefixes Prefix Symbol Amount Scientific Notation Giga - G 1,000,000,000109Mega -M1,000,000106Kilo -k1,000103Decid0.110-1Centi -c0.0110-2Milli -m0.00110-3Micro -10-6Nano-n10-9
13 Tool: Ruler Measures length Measures in centimeter (cm) All measurements have a degree of uncertainty!We can see the markings between cmWe can’t see the markings between theWe must “guess” between 0.6 & 0.7We record 1.67 cm as our measurementThe last digit an 7 was our guess...stop there
14 What is the measure? What is the length of the wooden stick? 1) 4.5 cm
27 Significant FiguresNumbers that are important for performing calculations to ensure that your final answers are accurateThere are many significant figure rules
28 THE RULES All non-zero numbers are significant Examples: 65.23 23,456 4 sig. figs.23,4565 sig. figs.7 sig. figs
29 THE RULES All zeros between two non-zero numbers are significant Examples:20144 sig. figs300,0026 sig. figs1.00055 sig. figs.
30 THE RULES Place holder zeros are NOT significant Leading zero - before any digits0.00122 sig. figsTrailing zeros – after digits but BEFORE a decimal345,0003 sig. figs41,980,000.4 sig. figs
31 THE RULESAll zeros at the end of a number and AFTER the decimal point are significantExamples:5.00005 sig figs402.04 sig figs0.4503 sig figs
32 THE RULES Significance of a DECIMAL point MUST PAY ATTENTION Try some more as Mrs. Page puts them on the board.QUESTION???? ASK NOW!!!!
33 Calculations w/ Sig. Figs. RULE 1. In carrying out a multiplication or division, the answer cannot have more significant figures than either of the original numbers. (answer has # of sig. figs of smaller # of sig figs)
34 Calculations w/ Sig. Figs. RULE 2. In carrying out an addition or subtraction, the answer cannot have more digits after the decimal point than either of the original numbers.