Significant Figures. Accuracy how close of a measurement to the exact measurement

Transcription

1 Precision how exact a measurement is Significant Figures Accuracy how close of a measurement to the exact measurement Accuracy and Precision.pdf Significant Figures *all digits that are known for certainty * indicate the uncertainty of a measurement 1. All non zero digits are significant m 5 significant figures 2. All zeros between two non zero digits are significant L4 significant figures g 6 significant figures 3. Zeros to the right of a non zero digit, but to the left of the decimal point, are not significant unless specifically indicated as significant by a bar placed above the rightmost such zero that is significant. 1,000,000 g1 significant figure 200,800 km4 significant figures 200,800 km5 significant figures _ 200,800 km6 significant figures 4. All zeros to the right of a decimal point and to the left of a non zero digit are NOT significant. A lone zero to left of a decimal point is NEVER significant g 2 significant figures m 3 significant figures 5. All zeros to the right of a decimal point and to the right of a non zero digit are significant g 4 significant figures kg 4 significant figures Number S.D. Rule Practice m Practice km Practice kg Practice 4. 23,000 L Practice cm Jan 20 9:52 AM 1

2 Practice Problems , , , Feb 3 10:05 AM 2

3 Name Indicate the # of significant digits and determine which rule applies to each problem. # of S.D ,601, ,800,304,011, Jan 20 9:57 AM 3

4 Rules in calculating using Significant Figures Given that Addition and Subtraction take place in columns, round the final answer to the first column from the left containing an estimated digit. An answer cannot have more digits to the right of a decimal point than there are in the measurement with the smallest number of digits to the right of the decimal m m m m is the exact answer, to write it with the correct amount of significant figures, look at the number with the least amount of sf m So the correct answer is m m m Same thing is true when subtracting. In multiplication and division, the answer cannot be more digits than the least amount of significant digits in the problem sf x sf So the correct answer is Same thing is true when dividing. Feb 3 10:02 AM 4

5 1) grams grams = 2) 34.1 grams / 1.1 ml = 3) 2.11 x 10 3 joules / 34 seconds = 4) meters 0.11 m = 5) 349 cm cm cm = 6) 450 meters / 114 seconds = 7) kilograms kilograms = 8) 84 m/s x s = Feb 3 10:26 AM 5

6 Name Physical Science Practice Significant Digits/Figures Perform the following calculations, and express the result in the correct units and number of significant figures m 2.2 s cm X 35 cm kg 200 m m 2 X m L 180. s ml ml ml m m m kg kg kg mg mg 688 mg dl 31.2 dl 3.12 dl 11.5,487,129 m to three significant figures ml to six significant figures , cm to seven significant figures 14.A rectangle measures cm by 35.1 cm. Express its area with the proper number of significant figures. Jan 20 9:55 AM 6

7 Measurement SI : International System of Units Not IS because it is French: Le Systeme International D Unites Expressed in multiples of 10 Some things to Remember when converting any type of measures: To convert from a larger to smaller metric unit you always multiply To convert from a smaller to larger unit you always divide The latin prefixes used in the metric system literally mean the number they represent. Example: 1 kilogram = 1000 grams A kilo is 1000 of something just like a dozen is 12 of something. This is the metric conversion stair chart. You basically take a place value chart turn it sideways and expand it so it looks like stairs.the Latin prefixes literally mean the number indicated. Meter, liter or gram can be used interchangeably. Kangaroos Hop Down Mountains Drinking Chocolate Milk For every step upward on the chart you are dividing by 10 or moving the decimal one place to the left.. Example: To convert 1000 milligrams to grams you are moving upward on the stairs: Pretend you are standing on the milli gram stair tread and to get to the 1 gram stair tread you move up 3 steps dividing by 10 each time. 1000/10 = /10 = 10 10/10 = 1 or 1000/1000 = 1 or use the shortcut and just move the decimal place one place to the left with each step 1000 milligrams = 1 gram. When you move down the stairs you are multiplying by 10 for each step. So you are adding a zero to your original number and moving the decimal one place to the right with each step. Example: To convert 2 kilometers to meters you move 3 steps down on the chart so you add 3 zeros to the 2. 2 km = 2000 m Jan 19 2:28 PM 7

8 Practice Problems: 1.) 3 meters = centimeters 300 centimeters, you walked 2 steps down thereby multiplying by 100 or just add 2 zeros to the original number 2.) 40 liters = decaliters 4 decaliters, you walked up one step thereby dividing by 10, or move your decimal place one place to the left. 3.) 600 milligrams = grams 0.6 grams, you walked up 3 steps thereby dividing by 1000, or move your decimal 3 places to the left. 4.) 5 kilometers = hectometers 50 hectometers 5.) 70 centimeters = meters 6.) 900 deciliters= decaliters 7.) A pet python measured 600 cm long. How many meters long was the snake? 8.) Faith weighed 5 kilograms at birth. How many grams did she weigh? 9.) Jessica drank 4 Liters of tea today. How many deciliters did she drink? Answers meters 6. 9 decaliters 7. 6 meters long grams deciliters Jan 19 3:07 PM 8

9 Practice Problems Change to km m dam cm cm hm 4. 10,987 mg kg hm dm ml dal kg dg kl ml g hg cm km hm mm mm dam dam dm cg g hl cl Jan 19 3:08 PM 9

10 Measurement Length SI unit = meter (m) Millimeter Centimeter Mass Amount of matter in an object SI unit = kilogram (kg) Use a Balance to measure mass Measurement Pan Beams Sliding Masses Tara Knob Pointer (at Zero) Left Measuring Pan Scale Right Measuring Pan Riders Moving Masses Beams Adjustment Knob How do you use a balance? Make sure the balance is zeroed out. Put object on Pan. Move 100 g slider first. Put in notch. Move 10 g slider. Put in notch. Move 1 g slider until pointer is at zero. Add all 3 weights. Label with a "g" for grams. Volume Amount of space an object occupies SI unit = cubic Liters (L) = liquid cubic meter (m 3 ) = solid meniscus the curved upper surface of the liquid 1 ml = 1 cm 3 Density Amount of matter in a given volume D = m = g V cm 3 Weight Amount of gravitational force on an object SI = newtons (N) Spring scales used to measure weight 1 N= 100 g Temperature Measure of how fast molecules are moving SI = Kelvin (K) T F = 9 T C T C = 5(T F 32.0) 9 T K = T C Jan 20 9:47 AM 10

11 Formula's Rectangle or Square Volume = l x w x h m 3 Area = l x w m 2 Perimeter = 2(l + w) m Triangle Area = base x height m 2 2 Circle Area = πr 2 m 2 Circumference = 2πr m Sphere Volume = 4πr 3 m 3 3 Area = 4πr 2 m 2 Cylinder Volume = πr 2 h m 3 Area = 2πrh +2πr 2 m 2 Cone Volume = πr 2 h m 3 3 Area = πr 2 + πrs m 2 Pyramid Volume = base x height m 3 3 Base = area of the base Area = bh(4) + area of base m 2 2 Feb 18 8:50 AM 11

12 What is the volume and area of this cone? What is the volume and area of this pyramid? What is the volume and area of this pop can? Oct 8 9:57 AM 12

13 A = V = A = V = A = V = A = V = A = 1387 cm km 436 dam dm mg kg 543 hl ml 25 L hl Feb 25 9:58 AM 13

14 Nov 1 9:23 AM 14

15 Attachments Accuracy and Precision.pdf