Significant Figures Used to communicate the accuracy of measurements

When is a digit significant? The digits 1 through 9 are always significant Zeros may or may not be significant

How do I determine significant figures We will use a method called Atlantic- Pacific to determine the number of significant figures.

Using Atlantic-Pacific Method Is there a decimal? No: count from the Atlantic side of the number starting with first non-zero number 2300 How many significant figures in 2300? 2

More Practice How many significant figures in

Using Atlantic-Pacific Method Is there a decimal? Yes: count from the Pacific side of the number starting with first non-zero number How many significant figures in ? 3

More Practice How many significant figures in

Assignment Complete page 2 of Math Guided Practice.

Math Guided Practice p , ,000, x x x

Scientific Notation Move decimal point so there is one non- zero digit to the left of the decimal point. Remember to include only significant figures when you rewrite number with a decimal place. Count the number of places the decimal point was moved. This becomes the power for the 10 x. Since is greater than 1 the power will be positive x 10 x x 10 6

Scientific Notation used to make both really big and small numbers easier to work with. Numbers greater than one will have positive exponent Numbers less than one will have negative exponent Preserve the number of significant figures

Scientific Notation Practice

Scientific Notation Practice

Scientific Notation to Standard Notation x 10 5 = x =

Math Guided Practice p.1 1) __________ 2) __________ 3) __________ 4) __________ 5) __________ 6) __________ 7) __________ 8) __________ 9) __________ 10) __________

Math Guided Practice p.1 11) 1 x 10 8 __________ 12) 2.05 x 10 4 __________ 13) 3 x __________ 14) 8.76 x __________ 15) 6.34 x __________ 16) 2.00 x __________ 17) 7.11 x __________ 18) 3 x 10 1 __________ 19) 3 x __________ 20) 3 x 10 3 __________

Entering Scientific Notation in a Calculator 1. Type in the number 2. Press the EE or EXP key 3. Type in the exponent. Remember to add the “-” if the exponent is negative. Use the EE or EXP key only!

Mathematical Operation with Significant Figures p. 3 Math Guided Practice An answer cannot be more precise than the least precise measurement in the operation

Addition and Subtraction with Significant Figures When adding or subtracting numbers, count the NUMBER OF DECIMAL PLACES to determine the number of significant figures. The answer cannot CONTAIN MORE PLACES AFTER THE DECIMAL POINT THAN THE SMALLEST NUMBER OF DECIMAL PLACES in the numbers being added or subtracted = 6.5

Addition and Subtraction with Significant Figures = = = 3.62 – 1.6 =

Multiplication and Division with Significant Figures When multiplying or dividing numbers, count the NUMBER OF SIGNIFICANT FIGURES for each number. The answer must be rounded to the smallest number of significant figures. 3.2 x 1.21 x =

Multiplication and Division with Significant Figures 1.58 x = 12.6 / 6 = (1.20 x 10 3 ) (4.369 x 10 2 ) = (6.72 x ) / (5.2 x ) =

MSDS Material Safety Data Sheet lRzB8xTM3w

MSDS Complete CH-1b MSDS Scavenger Hunt using the MSDS documents on your table.

NFPA Labels NFPA Labels TPY14maDbw

Taking Measurements When taking measurements: Read to the smallest mark on the instrument Estimate one digit past the smallest mark

Measuring Volume  Determine the volume contained in a graduated cylinder by reading the bottom of the meniscus at eye level.  Read the volume using all certain digits and one uncertain digit.  Certain digits are determined from the calibration marks on the cylinder.  The uncertain digit (the last digit of the reading) is estimated.

Reading the Graduated Cylinder Liquids in glass and some plastic containers curve at the edges Changing the diameter of the cylinder will change the shape of the curve This curve is called the MENISCUS

Your eye should be level with the top of the liquid Reading the Graduated Cylinder You should read to the bottom of the MENISCUS

Use the graduations to find all certain digits There are two unlabeled graduations below the meniscus, and each graduation represents 1 mL, so the certain digits of the reading are… 52 mL 52 mL.

Estimate the uncertain digit and take a reading The meniscus is about eight tenths of the way to the next graduation, so the final digit in the reading is. The volume in the graduated cylinder is 0.8 mL 52.8 mL.

10 mL Graduated Cylinder What is the volume of liquid in the graduate? 6.62mL

25mL graduated cylinder What is the volume of liquid in the graduate? 11.5 mL

100mL graduated cylinder What is the volume of liquid in the graduate? 52.7mL

What is this reading? Practice Reading the Graduated Cylinder 61.2 ml

What is this reading? Practice Reading the Graduated Cylinder 42.9 ml

Measuring Liquid Volume Images created at What is the volume of water in each cylinder? Pay attention to the scales for each cylinder.

Reading a graduated cylinder All of the equipment below measures volume in mL but the scales for each are different. 16.5mL 3.80mL 7.5mL

What is the volume in the buret?

The Thermometer o Determine the temperature by reading the scale on the thermometer at eye level. o Read the temperature by using all certain digits and one uncertain digit. Certain o Certain digits are determined from the calibration marks on the thermometer. uncertain o The uncertain digit (the last digit of the reading) is estimated. o On most thermometers encountered in a general chemistry lab, the tenths place is the uncertain digit.

Do not allow the tip to touch the walls or the bottom of the flask. If the thermometer bulb touches the flask, the temperature of the glass will be measured instead of the temperature of the solution. Readings may be incorrect, particularly if the flask is on a hotplate or in an ice bath.

Reading the Thermometer Determine the readings as shown below on Celsius thermometers: _ _. _  C

Measuring Solid Volume Click here for an online activity about volumeClick here for an online activity about volume. Choose Lessons  Volume & Displacement 10 cm 9 cm 8 cm We can measure the volume of regular object using the formula length x width x height. _____ X _____ X _____ = _____ bus/unit14/new/testingmain1.htm We can measure the volume of irregular object using water displacement. Amount of H 2 O with object = ______ About of H 2 O without object = ______ Difference = Volume = ______

What is this volume? Practice Reading the Graduated Cylinder 47.0 ml

Online Practice Reading a graduated cylinder a_meniscus.swf a_meniscus.swf Reading a buret wf wf Reading a ruler a_ruler.swf a_ruler.swf

Homework Complete p. 3 in Math Guided Practice Complete Measuring Practice Separation Techniques Practice

Experiments Dependent Variable(s) ◦ This is the response that you are measuring Independent Variable(s) ◦ These are the ones you are controlling or manipulating

Experiments Control ◦ This is what you use as a comparison. Constants ◦ Constants do not change throughout the experiment.

Experiments Example: A student is determining the rate at which a certain substance evaporates by checking the volume every 60 minutes. I.V. = time (minutes) D.V. = volume

Experiments Example: A balloon full of air is heated slowly to observe its change in volume. I.V. = temperature D.V. = volume

What is the I.V., D.V. and Control? Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks.

Observations Qualitative ◦ Descriptive data such as color, texture, relative size, or shape. Quantitative ◦ Numberical data such as mass, volume, or pH.

Accuracy vs Precision Accuracy ◦ Describes how close an experimental determined value is compared to the known or true value. Precision ◦ Describes how close the experimental trials are to each other.

Accurate, Precise, Both, Neither Accurate, Precise, Both, Neither 78.1mL, 43.9mL, 2mL

Percent Error |Experimental Value – Theoretical Value| x 100 Theoretical Value A student measured the string as 1.25m long. The teacher said it was actually 2.12m long. What was the student’s percent error?

Graphing Data TrialTemp.Volume

Sources of Error Procedural error ◦ Are you missing steps in your procedure? ◦ Are steps of your procedure making incorrect assumptions? ◦ Are you incorrectly measuring your product/result? Systematic error ◦ Consistently causes measurements to be too high or too low (a systematic error will always throw off you measurements by the same amount and in the same direction) Ex: a balance is not properly zeroed or an instrument is not properly calibrated Random error ◦ A source of measurement error due to the estimation of the last significant figure. The more trials run, the less random error will affect your results.

Dimensional Analysis Read Dimensional Analysis on page 11 of the resource notes

Homework Complete Accuracy vs Precision Practice Complete Dimensional Analysis Practice Complete Parts of Experiment Practice