Data Analysis

Applying Mathematical Concepts to Chemistry

Scientific Notation concise format for representing extremely

large or small numbers Requires 2 parts:

Number between 1 and 9.99999999… Power of ten Examples:

6.02 x 1023 = 602,000,000,000,000,000,000,000

2.0 x 10 -7 m = 0.0000002 m Use calculator to solve problems on p. 788-789

Accuracy vs Precision

Accuracy- closeness of measurements to the target value Error- difference

between measured value and accepted value (absolute value)

Precision- closeness of measurements to each other

Percent Error

%error = (accepted-experimental) x 100 accepted

EX: The measured mass is 5.0g. It was predicted that the accepted value should have been 6.0 g.

% error = 6.0g-5.0g x 100 = 16.7%

6.0g

Significant Figures

Measurements are limited in their sensitivity by the instrument used to measure

Estimating Measurements

Read one place past the instrument

35.0 mL is saying the actual measurement is between 34.9 and 35.1 mL

Why Significant Figures?

Measurements involve rounding

Multiplying/dividing or adding/subtracting measurements can not make them more accurate

Provide a way to tell how sensitive a measurement really is…

5 ≠ 5.0 ≠ 5.00 ≠ 5.000

Recognizing Significant Digits

1. Nonzero digits are always significant 543.21 meters has 5 significant figures

2. Zeros between nonzeros are significant 505.05 liters has 5 sig figs

3. Zeros to the right of a decimal and a nonzero are significant 3.10 has 3 sig figs

Recognizing Sig Figs

4. Placeholder zeros are not significant 0.01g has one sig fig 1000g has one sig fig 1000.g has four sig figs 1000.0g has five sig figs

5. Counting numbers and constants have infinite significant figures 5 people has infinite sig figs

Rule for Multiplying/Dividing Sig Figs

Multiply as usual in calculator Write answer Round answer to same number of sig

figs as the lowest original operator

EX: 1000 x 123.456 = 123456 = 100000 EX: 1000. x 123.456 = 123456 = 123500

Practice Multiplying/Dividing

50.20 x 1.500

0.412 x 230

1.2x108 / 2.4 x 10-7

50400 / 61321

Rule for Adding/Subtracting

Round answer to least “precise” original operator.

EX: 1000

+ 1.2345

1000

Practice Adding/Subtracting

100.23 + 56.1

.000954 + 5.0542

1.0 x 103 + 5.02 x 104

1.0045 – 0.0250

Units of Measure

SI Units- scientifically accepted units of measure: Know:

Length Volume (m3) Mass Density (g/mL) Temperature Time

The Metric System

Metric Practice

623.19 hL = __________ L 1026 mm = ___________cm 0.025 kg = ___________mg

Online Powers of 10 Demonstration:

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/

Good Info to Know

Volume- amount of space an object takes up (ex: liters)

V = l x w x h 1 cm3 = 1 mL by

definition

More Good Info to Know

Mass is different from weight Mass ≠ Weight Mass= measure of the amount of matter

in an object Weight= force caused by the pull of

gravity on an object

***Mass is constant while weight varies depending on the location of an object***

Temperature Scales

Temperature Conversions

Degrees Celsius to Kelvin

Tkelvin=Tcelsius + 273

EX: 25 °C = ? K

Tkelvin=25 +273=298K

Kelvin to Degrees Celsius

Tcelsius=Tkelvin - 273

EX: 210 K = ? °C

Tc= 273–210= -63°C

Derived Quantities- Density

Density- how much matter is in the volume an object takes up.

Density = mass/volume D= g/mL

Determining Density

Mass- measure in grams with balance Volume-

Regular shaped object: measure sides and use volume formula

EX: rectangle V= l x w x h Irregular shaped object: water

displacement

Density by Water Displacement

Fill graduated cylinder to known initial volume

Add object Record final volume Subtract initial

volume from final volume

Record volume of object

Graphing Data

General Rules Fit page Even scale Best fit/trendline Informative Title Labeled Axes

How Does Volume Impact Temperature?