CHEMISTRY

July 30, 2013

Brain Teaser

Turn in Homework: Science Autobiography Write your name and period number

Define Chemistry using your own words What is the SI base unit for the following

measurements (Example: Volume = Liter (L)) Length = ___________ Mass = __________ Temperature = ___________ Time = __________

Agenda

Brain Teaser Notes:

Introduction to Chemistry SI Units and Base Units Significant Figures

Homework Intro to Measurement Worksheet 1 Significant Figures Worksheet (?)

Unit 1 ObjectivesIntroduction to Chemistry

Define chemistry and matter Units of measurement

SI Units Base Units

Accuracy versus Precision Uncertainty in Measurement Significant Figures Significant Figures in Calculations Dimensional Analysis

Introduction to Chemistry

Chemistry: The Central Science

Chemistry is the science that investigates and explains the structure and properties of matter.

Seeks to explain the submicroscopic events that lead to macroscopic observations

Branches of Chemistry

Branch Area of Emphasis Examples

Organic chemistry

most carbon-containing chemicals pharmaceuticals, plastics

Inorganic chemistry

in general, matter that does not contain carbon

minerals, metals and nonmetals, semi-

conductors

Physical chemistry

the behavior and changes of matter and the related energy changes

reaction rates, reaction mechanisms

Analytical chemistry

components and composition of substances

food nutrients, quality control

Biochemistry matter and processes of living organisms

metabolism, fermentation

SI Units (Le Systéme Internationale) Scientists need to report data that can be

reproduced by other scientists. They need standard units of measurement.

Base Units• A base unit is a defined unit in a system of measurement•There are seven base units in SI.

Units of measurement

Base Units

SI Units and Base Units

Handouts Kilo, centi, milli

SIGNIFICANT FIGURES

Significant Figures

Significant Figures

Digits in a measurement that have meaning relative to the equipment being used

Significant Figures Place What is the increment on

the equipment?

What you know for sure.

Significant Figures

Digits with meaning

Digits that can be known precisely plus a last digit that must be estimated.

Scale Reading and Uncertainty

Uncertainty: Limit of precision of the reading (based on ability to guess the final digit). Existed in measured quantities versus counted

quantities Refer to Example (2 rulers)

Ruler

http://www.funbrain.com/measure/

What are the units?

Graduated Cylinder

http://www.uwplatt.edu/chemep/chem/chemscape/labdocs/catofp/measurea/volume/gradcyl/gradcyl.htm

What are the units?

Significant Figures

What do you notice?

Depends on type of equipment being used.

Depends on size of equipment used.

Summary

Things to consider What do significant figures tell you about the

measurement on the equipment?

If you wanted to measure the mass of a whale, what scale would you want to use? Would it matter if you know its mass accurately to 1 gram?

If you wanted to measure the mass a grain of sand , what scale would you want to use? Would it matter if you know its mass accurately to 1 gram?

Significant Figures

Raw Data Rules How do you

know how many sig figs?

1. All digits 1-9 are significant.2. Zeros between significant

digits are always significant.

3. Trailing 0’s are significant only if the number contains a decimal point

4. Zeros in the beginning of a number with a decimal point are not significant.

5. Zeros following a significant number with a decimal are significant.

Significant Figures

Pacific to Atlantic Rule

Examples

Pacific = Decimal Present Start from the Pacific (left

hand side), every digit beginning with the first 1-9 integer is significant

20.0 = 3 sig digits0.00320400 = 6 sig digits1000. = 4 sig digits

Significant Figures

Atlantic Rule to Pacific

Examples

Atlantic = Decimal Absent Start from the Atlantic

(right hand side), every digit beginning with the first 1-9 integer is significant

100020 = 5 sig digits1000 = 1 sig digits

Practice How many significant figures are in1. 400.02. 40003. 40044. 0.004

More Practice Problems

Determine the number of significant figures in the following: 1005000 1.005 0.000125 1000. 0.02002 2002 200.200

Review Questions

Determine the number of significant figures in:

72.3 g 60.5 g 6.20 g 0.0253 g 4320 g 0.00040230 g 4.05 x 105 g 4500. g

Homework

1. Measurement Worksheet 12. Significant Figures 1 Worksheet

THE END

Why do we use the metric system?

Advantages Simple to use Easy to convert from one unit to another

Dimensional Analysis Universal – used worldwide

By all scientists to communicate By all industrialized nations

Except United States U.S. loses billions of dollars in trade

Mass versus Volume

Question: What is the difference between

mass and volume?

Introduction to Chemistry

• Chemistry: The Central Science

• A more formal definition of Matter is anything that takes up space and has mass

• Mass is the measure of the amount of matter that an object contains

• Volume is the amount of space an object takes up.

Example

Refer to the two identical spherical objects below

Bowling BallVolley Ball

Example

Which of the following weighs more? A ton of feathers? A ton of bricks?

SI Units (Le Systéme Internationale) Scientists need to report data that can be

reproduced by other scientists. They need standard units of measurement.

Base Units• A base unit is a defined unit in a system of measurement•There are seven base units in SI.

Units of measurement

Base Units

Why do we use the metric system?

Advantages Simple to use Easy to convert from one unit to another

Dimensional Analysis Universal – used worldwide

By all scientists to communicate By all industrialized nations

Except United States U.S. loses billions of dollars in trade

Example

Convert 3400 milliliters to liters 44 centimeters to meters 277 kilograms to grams

Accuracy Versus Precision

What is the difference between accuracy and precision?

Precision versus Accuracy Precision: is a measure of how closely

an individual measurements agree with one another Can be precise but inaccurate

Accuracy: refers to how closely individual measurements agree with the correct, or “true” value Examples using the dartboard

An archery target illustrates the difference between accuracy and precision.

Accuracy and Precision Measurements

Scale Reading and Uncertainty

Uncertainty: Limit of precision of the reading (based on ability to guess the final digit). Existed in measured quantities versus counted

quantities

Example

Which electronic balance below allows you to obtain a more precise measurement? Why?

A B

Triple Beam Balance

http://www.wisc-online.com/objects/index_tj.asp?objID=GCH202

What are the units?

Ruler

http://www.funbrain.com/measure/

What are the units?

Graduated Cylinder

http://www.uwplatt.edu/chemep/chem/chemscape/labdocs/catofp/measurea/volume/gradcyl/gradcyl.htm

What are the units?

Measurement Activity

Objectives Measure each physical quantity to the

maximum accuracy allowed by the appropriate instrument.

Record measurements and calculations with the appropriate units from the international system of units (SI.)

Measurement Activity Set up assignment

Title, Name, Chemistry, Period, Date Station Rotation

10 Station 3-4 minutes at each station

Refer to Handout Do NOT remove any items from the station Clean Up and Restore each station before

switching

Homework

Homework “Is it worth the risk?” worksheet Sign Lab Safety Contract Study for Lab Safety Test (Monday) Get Supplies for Chemistry

Closure

Reflect on your learning during the lab activity Concepts learned? “Ah-ha” moments? Questions?

SIGNIFICANT FIGURES

Rules for zeros: All zeros count except placeholder zeros

These are the ones that disappear when you write the number in scientific notation.

Zeros between nonzero digits are always significant E.g. 1005 kg (4 sig. fig) and 1.03 (3 sig. fig)

Zeros at the beginning of a number are never significant E.g. 0.02 (1 sig. fig) and 0.0026 (2 sig. fig)

Zeros at the end of a number are significant if the number contains a decimal point 0.0200g (3 sig. fig), 3.0 cm (2 sig. fig), 5000 (1

sig. fig)

Rules for recognizing significant figures

• Non-zero numbers are always significant.• Zeros between non-zero numbers are always

significant. • All final zeros to the right of the decimal place

are significant.• Zeros that act as placeholders are not

significant.• Counting numbers and defined constants have

an infinite number of significant figures.

Review Questions

Determine the number of significant figures in the following: 1005000 1.005 0.000125 1000. 0.02002 2002 200.200

Review Questions

Determine the number of significant figures in:

72.3 g 60.5 g 6.20 g 0.0253 g 4320 g 0.00040230 g 4.05 x 10^5 g 4500. g

Closure

Reflect on your learning today

Homework

Measurement Worksheet 2 Science Safety Test

Wednesday = TOMORROW Element Quiz

Thurs/Fri Lab Notebook

Quadrille Lab Notebook (Graphing paper) OR

Carbonless Copy Lab Notebook

Topics on Unit 1 Test

Lab Safety Measurements SI units Significant Figures, Uncertainty

Accuracy and Precision Understanding Equipments Dimensional Analysis

Intro to Dimensional Analysis