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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
Significant Figures
Significant Figures
Digits in a measurement that have meaning relative to the equipment being used
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)
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
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
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
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.
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
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
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
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
Triple Beam Balance
http://www.wisc-online.com/objects/index_tj.asp?objID=GCH202
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?
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
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