Transcript SI Units, Base Units, Measurements and Significant Figures PowerPoint

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 Objectives
Introduction 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
Examples
Branch
Organic
chemistry
Inorganic
chemistry
Area of Emphasis
most carbon-containing chemicals
Physical
chemistry
the behavior and changes of matter
reaction rates,
and the related energy changes
reaction mechanisms
in general, matter that does not
contain carbon
pharmaceuticals,
plastics
minerals, metals and
nonmetals, semiconductors
Analytical
chemistry
components and composition of
substances
food nutrients,
quality control
Biochemistry
matter and processes of living
organisms
metabolism,
fermentation
Units of measurement
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.
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/gradc
yl.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.
2.
3.
4.
5.
All digits 1-9 are significant.
Zeros between significant digits
are always significant.
Trailing 0’s are significant only if
the number contains a decimal
point
Zeros in the beginning of a
number with a decimal point are
not significant.
Zeros following a significant
number with a decimal are
significant.
Significant Figures


Pacific to Atlantic Pacific = Decimal Present
Rule
Start from the Pacific (left hand
side), every digit beginning
with the first 1-9 integer is
significant
Examples
20.0 = 3 sig digits
0.00320400 = 6 sig digits
1000. = 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 digits
1000 = 1 sig digits
Practice

1.
2.
3.
4.
How many significant figures are in
400.0
4000
4004
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.
2.
Measurement Worksheet 1
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
 Universal
Analysis
– 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 • A more formal definition of
Matter is anything that
Central Science
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 Ball
Volley Ball
Example

Which of the following weighs more?
A
ton of feathers?
 A ton of bricks?
Units of measurement
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.
Base Units
Why do we use the metric system?

Advantages
 Simple
to use
 Easy to convert from one unit to another
 Dimensional
 Universal
Analysis
– 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.wisconline.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/gradc
yl.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