teaching the metric system sally b. mitchell sallybchemistry.com for meaning and understanding
Post on 28-Dec-2015
224 Views
Preview:
TRANSCRIPT
Teaching the Metric System
Sally B. Mitchell sallybchemistry.com
For meaning and understanding
Identify the problem
Engineer a Solution to a problem with education
7 years of research
Writing to learn
Re-teach teachers (keep an open mind)
Numbers
How many ways can you express this number?
Three hundred million
Normal Notation
300,000,000
Scientific Notation
3 x 108
Engineering Notation
300 x 106
Metric Notation
300 M
Ways to express quantities
Written notation (three hundred million)
Number notation (300,000,000)
Scientific notation ( 3 x 108)
Engineering notation ( 300 x 106)
Metric notation ( 300 M)
Infinite number of other ways ( 30 x 107)
What is a metric prefix?
Quantity?
Number?
Symbol?
Why do we even use prefixes?
Easier to write
Easier to say
Easier to manipulate
It is concise
Do you know your prefixes?
10-12 10-9 10-6 10-3 100 103 106 109 1012
p n μ m k M G T
Try another0.000 000 000 032
Notice the spaces between groups of 3 numbers
3.2 x 10-11 (Scientific Notation)
32 x 10-12 (Engineering Notation)
32 p (Metric Notation)
What is the appropriate prefix for this quantity?
The time was 45,000,000,000 seconds
45 Gs
The distance between the objects was 0.000 050 m
50 μm
Why change the prefix?Yet, we assess the student’s ability to CONVERT
from kilometers to nanometers on the first day of class!
Convert 2 km to nm
REALLY? Is this a conversion?
Sound Mathematical Principles
2 x 103 m
Multiplicative Identity and Multiplicative Inverse
2 x 103 x ( ) m10-9109 x
Associative Law and
Law of Exponents
(2 x 103 x 109 ) x 10-9 m
2 x 1012 x 10-9 m
Substitution of Symbol
2 x 1012 nm
Check it
2 km = 2 x 1012 nm?
Look at only the quantity
2 k = 2 x 1012 n?
2 x 103 = 2 x 1012 x 10-9
Calculate the density of radon gas at STP
Mass = 450 mg Volume = 50 mL
Express your answer in g/L
Density = 9 g/L
100 % confidenceTeach about numbers and different ways to
express
Review Scientific Notation
Introduce Engineering Notation
Discuss prefixes
Remember to develop “Prefixes are symbols”
Challenge your students to express quantities using different symbols
Remember
NO DIMENSIONAL ANALYSIS
No tricks
No centi
Groups of 3 (300,000,000 0.000 000 000 032)
What is a MOLE?
6.02 x 1023 ?
602 x 1021 ?
top related