Transcript File

Video 1.1 Metric
fractions of an inch...
12 inches to a foot….
3 feet to a yard….
5.5 yards to a rod...
320 rods to a mile...
43,560 sq ft to an acre...
But almost all other countries use the metric
system, which is disadvantageous for us.
We buy cola in liters...
We buy memory cards in bites…
We run 10 km races...
We swim in 25 meter pools...
Why haven’t we switched entirely to metric?
 When
measuring a person we would use
meters.
 If we are measuring an ant, would meters
still be feasible? What should we use?
 If we are measuring the distance from
your house to the school, what should we
use?
 Always pick a prefix with a value close to
what you are measuring.
 If
a unit is getting larger (m  km) the
number must get smaller. [If the unit gets
smaller (m  cm) the number gets
larger.]
 Examples:
• 1. 23.5cm
= 0.000235 km
• 2. 3567mL
=
L
3.567
• 3. 0.0984g
=
ug
98400
 Notice
that each
scales is marked with
BP and FP of water as
well as absolute zero.
 The degree size of
Celsius is equal to
Kelvin. Therefore we
adjust only for zero
points: C = K – 273
K = C + 273
 -10°
Celsius = frigid (14° F)
 0° Celsius = cold (32° F)
 10° Celsius = cool (50° F)
 20° Celsius = comfortably warm (68°
F)
 30° Celsius = hot (86° F)
 40° Celsius = very hot (104° F)
 50° Celsius = Phoenix Hot (120°F)
Video 1.2 Scientific Notation
What is the purpose for using
scientific notation in science?
M x 10n M is between 1 and 10
n is the number of decimal
spaces moved to make M
1.
2.
3.
4.
Find the decimal point. If it is not written,
it is at the end of the number.
Move the decimal point to make the
number between 1 and 10
Place the number of space you moved
the decimal in the n spot.
If you original number was above 1, the
exponent is positive. If the number was
smaller that 1, the exponent is negative.
 1020000
is equal to
• 1.02x106
 0.00789 is equal to
• 7.89x10-3
 3.45x105 is equal to
• 345000
 1.23x10-4 is equal to
• 0.000123
Multiplication and Division:
1.
2.
Multiply or divide the base numbers.
When multiplying, add exponents.
When dividing, subtract exponents.
(8x105)(2x103) = 16x108 or 1.6x109
(8x105)/(2x103) = 4x102
Addition and Subtraction:
The exponents must be the same. Change
your numbers to make this possible.
2. Add or subtract base numbers and do not
change the exponent.
* Remember: if the decimal move makes the
base number smaller, the exponent
increases.
1.
5x105 + 3x104 = 5x105 + 0.3x105 = 5.3x105
Video 1.3 Significant Figures
 Precision: reproducibility, repeatability
 Accuracy: closeness
to the correct answer
1. A student obtains the following data:
2.57mL
2.59mL
2.58mL
2.98mL
Compare these pieces in terms of
precision and accuracy.
Describe these
diagrams in terms
of precision and
accuracy:
The first shows
precision, not accuracy.
The second shows
accuracy, not precision.
In this classroom, what
is more important:
Precision or
Accuracy?
Due
to lack of precise equipment
and variable climates we will
most likely not end up with
accurate results. Therefore, we
will focus on refining our lab
skills and strive for precise
results.
 When
scientists take measurements their
equipment can measure with varying
degrees of precision.
 A scientists final calculation can only be
as precise as their least precise
measurement.
 Count digits in your measured number to
determine their level of precision.
 All
natural numbers 1-9 count once.
 569 has 3SF
 The
3.456 has 4SF
number zero is tricky…
• Zeros always count between natural numbers:
 109 have 3SF
50089 has 5SF
• Zeros before a decimal and natural number
never count.
 0.00789 has 3SF
001234 has 4SF
• Zeros after natural numbers only count IF there
is a decimal present.
 100 has 1SF
100. has 3SF
100.0 has 4SF
 Remember: you
can only be as precise as
your least precise measurement.
Therefore, when adding and subtracting,
round your answer to the least number of
DECIMAL PLACES.
 2.0 + 5.61 = 7.61 = 7.6
 5.67 + 102.111 = 107.781 = 107.78
 23 + 11.10 = 34.10 = 34
 Remember: you
can only be as precise as
your least precise measurement.
Therefore, when multiplying or dividing,
round your answer to the least number of
significant figures.
 2.0 x 35.1 = 70.2 = 70.
 5.11 x 98.654 = 504.12194 = 504
 72.1 / 3.123 = 23.0867755 = 23.1