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Title: Measurements and Calculations
Description: Chemistry measurements and calculations. Chapter 2.
Description: Chemistry measurements and calculations. Chapter 2.
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Chapter II
Measurements and Calculations
Measurements
A quantity is something that has size, magnitude, or amount
...
The unit is defined by some physical characteristics in nature
...
EX
...
A derived unit is one formed from a combination of base unites
...
area (m^2), volume (m^3), density (kg/m^3)
Kilo = 1000 of
Centi = 1/100 of
Millie = 1/1000 of
Density
Density is the mass of an object divided by its volume
...
Units for Density
g/ml
g/cm^3
k/m^3
g/l
Water
1
...
35 g/ml
Cork
0
...
How close we can get to the exact value of the measurement depends on the
sensitivity of the measuring device
...
Rules for counting significant figures
1
...
2
...
Leading zeros are zeros there proceed all the nonzero digits (don't count as
significant figures)
...
Captive zeros are zeros between nonzero digits (always count as significant
figures)
...
Trailing zeros are zeros at the end of the number (counted as significant figures
only if the number contains a decimal point)
...
Addition and Subtraction
The answer should have as many digits to the right of the decimal point as there are in the
measurement having the fewest to the right of the decimal point
...
Error analysis
1
...
Percent error
% error = EA /A x 100
Graphical Analysis
An independent variable is assigned to specific values in an experiment
...
Independent variable is graphed on the X axis
...
Proportions - ∝ means “proportional to”
2/3 equals 4/6 – Proportion is having the same or a constant ratio
...
Direct proportion - both variables increase by the same factor
...
2
...
Density ∝ 1/Volume ; D = K (1/V)
Title: Measurements and Calculations
Description: Chemistry measurements and calculations. Chapter 2.
Description: Chemistry measurements and calculations. Chapter 2.