Scientific
measurement
2020
Objectives
- To be familiar with the fundamental and derived units.
- To describe the scientific procedures used to determine magnitudes.
- To make measurements correctly taking into account their errors depending
on the type of measurement.
Using and expressing measurements
In science, measurements must be accurate, precise, and written
to the correct number of significant figures
Compare accuracy and precision
Accuracy
Precision
Error is the difference between the measured value and the accepted value.
Add the term error in the correct location in your Venn diagram
Practice
Percent Error (%e)
Error = experimental value - accepted value = Absolute Error
Example:
Percent error =
|error |
x 100
(Relative error)
accepted value
Example: An object is weighed on a very accurate balance (accepted value)
which says the weight is 108.2 g. Later you weigh it on another balance and
register that the weight is 108.5 g. What is the percent error?
Practice
A measurement was taken three times. The correct measurement was 68.1 mL.
Circle whether the set of measurements is accurate, precise, both or neither.
Practice
Significant figures (Cifras significativas)
Practice
How many significant figures are in each
measurement?
a. 123 m
b. 40,506 mm
c. 9.8000 x 104 m
d. 0.070 80 m
e. 98,000 m
International System of Units
(Sistema Internacional de Unidades)
● The metric system was originally established in
France in 1960.
● The International System of Units (abbreviated SI, for
Système International d’Unités) is a revised version of
the metric system, and it was adopted by international
agreement in 1960.
● In this system, there are seven base units.
Natural constants redefinition of the base units in the SI
Source: Physikalisch-Technische Bundesanstalt
(The National Metrology Institute). goo.gl/bfk1GE
Prefixes: to
express
magnitude
Re-write the following using PREFIX and UNIT
SYMBOLS and the FACTOR it represents:
1.
2.5 centimetres →
2. 25.2 millimoles
3. 0.25 megalitres
4. 1.3 kilograms
5. 5.1 decigrams
6. 6.38 micrograms
2.5 cm; 2.5 x 10-2 m
UNIT CONVERSION - Examples
Length
MASS
Re-write the following using PREFIX SYMBOLS, and
WRITTEN PREFIXES and UNITS
1. 4.5 x 10-3 mol →
2. 0.50 x 10-6 L
3. 8.85 x 106 s
4. 1.6 x 103 m
5. 2.68 x 10-1 g
6. 7.25 x 10-2 m
4.5 mmol; 4.5 millimoles
Re-write the following using PREFIX and UNIT
SYMBOLS and the FACTOR it represents:
1.
2.5 centimetres →
2. 25.2 millimoles
3. 0.25 megalitres
4. 1.3 kilograms
5. 5.1 decigrams
6. 6.38 micrograms
2.5 cm; 2.5 x 10-2 m
Metric Prefixes - Ladder Method
Try these conversions
100 cm = 0.1 m
Write the correct abbreviation for each metric unit.
Compare using <, >, or =.
Temperature
Scales
Temperature Scales Conversion
Temperature Conversion
Convert the following to Kelvin
Convert the following to Celsius
●
0oC
________
●
100 K
●
-50oC ________
●
273 K ________
●
90oC
________
●
625 K ________
●
-20oC ________
●
310 K ________
________
Temperature Conversion
Convert the following to Fahrenheit
Convert the following to Celsius
●
0oC
________
●
32ºF
________
●
-50oC ________
●
90ºF ________
●
90oC
________
●
350ºF ________
●
-20oC ________
●
175ºF ________