Unit 1 Scientific Method + Measurement
Post on 22-Feb-2016
107 Views
Preview:
DESCRIPTION
Transcript
Unit 1Scientific Method
+Measurement
Chem 1Fall 07
Scientific Method
Scientific Method (cont.)• People often confuse
– Observations & Hypotheses
• An observation…– Is information
collected with the senses
• A hypothesis…– Is a theory about the
natural world that needs to be tested
Ivan Pavlov observed dogs salivating and
hypothesized that a sound would cause
dogs to salivate.
Scientific Method (cont.)
• People also often confuse– Controls & Variables
• A control is…– A trial that duplicates all conditions except
the variable being investigated• A variable is…
– The thing being tested
Practice Problem #1• Identify the following as an observation or a
hypothesis– 1. Wearing tennis shoes will make one run faster.
– 2. The tennis shoes are black and red.
– 3. The Bunsen Burner flame is 1400°C and is blue.
– 4. People who take good notes will do better on tests.
Hypothesis
Observation
Observation
Hypothesis
Types of Observations
• Scientists make observations all the time.• There’s two types:
– Qualitative– Quantitative
• To remember the difference, look at their root
Qualitative Observations
• Qualities of the reaction, object, etc.• Example
– The copper (II) sulfate is blue– The nail is rusty– Gas was given off
Quantitative Observations
• Quantity= numbers• Mass, a number of paper clips, volume
measurements, molar measurements. • Math is usually involved
Metrics
• Metric system is much easier than the English system…the conversion is always a factor of 10.
Length is a 1-dimensional measure of distance. Metric system base unit is the
meter, abbreviated m
Metrics (cont.)• Mass is a measure of the amount of
matter in a substance.– Metric system base unit is the
kilogram, abbreviated kg
Volume is a measure of the amount of space a substance takes up.
Metric system base unit is the liter, abbreviated L.
Weight• Response of
mass to the pull of gravity
• Weight changes when on different planets
• NOT THE SAME AS MASS!
Metrics (cont.)
• Kilo hecto deka (m, g, L) deci centi milli• k h dk or D d c m
– How do you remember the order of the prefixes?
Metric Prefixes
Kilo hecto deka (m, g, L) deci centi milli k h dk d c m
103 102 101 10-1 10-2 10-3
How do you remember the order of the prefixes?
Practice Problem #2
• Make the following metric conversions– 1. 875 cm = _________ m.
– 2. 1.24 km = _________ m.
– 3. 90,344 m = _________ km.
– 4. 0.95 km = _________cm.
9.75
1,240
90.344
950,000
Accuracy and Precision
• Accuracy– Close to the true
or desired value• Precision
– Reproducible measurements
Measurement• There is always an
error in a measurement
• The human eye can read one decimal place beyond the accuracy of the instrument
The measurement should be read as 8.0 +/-0.1cm.
Practice Problem #3
65
60
55
10
9
8
150
100
50
Container #1 Container #2 Container #39.02 mL 82 mL 62.0 mL
Read the volumes of the liquids below
top related