Chapter 1: The Scientific Method Chemistry = The science that seeks to understand what matter does...
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Transcript of Chapter 1: The Scientific Method Chemistry = The science that seeks to understand what matter does...
Chapter 1: The Scientific Method
Chemistry = The science that seeks to understand what matter does by studying what atoms and molecules do.
Observation = A way of acquiring information about nature.
• Simple descriptions (qualitative observation)• Number (quantitative observation)
Hypothesis = A tentative explanation of your observations• Falsifiable: a test may invalidate your hypothesis
Experiments = Tests of hypotheses, laws or theories• Results either Validate (confirm) or Invalidate (deny) your ideas
Law = A statement that combines all past observations• Predict future observations• You cannot choose to violate a scientific law
Theory = An explanation that extends beyond individual observations to an understanding of the underlying causes for the way nature is or behaves
• Models of nature
This is what the scientific method is made of
Observations
Hypothesis
Law
Theory
Experiments
Experiments
Experiments
This is how the scientific method works
http://www.youtube.com/watch?v=5Owji16tge0
The (meaningful) beauty of the scientific method
Source: http://www.meaningfulbeauty.com/theStory.php
Measurement = Quantitative observation• Comparison to an agreed upon standard• Every measurement has a number and a unit
Scientists have measured the average global temperature rise over the past century to be
0.6 °C The number tells you
1. what multiple of the standard the object measures
2. the uncertainty in the measurement
The unit tells you what standard you are
comparing your object to
Chapter 2: Measurements and Problem Solving
Scientific Notation is a way of writing large and small numbers
The sun’s diameter is1,392,000,000 m
An atom’s average diameter is0.000 000 000 3 m
The sun’s diameter is1.392 x 109 m
An atom’s average diameter is3 x 10-10 m
Large Number = Positive Exponent
1.392 x 109 m
Small Number = Negative Exponent
3 x 10-10 m
Writing a number in scientific notation
1,392,000,000 m
1. Locate the decimal point2. Move the decimal point until a number
between 1 and 10 is obtained 3. Multiply the new number by 10n
4. n is the number of places you moved the decimal point
5. Large number? n is positiveSmall number? n is negative
1,392,000,000. m
1.392,000,000. m
1.392 x 10 ? 9 m
1.392 x 10 9 m
Significant Figures Writing Numbers to Reflect Precision
Exact Values• Can be obtained by counting or by definition• Exact values have “unlimited significant figures”
Measurements• Are obtained from instruments• The number of significant figures reflects the instrument precision. All the digits written are known with certainty except the last one, which is an estimate
1.2 gramsCertain
Estimated
Counting Significant Figures
0.003004500 m1. Non-zero digits are significant2. Zeroes in between non-zero digits are significant 3. Zeroes on the right of the last non-zero digit are significant4. Zeroes on the left of the first non-zero digit are not significant
Important exception 1: Exact numbers.Numbers that come from1. Counting2. FormulasAre not measurements and have an infinite amount of sig. fig.
Important exception 2: Ambiguous numbers.A number has an ambiguous amount of sig. fig. if:1. It is bigger or equal to 102. It has no decimals3. It ends with a zero
10 Fingers >
100 Miles
How many significant figures are in each of the following numbers?
0.0035
1.080
2371
2.97 × 105
12 items (In a dozen)
100,000
Counting Significant Figures. Examples.
Multiplication and Division with Significant Figures
When multiplying or dividing measurements with significant figures, the result has the same number of significant figures as the measurement with the fewest number of significant figures
5.02 × 89,665 × 0.10 = 45.0118 = 45 3 sig. figs. 5 sig. figs. 2 sig. figs. 2 sig. figs.
5.892 ÷ 6.10 = 0.96590 = 0.966 4 sig. figs. 3 sig. figs. 3 sig. figs.
Addition and Subtraction with Significant Figures
When adding or subtracting measurements with significant figures, the result has the same number of decimal places as the measurement with the fewest number of decimal places
5.74 + 0.823 + 2.651 = 9.214 = 9.21 2 dec. pl. 3 dec. pl. 3 dec. pl. 2 dec. pl.
4.8 - 3.965 = 0.835 = 0.8 1 dec. pl 3 dec. pl. 1 dec. pl.