BackCHEM101 Study Notes: Matter, Scientific Method, and Significant Figures
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Matter and Measurements
Introduction to Chemistry and Science
Chemistry is the study of matter, its properties, composition, structure, and the changes it undergoes. Matter is defined as anything that has mass and takes up space. The scientific method is a systematic way of studying the world, involving observation, investigation, and explanation.
Matter: Anything with mass and volume (e.g., water, air, living organisms).
Chemistry: Focuses on the composition, structure, properties, and reactions of matter.
Scientific Method: A multi-step process used to investigate phenomena and solve problems in science.
Diagram: Matter is central to chemistry, with branches for composition, structure, properties, and reactions.
Key Definitions in Chemistry
Word | Definition |
|---|---|
Chemicals | Substances with the same composition and properties wherever found |
Atoms | A particle that defines an element |
Element | A substance that cannot be broken down further |
Molecules | A group of atoms bonded together |
Examples of Molecules:
Object | Chemicals | Function |
|---|---|---|
Soda | Water, carbon dioxide | Beverage |
Toothpaste | Calcium carbonate, sorbitol, sodium lauryl sulfate, etc. | Keep your teeth clean |
Window | Silicon dioxide | Let you look outside while not exposing you to the elements |
The Scientific Method
The scientific method is a powerful tool for learning about the world. It involves observation, research, hypothesis formation, experimentation, and analysis.
Step 1: State the problem as a question
Step 2: Research
Step 3: State a hypothesis
Step 4: Experiment
Step 5: State results
Step 6: State your conclusion
Example: Determining the most efficient route for travel by testing different variables and analyzing outcomes.
Significant Figures in Measurements
Significant figures communicate the precision of a measurement. Every measured number has a certain degree of uncertainty, which is expressed through significant figures.
Rule 1: All nonzero digits are significant (e.g., 123 has 3 significant figures).
Rule 2: Interior zeros (zeros between nonzero digits) are significant (e.g., 101 has 3 significant figures).
Rule 3: Trailing zeros after a decimal point are significant (e.g., 1.00 has 3 significant figures).
Rule 4: Trailing zeros before a decimal point are significant (e.g., 1000. has 4 significant figures).
Rule 5: Leading zeros (zeros to the left of the first nonzero digit) are NOT significant (e.g., 0.001 has 1 significant figure).
Rule 6: Trailing zeros at the end of a number, but before an implied decimal point, are ambiguous and should be avoided.
Exact Numbers: Have unlimited significant figures (e.g., counting objects).
Example: 0.00357 has 3 significant figures (the zeros are not significant).
Examples and Practice with Significant Figures
Number | Significant Figures | Rules Applied |
|---|---|---|
1.080 | 4 | 1, 2, 6, 3 |
2371 | 4 | 1 |
2.9 × 102 | 2 | 1 |
1 dozen = 12 | unlimited | Exact number |
100.00 | 5 | 1, 3, 6, 4 |
100,000 | 1 | 6 |
Significant Figures in Calculations
When performing calculations, significant figures must be considered to ensure the accuracy of results.
Multiplication and Division: The answer should have the same number of significant figures as the factor with the fewest significant figures.
Addition and Subtraction: The answer should have the same number of decimal places as the measurement with the fewest decimal places.
Example (Multiplication):
(2 has 1 significant figure, 3.1 has 2; answer rounded to 1 significant figure: 6)
Example (Addition):
0.12 cm has 2 decimal places, so the answer is rounded to 2 decimal places: 4690.53 cm
Practice Problems and Solutions
Equation | Answer (not rounded) | Answer with significant figures | Rule |
|---|---|---|---|
5.623 + 0.3 | 5.323 | 5.3 | Fewest decimal places |
103.4 / 2.4 | 43.083333 | 43 | Least # of sig figs |
1.332 × 0.4 | 0.5328 | 0.5 | Least # of sig figs |
1533.0 + 0.0034 | 1533.0034 | 1533.0 | Fewest decimal places |
Additional Practice: Identifying Significant Figures
Number | Number of Significant Figures |
|---|---|
15000 | 2 |
0.0037 | 2 |
1.62 × 105 | 3 |
670 | 2 |
Example: 4.38 - 3.965 = 0.415 (rounded to 2 decimal places: 0.42)
Summary
Chemistry studies matter, its properties, and changes.
The scientific method is essential for investigation and problem-solving.
Significant figures communicate the precision of measurements and must be considered in calculations.
Additional info: These notes cover foundational concepts for GOB Chemistry, including matter, measurement, and the scientific method, with detailed rules and examples for significant figures.
