BackChapters 1 & 2: Chemistry in Our Lives and Chemistry and Measurements – Study Guide
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Chapter 1: Chemistry in Our Lives
The Scientific Method
The scientific method is a systematic approach used in scientific study. It involves making observations, forming hypotheses, conducting experiments, and drawing conclusions.
Observation: Gathering information using the senses or instruments.
Hypothesis: A testable explanation for an observation.
Experiment: A procedure to test the hypothesis under controlled conditions.
Conclusion: A judgment based on the results of the experiment.
Example: If you notice that a plant grows faster in sunlight (observation), you might hypothesize that sunlight increases plant growth. You test this by growing plants with and without sunlight (experiment), and then analyze the results (conclusion).
Chapter 2: Chemistry and Measurements
Scientific Notation and Expanded Notation
Scientific notation is a way to express very large or very small numbers using powers of ten. Expanded notation writes numbers in their full decimal form.
Converting to Scientific Notation: Move the decimal so only one nonzero digit remains to the left, and count the places moved as the exponent of 10.
Converting to Expanded Notation: Multiply the coefficient by 10 raised to the given exponent and write out the full number.
Example: 4,500 = ;
Comparing Numbers
To compare numbers in scientific and expanded notation, convert both to the same format and compare their values.
Example: (2,500) is larger than 1,800.
Metric System: Base Units and Prefixes
The metric system uses base units for measurement and prefixes to indicate multiples or fractions of these units.
Base Units: meter (m) for length, gram (g) for mass, liter (L) for volume, second (s) for time.
Measurement: Always includes a number and a unit (e.g., 5.0 g).
Measured vs. Exact Numbers
Measured numbers are obtained by measurement and have some uncertainty. Exact numbers are counted or defined values with no uncertainty.
Example: 12 eggs (exact), 2.54 cm in 1 inch (exact by definition), 5.2 m (measured).
Significant Figures
Significant figures (sig figs) indicate the precision of a measured number.
Counting Sig Figs: All nonzero digits are significant; zeros between nonzero digits are significant; leading zeros are not significant; trailing zeros in a decimal number are significant.
Rounding: Round to the specified number of significant figures as required.
Example: 0.00450 has three significant figures.
Significant Figures in Calculations
Multiplication/Division: The answer should have the same number of significant figures as the measurement with the fewest significant figures.
Addition/Subtraction: The answer should have the same number of decimal places as the measurement with the fewest decimal places.
Example: (rounded to two sig figs)
Metric Prefixes
Prefixes are used to indicate multiples or fractions of base units by factors of ten.
Prefix | Symbol | Factor |
|---|---|---|
milli- | m | |
centi- | c | |
kilo- | k |
Example: 1 kilometer (km) = 1,000 meters (m); 1 centimeter (cm) = 0.01 meters (m); 1 milligram (mg) = 0.001 grams (g).
Recognizing Equalities
An equality shows the relationship between two units that are equal in value.
Example: 1 m = 100 cm
