Significant Figures and Measurement Concepts

Significant Figures (Sig Figs)

• Sig figs indicate the precision of a measurement.
• All non-zero digits are significant.
• Zeros between non-zero digits are significant.
• Leading zeros are not significant.
• Trailing zeros in a decimal number are significant.
• Trailing zeros in a whole number without a decimal point are not significant.
• Multiplication and division: The result has the same number of sig figs as the measurement with the fewest sig figs.
• Addition and subtraction: The result has the same number of decimal places as the measurement with the fewest decimal places. Sig figs are not the focus here; decimal places are.

Measurement

• Accuracy refers to how close a measurement is to the true value.
• Precision refers to how close repeated measurements are to each other.
• Common measuring tools include rulers, graduated cylinders, balances, beakers, and thermometers.
• Understanding units of measurement (e.g., meters, grams, liters, degrees Celsius) is crucial.
• Error analysis is essential in evaluating experimental data. This includes systematic and random errors to determine the margin of uncertainty. Potential human error should also be considered.

Lab Safety

• Always wear safety goggles in the lab.
• Tie back long hair and remove loose clothing.
• Know the locations and proper use of safety equipment (e.g., fire extinguisher, eyewash station).
• Handle chemicals with care, following the instructions provided in the lab procedure. Avoid tasting or touching chemicals unless explicitly directed by the teacher.
• Report any accidents immediately to the teacher.
• Never mix chemicals unless instructed and supervised.
• Always pour acids into water, never water into acid.
• Dispose of chemicals properly according to the lab procedure and school guidelines.
• Wash your hands thoroughly after completing an experiment.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.
• Reactants are the substances that enter the reaction. Products are the substances that result from the reaction.
• Chemical equations represent reactions using chemical formulas and symbols.
• Reactants are written on the left side of the arrow; products are written on the right.
• Balanced chemical equations show equal numbers of atoms of each element on both sides of the equation. This is fundamental.
• Types of reactions (e.g., synthesis, decomposition, single replacement, double replacement) have characteristic patterns.
• Some reactions release energy (exothermic), and others absorb energy (endothermic). Understanding energy changes is crucial.

Chemical Formulas

• Chemical formulas represent the composition of a substance using chemical symbols and subscripts.
• Subscripts indicate the number of atoms of each element present in a molecule or compound.
• Empirical formulas show the simplest whole-number ratio of atoms in a compound.
• Molecular formulas show the actual number of atoms of each element in a molecule.
• Structural formulas show the arrangement of atoms within a molecule.
• Chemical nomenclature systems are used to name compounds systematically.
• Ionic compounds are formed by the electrostatic attraction between positive and negative ions.
• Covalent compounds are formed by the sharing of electrons between atoms.
• Understanding the types of chemical bonds is fundamental to understanding compounds and reactions.

This quiz covers the essential principles of significant figures and measurement accuracy and precision. You will explore various rules for determining significant figures, as well as the tools and units commonly used in measurement. Test your understanding and application of these critical concepts in science.