Ch. 1 - Matter, Measurement & Problem Solving

Scientific and Standard Notation

Scientific notation is a method for expressing very large or very small numbers using powers of ten. Standard notation is the usual way numbers are written.

• Scientific Notation: Numbers are written as a × 10n, where a is a number between 1 and 10, and n is an integer.

• Standard Notation: Numbers are written out in their usual decimal form.

• Example: (scientific notation) is Avogadro's number; in standard notation: 602,000,000,000,000,000,000,000.

Significant Figures

Significant figures (sig figs) are the digits in a measurement that are known with certainty plus one digit that is estimated.

• Counting Significant Figures: All nonzero digits are significant; zeros between nonzero digits are significant; leading zeros are not significant; trailing zeros are significant only if there is a decimal point.

• Rules in Calculations: For multiplication/division, the result should have the same number of sig figs as the measurement with the fewest sig figs. For addition/subtraction, the result should have the same number of decimal places as the measurement with the fewest decimal places.

• Example: (rounded to two sig figs).

Temperature Conversions

Temperature can be measured in Celsius (°C), Kelvin (K), and Fahrenheit (°F). Conversions between these scales are important in chemistry.

• Celsius to Kelvin:

• Celsius to Fahrenheit:

• Fahrenheit to Celsius:

• Example: Convert 25°C to Kelvin: K.

Unit Conversions

Unit conversions involve changing a measurement from one unit to another using conversion factors. Problems may involve units squared (area) or cubed (volume).

• Conversion Factor: A ratio used to convert from one unit to another.

• Example: To convert 5.0 cm3 to m3:

• Area and Volume: Remember to apply conversion factors to each dimension (e.g., for area, square the conversion factor; for volume, cube it).

SI Prefixes

SI prefixes are used to denote multiples or fractions of units. Each prefix corresponds to a specific power of ten.

• Common SI Prefixes:

• Example: 1 kilometer = meters.

Density

Density is a physical property defined as mass per unit volume. It is often used in laboratory experiments to identify substances or calculate mass/volume relationships.

• Formula:

• Units: Common units are g/cm3 or kg/m3.

• Example: If a sample has a mass of 10.0 g and a volume of 2.0 cm3, its density is .

Ch. 2 - Atoms & Elements

Basic Components of the Atom

An atom consists of three fundamental subatomic particles: protons, neutrons, and electrons. Their arrangement is described by the nuclear model.

• Protons: Positively charged particles located in the nucleus; determine atomic number.

• Neutrons: Neutral particles located in the nucleus; contribute to atomic mass.

• Electrons: Negatively charged particles found in orbitals around the nucleus.

• Nuclear Model: Protons and neutrons are in the nucleus; electrons occupy the space around the nucleus.

• Example: Carbon atom: 6 protons, 6 neutrons, 6 electrons.

Isotopic Symbols

Isotopic symbols represent specific isotopes of elements, showing atomic number, mass number, and elemental symbol.

• Format: , where A is mass number, Z is atomic number, and X is the element symbol.

• Finding Elemental Symbol: Use the periodic table to match atomic number to element.

• Example: represents carbon-14 (6 protons, 8 neutrons).

Formation of Ions

Ions are atoms or molecules that have gained or lost electrons, resulting in a net charge. The charge affects the number of subatomic particles present.

• Cation: Formed when an atom loses electrons; positive charge.

• Anion: Formed when an atom gains electrons; negative charge.

• Effect on Subatomic Particles: The number of protons remains unchanged; the number of electrons changes according to the charge.

• Example: Na+ ion: 11 protons, 10 electrons.

Lab Techniques and Procedures (Additional info)

Density Measurement in Laboratory

Density is often determined experimentally by measuring mass and volume of a sample. Common techniques include using a balance for mass and graduated cylinder for volume.

• Procedure: Measure mass using a balance; measure volume using displacement or direct measurement.

• Calculation: Use the formula .

• Application: Used to identify unknown substances or verify purity.

Additional info: Lab techniques and SI prefixes table were expanded for completeness and academic context.