CHEM 102 Final Flashcards

Matter and Its Forms

• Matter is defined as anything that occupies space and possesses mass.
• Forms of matter range from simplest (atoms) to complex (mixtures):
  • Atoms consist of neutrons, protons, and electrons.
  • Elements are collections of the same type of atoms.
  • Compounds are combinations of different elements forming constant compositions through chemical bonds.
  • Mixtures can be homogeneous (uniform composition) or heterogeneous (non-uniform composition).

Changes in Matter

• Physical changes do not alter the chemical formulas of compounds or elements (e.g., phase changes).
• Chemical changes involve breaking down compounds into their constituent elements and entail making and breaking chemical bonds.

Measurements and Uncertainty

• SI units and metric prefixes are essential in scientific measurements.
• All measurements have inherent uncertainty, typically assumed to be ±1 in the last digit.
• Precision refers to the consistency of measurements, while accuracy denotes how close a measurement is to the true value.

Significant Figures and Calculation Rules

• Significant figures include all solid numbers, with specific rules applied to zeros based on their position.
• In addition, calculations ensure answers reflect the least number of decimal places for addition and least significant figures for multiplication/division.
• Dimensional analysis employs units and conversion factors to derive correct answers.

Atomic Structure and Theories

• Dalton's Atomic Theory posits that elements are composed of atoms, with atoms of the same element being identical, compounds having constant compositions, and mass conservation during chemical reactions.
• JJ Thomson demonstrated that particles carry charge and possess mass, indicating the existence of negatively charged fundamental atomic particles.
• Rutherford's experiments revealed that atoms are primarily empty space with a dense nucleus containing protons.

Subatomic Particles

• Protons are positively charged and located in the nucleus, while neutrons are neutral and also found in the nucleus. Electrons are negatively charged and occupy the electron cloud.
• The atomic number (lower left corner) indicates the number of protons, while the mass number (upper left corner) is the total of protons and neutrons.

Ions and Isotopes

• Neutral atoms have equal numbers of electrons and protons. Ions result from the gain or loss of electrons.
• Isotopes represent atoms of the same element with differing neutron counts.

Ionic and Covalent Compounds

• Cations (positively charged) result from electron loss; anions (negatively charged) arise from electron gain.
• Naming conventions:
  • Ionic compounds prioritize cations followed by anions, utilizing base names and Roman numerals for transition metals.
  • Covalent compounds consist of nonmetals, named using prefixes to denote quantities and root modifications for anions.

Chemical Measurements and Calculations

• Avogadro's number is 6.0223 x 10²³ moles.
• Average atomic mass can be calculated based on isotope mass and abundance.
• Molecular formulas provide actual atom quantities in a compound, while empirical formulas reflect the simplest whole number ratios.

Reactions and Limiting Reactants

• Chemical reactions involve bond breaking and forming, adhering to the law of conservation of mass and demonstrating mole relationships between reactants and products.
• Limiting reactants identify the component that yields the lesser amount of product, while percent yield compares actual and theoretical yields.

Solutions and Electrolytes

• A solution is a homogeneous mixture composed of solutes (substances dissolved) and solvents (the dissolving medium).
• Strong electrolytes are ionic compounds that ionize completely, while weak electrolytes only partially dissociate.

Energy Changes in Reactions

• Exothermic reactions release energy, often indicated by a positive ∆H value.
• Electron affinity refers to the energy change during electron gain by an atom and shows erratic trends.

Bonding and Molecular Geometry

• Electrons bond either through ionic (transfer) or covalent (sharing) interactions, affecting electronegativity and bond properties.
• VSEPR theory explains molecular geometry based on electron repulsion, determining shapes like linear, tetrahedral, and octahedral formations.
• Sigma bonds involve head-to-head orbital overlap, while pi bonds result from side-to-side overlap; the bonds determine rotational behavior within molecules.

Intermolecular Forces

• Intermolecular forces are attractions between neighboring molecules that influence their physical states and properties.

Test your knowledge of essential chemistry concepts with these flashcards designed for CHEM 102 at UIUC. Covering definitions and classifications of matter, these cards will help reinforce your understanding in preparation for the final exam.