Introduction to Chemistry

• Chemistry is the study of matter and its properties as well as how matter changes.

Matter

• Anything that has mass and takes up space (volume) is matter.
• Atoms compose matter.
• Matter exists as a solid, liquid, gas, or plasma.
  • Solids have a fixed shape and volume where particles are tightly packed.
  • Liquids have a variable shape and fixed volume where particles are close but can move.
  • Gases have a variable shape and volume where particles are widely separated.
  • Plasma is an ionized gas with high energy.

Atoms

• The basic building blocks of matter are atoms.
• Atoms consist of protons, neutrons, and electrons.
  • Protons are positively charged particles in the nucleus.
  • Neutrons are neutral particles in the nucleus.
  • Electrons are negatively charged particles orbiting the nucleus.
• Elements consist of only one type of atom.
• The atomic number is the number of protons, defining the element.
• Isotopes are atoms of the same element with varying numbers of neutrons.

Molecules and Compounds

• Molecules form when two or more atoms are held together by chemical bonds.
• Compounds are molecules that contain at least two different elements.
• Chemical formulas represent the number and type of atoms in a molecule or compound.
  • Water (H2O) has two hydrogen atoms and one oxygen atom.

Chemical Bonds

• Chemical bonds are the forces that hold atoms together in molecules and compounds.
• Types of chemical bonds include ionic, covalent, and metallic.
  • Ionic bonds form by transferring electrons between atoms, creating ions.
  • Covalent bonds form by sharing electrons between atoms.
  • Metallic bonds are found in metals, where electrons are delocalized among a lattice of atoms.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms and molecules.
• Reactants are the starting materials.
• Products are the substances formed.
• Chemical equations use symbols and formulas to represent chemical reactions.
• Balancing chemical equations ensures the same number of atoms for each element on both sides.
• Types of chemical reactions include synthesis, decomposition, single displacement, double displacement, and combustion.
  • Synthesis involves two or more reactants combining into a single product.
  • Decomposition involves a single reactant breaking down into two or more products.
  • Single displacement involves one element replacing another in a compound.
  • Double displacement involves two compounds exchanging ions or elements.
  • Combustion involves a substance reacting rapidly with oxygen to produce heat and light.

Stoichiometry

• Stoichiometry deals with quantitative relationships between reactants and products in chemical reactions.
• The mole is the SI unit for the amount of substance.
• Molar mass refers to the mass of one mole of a substance.
• Stoichiometric calculations allow prediction of the amounts of reactants and products.
• The limiting reactant is completely consumed in a reaction, determining the product amount.
• Percent yield is the ratio of actual yield to theoretical yield, expressed as a percentage.

Acids and Bases

• Acids donate protons (H+) or accept electrons.
• Bases accept protons (H+) or donate electrons.
• The pH scale measures the acidity or basicity of a solution.
  • A pH less than 7 is acidic.
  • A pH of 7 is neutral.
  • A pH greater than 7 is basic (alkaline).
• Strong acids and bases completely dissociate in water.
• Weak acids and bases only partially dissociate in water.
• Neutralization is the reaction between an acid and a base, forming a salt and water.

Solutions

• Solutions are homogeneous mixtures of two or more substances.
• A solute is the substance that is dissolved.
• A solvent is the substance doing the dissolving.
• Concentration is the amount of solute in a given amount of solvent or solution.
• Molarity (M) is a unit of concentration, expressed as moles of solute per liter of solution.
• Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature.

Chemical Kinetics

• Chemical kinetics involves the study of reaction rates and affecting factors.
• Reaction rate refers to the change in reactant or product concentration per unit time.
• Factors affecting reaction rates include temperature, concentration, catalysts, and surface area.
  • Higher temperature generally increases the reaction rate.
  • Higher reactant concentrations generally increase the reaction rate.
  • Catalysts speed up reactions without being consumed.
  • Increasing the surface area of a solid reactant generally increases the reaction rate.

Chemical Equilibrium

• Chemical equilibrium occurs when the rates of forward and reverse reactions are equal
• At equilibrium, reactant and product concentrations remain constant.
• The equilibrium constant (K) measures relative amounts of reactants and products.
• Le Chatelier's principle states that a system at equilibrium will shift to relieve stress from changes in conditions.
  • Changes in conditions include temperature, pressure, and concentration.

Thermochemistry

• Thermochemistry studies heat changes associated with chemical reactions.
• Energy is the capacity to do work or transfer heat.
• Heat (q) is the transfer of thermal energy between two bodies at different temperatures.
• Enthalpy (H) is a thermodynamic property representing the sum of internal energy and the product of pressure and volume.
• Exothermic reactions release heat (ΔH < 0).
• Endothermic reactions absorb heat (ΔH > 0).
• Calorimetry measures of heat flow.

Organic Chemistry

• Organic chemistry studies carbon-containing compounds.
• Carbon's ability to form stable bonds with itself and other elements leads to many organic molecules.
• Functional groups are specific groups of atoms within molecules that dictate characteristic chemical reactions.
• Common functional groups include alcohols (–OH), ethers (–O–), aldehydes (–CHO), ketones (–CO–), carboxylic acids (–COOH), and amines (–NH2).
• Hydrocarbons are organic compounds containing only carbon and hydrogen.
  • Alkanes have single bonds between carbon atoms.
  • Alkenes have at least one double bond between carbon atoms.
  • Alkynes have at least one triple bond between carbon atoms.
  • Aromatic compounds contain a benzene ring.
• Polymers are large molecules made of repeating structural units (monomers).
  • Examples include proteins, carbohydrates, nucleic acids, and plastics.

This lesson offers an introduction to the fundamental concepts of chemistry, exploring the definition and properties of matter, its various states (solid, liquid, gas, plasma), and the atomic structure that forms its base. It gives a summary of atoms, elements, and isotopes.