Introduction to Chemistry

• Chemistry is the study of matter and its properties as well as how matter changes
• It is a natural science that studies the composition, structure, properties, and reactions of matter
• Chemistry concerns the study of atoms and their interactions with other atoms
• Chemistry concerns the formation of new substances through chemical reactions
• Chemistry is sometimes called the "central science" because it connects other natural sciences like physics, geology, and biology
• Chemistry is applied across a wide variety of fields, including medicine, agriculture, and manufacturing

Branches of Chemistry

• Analytical chemistry studies the chemical components of natural and artificial materials
• Biochemistry studies chemical processes in living organisms
• Inorganic chemistry studies the properties and reactions of inorganic compounds
• Organic chemistry studies the structure, properties, and reactions of organic compounds, which contain carbon
• Physical chemistry applies physics to the study of chemical systems

Matter

• Matter is anything that has mass and takes up space (volume)
• Matter exists in different states, including solid, liquid, gas, and plasma
• Solids have a definite shape and volume
• Liquids have a definite volume but take the shape of their container
• Gases have no definite shape or volume and can be compressed or expanded
• Plasma is a state of matter where a gas becomes ionized and carries an electrical charge
• Matter can be classified into two main categories: pure substances and mixtures
• Pure substances have a fixed composition and distinct properties, and are either elements or compounds
• Mixtures are combinations of two or more substances that are physically combined

Elements

• An element is a pure substance that cannot be broken down into simpler substances by chemical means, and is composed of only one type of atom
• Atoms are the basic building blocks of matter and consist of protons, neutrons, and electrons
• Protons have a positive charge, neutrons have no charge, and electrons have a negative charge
• The number of protons in an atom determines the element's atomic number
• Elements are organized in the periodic table based on their atomic number and chemical properties
• Elements in the same group (vertical column) of the periodic table have similar chemical properties
• Metals, nonmetals, and metalloids are the three main types of elements

Compounds

• A compound is a pure substance consisting of two or more different elements chemically bonded together in a fixed ratio
• Compounds can be broken down into simpler substances by chemical means
• Chemical formulas represent compounds, using symbols to indicate the elements and subscripts to indicate the number of atoms of each element
• Molecular compounds are formed through covalent bonds, where atoms share electrons
• Ionic compounds are formed through ionic bonds, where electrons are transferred between atoms, creating ions

Mixtures

• A mixture is a combination of two or more substances that are physically combined, and can be either homogeneous or heterogeneous
• Homogeneous mixtures have a uniform composition throughout
• Heterogeneous mixtures have a non-uniform composition throughout
• Mixtures can be separated by physical means, such as filtration, distillation, or evaporation

Chemical Reactions

• A chemical reaction is a process that involves the rearrangement of atoms and molecules to form new substances
• Chemical equations represent chemical reactions, using symbols and formulas to show the reactants (starting materials) and products (substances formed)
• Chemical reactions involve the breaking and forming of chemical bonds
• Energy is either absorbed or released during a chemical reaction
• Exothermic reactions release energy, while endothermic reactions absorb energy
• Activation energy is the minimum energy required for a chemical reaction to occur
• Catalysts speed up chemical reactions by lowering the activation energy

Chemical Quantities

• The mole is the SI unit for measuring the amount of a substance
• Avogadro's number (6.022 x 10^23) is the number of entities (atoms, molecules, ions, etc.) in one mole of a substance
• Molar mass is the mass of one mole of a substance, usually expressed in grams per mole (g/mol)
• Stoichiometry is the study of the quantitative relationships between reactants and products in chemical reactions
• Stoichiometry allows us to predict the amount of reactants and products involved in a chemical reaction
• Limiting reactant is the reactant that is completely consumed in a chemical reaction, determining the maximum amount of product that can be formed
• Percent yield is the ratio of the actual yield (amount of product obtained) to the theoretical yield (amount of product predicted by stoichiometry), expressed as a percentage

Acids and Bases

• Acids are substances that donate protons (H+) in aqueous solutions
• Bases are substances that accept protons (H+) in aqueous solutions
• pH is a measure of the acidity or basicity of a solution
• pH values range from 0 to 14, where 0-7 is acidic, 7 is neutral, and 7-14 is basic
• Strong acids and bases completely dissociate in water, while weak acids and bases only partially dissociate
• Acid-base reactions involve the transfer of protons from an acid to a base
• Neutralization is the reaction between an acid and a base, which produces a salt and water
• Buffers are solutions that resist changes in pH upon the addition of small amounts of acid or base