Introduction to Chemistry: Matter and Its Properties

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

Matter

• Matter is anything that has mass and takes up space.
• Matter exists in different states: 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 are easily compressible.
• Plasma is an ionized gas with high energy.
• Matter can be classified into pure substances and mixtures.
• Pure substances have a fixed composition and distinct properties.
• Elements are substances that cannot be broken down into simpler substances by chemical means, e.g., gold (Au), oxygen (O2).
• Compounds are substances composed of two or more elements chemically combined in fixed proportions, e.g., water (H2O), sodium chloride (NaCl).
• Mixtures are combinations of two or more substances that are physically combined.
• Mixtures can be homogeneous or heterogeneous.
• Homogeneous mixtures have uniform composition throughout, e.g., saltwater.
• Heterogeneous mixtures have non-uniform composition, e.g., sand and water.

Properties of Matter

• Properties of matter can be physical or chemical.
• Physical properties can be observed or measured without changing the substance's composition, e.g., color, density, melting point, boiling point.
• Chemical properties describe a substance's ability to undergo chemical changes or reactions, e.g., flammability, reactivity with acids.
• Intensive properties do not depend on the amount of substance, e.g., temperature, pressure, density.
• Extensive properties depend on the amount of substance, e.g., mass, volume.

Atoms and Molecules

• Atoms are the basic building blocks of matter.
• Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons.
• Protons have a positive charge, electrons have a negative charge, and neutrons have no charge.
• The number of protons determines the element's atomic number.
• Isotopes are atoms of the same element with different numbers of neutrons.
• Molecules are formed when two or more atoms are held together by chemical bonds.
• Chemical formulas represent the number and types of atoms in a molecule, e.g., H2O, CO2.
• Molecular compounds are composed of molecules, while ionic compounds are composed of ions.
• Ions are atoms or molecules that have gained or lost electrons, resulting in a net charge.
• Cations are positively charged ions, formed by losing electrons.
• Anions are negatively charged ions, formed by gaining electrons.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms and molecules.
• Reactants are the substances that undergo change, while products are the substances formed.
• Chemical equations represent chemical reactions using chemical formulas, e.g., 2H2 + O2 → 2H2O.
• Balancing chemical equations ensures that the number of atoms of each element is the same on both sides of the equation.
• Stoichiometry is the study of the quantitative relationships between reactants and products in chemical reactions.
• The mole is the SI unit for the amount of substance, defined as the number of carbon atoms in exactly 12 grams of carbon-12.
• Avogadro's number (6.022 x 10^23) is the number of entities (atoms, molecules, ions) in one mole.

Acid and Bases

• Acids are substances that donate protons (H⁺) or accept electrons.
• Bases are substances that accept protons (H⁺) or donate electrons.
• The pH scale measures the acidity or basicity of a solution.
• pH values range from 0 to 14, with 7 being neutral.
• Acids have pH values less than 7, while bases have pH values greater than 7.
• 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 reactions occur when an acid and a base react to form a salt and water.

Organic Chemistry

• Organic chemistry is the study of carbon-containing compounds.
• Carbon atoms can form stable bonds with other carbon atoms and with other elements, such as hydrogen, oxygen, nitrogen, and halogens.
• Hydrocarbons are compounds composed of only carbon and hydrogen.
• Alkanes are saturated hydrocarbons with single bonds.
• Alkenes are unsaturated hydrocarbons with one or more double bonds.
• Alkynes are unsaturated hydrocarbons with one or more triple bonds.
• Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules, e.g., alcohols (-OH), carboxylic acids (-COOH), amines (-NH2).
• Isomers are molecules with the same molecular formula but different structural arrangements.
• Polymers are large molecules made up of repeating smaller units called monomers.
• Important classes of organic compounds include alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, amines, and amides.