Basic Concepts of Chemistry

Matter: Anything that has mass and occupies space. Examples include the sun, sky, water, fire, etc. A key Indian philosopher, Kanad, believed all matter is made of fundamental particles.
Nature of Matter: Chemistry studies the composition, properties, and interactions of matter. Matter can be converted into energy according to E=mc², where E is energy, m is mass, and c is the speed of light.

States of Matter: Matter exists in three states: solid, liquid, and gas.
- Solid: Solids have a definite shape and volume due to strong intermolecular forces.
- Liquid: Liquids have a definite volume but no fixed shape, intermolecular forces are weaker than in solids.
- Gas: Gases have neither a definite shape nor volume, their particles are loosely held.
Interconversion of States: The states of matter can change through heating or cooling (e.g., melting, freezing, evaporation, condensation, sublimation, deposition). These processes are reversible. Pressure and temperature can also affect state changes.

Mixture: Mixtures are substances comprised of two or more components that are physically combined, each component retaining its properties. Mixtures can be homogenous (uniform throughout, like saltwater) or heterogeneous (not uniform, like sand and water).
Pure Substances: Pure substances have a constant composition (unlike mixtures) and can be elements or compounds.
- Elements: Elements are the simplest form of pure matter.
- Compounds: Compounds are combinations of two or more elements that are chemically bonded in a fixed ratio.

Law of Conservation of Mass: The total mass of reactants in a chemical reaction equals the total mass of products. This means mass is neither created nor destroyed.
Law of Definite Proportions: Compounds always contain elements in a fixed proportion by mass. This means the composition is consistent, regardless of the preparation method.
Law of Multiple Proportions: If two elements form more than one compound, the masses of one element that combine with a fixed mass of the other element are in the ratio of small whole numbers.

Elements: An element is the basic building block of matter. Some examples of elements are zinc (Zn), boron (B), sodium (Na), silicon (Si).
Compounds: A compound is made of two or more elements combined in a fixed ratio. The chemical and physical properties of a compound are different from those of the elements that make it.
Chemical Properties: Describes a substance's ability to undergo a chemical change. Examples include acidity, basicity, heat of combustion.
Physical Properties: Properties that can be observed without changing the substance's composition. Examples include color, odor, density.
Units: Standard units are used in measurements for consistency. The international system of units (SI) is globally recognized, including meters (m) for length, kilograms (kg) for mass, seconds (s) for time, and so on.

Numerical values in scientific measurements are often expressed with a certain number, called significant figures, to reflect accuracy and precision. The uncertainty is generally in the last digit.

A technique to convert between units. Conversion factors relate units or quantities to one another to facilitate calculations.

Density refers to mass per unit volume. It measures the compactness of a substance, and can differ between states of matter.
Density can be described as either an absolute density (in relation to mass and volume) and relative density (in relation to the density of water at 4°C).

Atomic mass: The mass of an atom in atomic mass units.
Molar mass: The mass per mole of a substance.
Avogadro's number: The number of atoms or molecules in one mole of a substance.
Molecular mass: The mass of a mole of molecules of the substance.
Mole concept: A mole is a standard unit in chemistry that counts a specific number of particles. (Avogadro's number).
Percentage Yield: Percentage Yield is the actual yield of a reaction divided by the theoretical maximum yield expressed as a percentage.
Sequental Reaction: A reaction in a series; the product of the first step becomes the substrate for the next.
Principle of Atom Conservation: In chemical reactions, the number of atoms for each element remains the same, before, during, and after the reaction.