Matter and the Kinetic Molecular Theory

Matter: Defined as anything that has mass and occupies space, making up everything in the universe.
Particles: Matter is composed of atoms; atoms typically combine to form molecules.
Intermolecular Space: The empty space between molecules within a substance.
Intermolecular Force: The attractive force that holds molecules together. As space between molecules decreases, the force of attraction increases.

Matter Composition: Composed of very small particles called molecules which are identical for a given substance.
Random Motion: Molecules are in a constant state of random motion and possess kinetic energy.
Temperature Dependency: The kinetic energy of molecules depends on temperature. Higher temperatures cause faster movement and greater kinetic energy.
Molecular Collisions: Molecules collide with each other and the walls of their container, exerting pressure.

Cohesive Force: Attractive force between molecules of the same kind (e.g., water molecules sticking together to form a dew drop).
Adhesive Force: Attractive force between molecules of different kinds (e.g., water drops clinging to glassware).

Solids: Molecules are tightly packed with very small intermolecular spaces and very strong intermolecular forces. Molecules only vibrate about fixed positions; they have definite shape, definite volume, and are rigid.
Liquids: Molecules are less tightly packed than in solids with larger intermolecular spaces and weaker forces. They have a definite volume but no definite shape and are able to flow.
Gases: Molecules are far apart with very large intermolecular spaces and negligible forces. They have no definite shape or volume and possess the maximum kinetic energy.
Plasma: A fourth state of matter consisting of free electrons and ions, occurring at very high temperatures in the sun, stars, and neon bulbs.

Melting: Process where a solid changes to a liquid as molecules gain kinetic energy and intermolecular spaces increase ( $Solid \rightarrow Liquid$ ).
Freezing (Solidification): Process where a liquid loses energy and molecules come closer to form a solid ( $Liquid \rightarrow Solid$ ).
Boiling (Vaporization): Rapid conversion of a liquid to a gas at a particular temperature throughout the liquid ( $Liquid \rightarrow Gas$ ).
Evaporation: Surface phenomenon where molecules with higher kinetic energy escape into the space above the liquid as vapour ( $Gas$ ).
Condensation: Process of a gas changing into a liquid upon cooling ( $Gas \rightarrow Liquid$ ).

Definition: Antoine Lavoisier stated that matter can neither be created nor destroyed during a chemical reaction.
Principle: The total mass of the products always equals the total mass of the reactants.
Application in Physical Changes: Boiling $10\,g$ of water yields $10\,g$ of steam; cooling it yields $10\,g$ of ice.
Application in Chemical Changes: In the reaction $\text{magnesium} + \text{oxygen} \rightarrow \text{magnesium oxide}$ , the total mass before and after remains identical.

Quotes: Antoine Lavoisier famously stated, "Nothing is lost, nothing is created, everything is transformed."
Logical Thinking: It is much easier to compress gases by applying pressure than liquids or solids because of the large intermolecular spaces in gases.
Critical Thinking: During evaporation, no bubbles are seen, whereas during boiling, bubbles arise from all over the liquid, indicating boiling is a bulk phenomenon and evaporation is a surface phenomenon.
Activity to Verify Law of Conservation of Mass: Mixing $10\,mL$ of barium chloride solution with $10\,mL$ of sodium sulphate solution results in a chemical reaction ( $\text{barium chloride} + \text{sodium sulphate} \rightarrow \text{barium sulphate (white precipitate)} + \text{sodium chloride}$ ) where the mass of the conical flask remains unchanged.