Overview
This lecture introduces types of matter, their physical states, types of changes, and classification into pure substances and mixtures.
Phases of Matter
- Matter is anything with mass that occupies space.
- There are three phases of matter: solid, liquid, and gas.
- Solids have fixed shape and volume; their particles are touching and do not move.
- Liquids have fixed volume but not shape; particles are touching and move fluidly.
- Gases have neither fixed volume nor shape; particles are far apart and move freely.
Physical and Chemical Changes
- A physical change does not alter the chemical composition of a substance.
- Phase changes (like melting ice) are always physical changes.
- A chemical change involves breaking and forming of chemical bonds to create new substances.
- Combining hydrogen and oxygen gases to form water is an example of a chemical change.
Classification of Matter
- A pure substance cannot be separated into other materials by physical means.
- Water is a compound because it consists of two elements: hydrogen and oxygen.
- An element cannot be broken down by physical or chemical means.
- Mixtures consist of two or more pure substances and can be separated by physical processes.
- Mixtures can be homogeneous (uniform throughout, e.g., sugar in water) or heterogeneous (non-uniform, e.g., oil and water).
Key Terms & Definitions
- Solid — Phase with fixed shape and volume; particles are tightly packed and immobile.
- Liquid — Phase with fixed volume but variable shape; particles are mobile but touching.
- Gas — Phase with no fixed shape or volume; particles are far apart and move freely.
- Physical Change — Change in state or appearance without altering chemical composition.
- Chemical Change — Change that forms new substances via breaking/forming chemical bonds.
- Pure Substance — Material that can't be separated by physical means (element or compound).
- Element — Pure substance made of one type of atom; cannot be chemically broken down.
- Compound — Pure substance made of two or more types of atoms chemically bonded.
- Mixture — Physical combination of two or more pure substances; can be separated physically.
- Homogeneous Mixture — Mixture with uniform composition throughout.
- Heterogeneous Mixture — Mixture with non-uniform composition.
Action Items / Next Steps
- Review definitions of physical and chemical changes.
- Practice classifying examples of matter as pure substances, compounds, or mixtures.