Overview
This lecture introduces fundamental chemistry concepts, focusing on the definition of matter, states of matter, physical and chemical properties, and the classification of matter into pure substances and mixtures.
What is Chemistry & Matter?
- Chemistry is the study of matter, which is anything that has mass and takes up space (volume).
- Matter can be naturally occurring or synthetic and makes up everything in your environment.
- Chemistry examines what matter is made of, how it behaves, and how it changes (chemical reactions).
States of Matter
- Solid: Definite shape and volume, particles tightly packed in an ordered pattern, vibrate but do not move freely.
- Liquid: Definite volume but takes the shape of its container, particles close together but can slide past each other.
- Gas: No definite shape or volume, particles are far apart and move rapidly, filling the container completely.
- Particles in all states move; only at absolute zero (0 K) are particles motionless.
Physical and Chemical Properties & Changes
- Physical properties: Observed or measured without changing substance identity (color, odor, state, melting point, boiling point, solubility).
- Physical changes: Change in state or appearance without changing composition (melting, boiling, dissolving).
- Chemical properties: Describe a substance’s ability to form new substances (reactivity, flammability, toxicity).
- Chemical changes: Result in a new substance (burning paper, rusting iron, making water from hydrogen and oxygen).
Classification of Matter
- Pure substances: Consist of one type of particle; have a constant composition.
- Cannot be separated by physical processes.
- Can be elements (all atoms identical) or compounds (two or more elements chemically combined, all molecules identical).
- Mixtures: Consist of two or more substances combined physically; composition can vary.
- Can be separated by physical processes (e.g., boiling water from salt).
- Homogeneous mixtures: Uniform throughout (e.g., salt water, black coffee).
- Heterogeneous mixtures: Non-uniform with visible differences (e.g., pizza, salad, orange juice with pulp).
Key Terms & Definitions
- Matter — Anything that has mass and takes up space.
- Solid — State with definite shape and volume; particles closely packed and ordered.
- Liquid — State with definite volume but variable shape; particles close but free to move.
- Gas — State with neither definite shape nor volume; particles far apart and fast-moving.
- Physical property — Observable/measurable characteristic that does not change substance identity.
- Chemical property — Characteristic involving the ability to change into different substances.
- Pure substance — Sample of matter with only one kind of particle and set composition.
- Element — Pure substance with only one type of atom.
- Compound — Pure substance of two or more elements chemically bonded.
- Mixture — Physical blend of two or more substances, variable composition.
- Homogeneous mixture — Mixture uniform throughout.
- Heterogeneous mixture — Mixture with visibly different components.
Action Items / Next Steps
- Review textbook sections 1.1–1.3 for examples and practice problems on classifying matter.
- Prepare to discuss more about mixtures in the next lecture.
- Ask questions if you are confused about distinguishing compounds from mixtures.