Overview
This lecture introduces basic chemistry concepts essential for understanding future biology topics, focusing on matter, states, and chemical reactions.
Matter and Its Properties
- Chemistry studies matter and the changes it undergoes, known as chemical reactions.
- Matter is anything with mass (amount of substance) and volume (amount of space occupied).
- Mass differs from weight; weight includes gravitational pull, but mass does not.
- Volume is measured as the space an object occupies (e.g., length × width × height).
States of Matter
- Three states of matter: solid, liquid, and gas.
- Solids have definite shape and volume.
- Liquids have indefinite shape but definite volume, taking the shape of their container.
- Gases have indefinite shape and volume, also filling their container.
- Volume can be measured for all states, but shape measurement is only meaningful for solids.
Phase Changes
- Solid to liquid transition is called melting.
- Liquid to solid transition is called freezing.
- Liquid to gas is evaporation.
- Solid to gas is sublimation.
- Gas to solid or gas to liquid transitions are called condensation.
- The composition of the substance does not change during phase changes, only its physical state.
Chemical Reactions and Equations
- Chemical reactions involve substances changing into different substances (chemical change, not just physical).
- In equations, reactants are placed on the left side of the arrow and products on the right.
- The arrow in a chemical equation usually means "yields."
- Number of reactants or products can vary from one to several.
- Knowing which substances are reactants or products is important for understanding biological processes.
Key Terms & Definitions
- Chemistry — study of matter and its changes.
- Matter — anything with mass and volume.
- Mass — amount of substance in an object.
- Weight — gravitational pull on mass.
- Volume — amount of space an object occupies.
- Solid — state with definite shape and volume.
- Liquid — state with definite volume, variable shape.
- Gas — state with variable shape and volume.
- Melting — solid to liquid transition.
- Freezing — liquid to solid transition.
- Evaporation — liquid to gas transition.
- Sublimation — solid to gas transition.
- Condensation — gas to liquid or gas to solid transition.
- Chemical reaction — process where substances change into other substances.
- Reactant — starting material in a chemical reaction, left of the arrow.
- Product — substance formed in a chemical reaction, right of the arrow.
Action Items / Next Steps
- Review which substances are reactants and which are products in major biological reactions (e.g., photosynthesis, cellular respiration).
- Prepare for potential test questions on chemical equations and states of matter.