Basic Chemistry Concepts

Atomic Structure

• Atoms are the building blocks of matter
• Consist of:
  • Protons (positive charge) in the nucleus (center)
  • Neutrons (no charge) in the nucleus
  • Electrons (negative charge) orbiting the nucleus

Properties of Matter

• Mass: a measure of the amount of matter in an object
• Volume: the amount of space occupied by an object
• Density: mass per unit volume of a substance

States of Matter

• Solid: particles are closely packed and have a fixed shape and volume
• Liquid: particles are close together but can move past each other, taking the shape of their container
• Gas: particles are widely spaced and can move freely, expanding to fill their container
• Plasma: high-energy state where atoms are ionized, often found in stars and lightning

Physical and Chemical Changes

• Physical Change: a change in the state of matter, but not in its chemical composition (e.g., melting ice)
• Chemical Change: a change in the chemical composition of a substance, resulting in a new substance (e.g., rusting iron)

Mixtures and Substances

• Mixture: a physical combination of two or more substances, where each maintains its chemical properties
• Substance: a pure form of matter with a fixed chemical composition (e.g., water, iron)

Particle Theory

• Matter is composed of tiny particles called atoms and molecules
• Particles are in constant motion, with kinetic energy increasing with temperature
• Particles have space between them, even in solids