• change in size, shape, or phase (solid, liquid, gas)
• does not change what the substance is
• is often reversible
• examples: dissolving, crushing, cutting, melting, freezing, evaporating
• Chemical Change - a change in which one or more substances combine or break apart to form new substances
• changes the chemical makeup of the substance
• often accompanied by release of a gas, color change, odor, release of heat
• usually not reversible
• examples: burning, rusting, baking, digestion, photosynthesis
• Conservation of Mass - matter cannot be created or destroyed through chemical or physical changes
• In a chemical reaction, all atoms present at the start of a reaction are present at the end
• ex. Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2
• Solid
• has a definite shape and a definite volume
• particles are packed tightly together in a fixed position; can vibrate slightly
• crystalline solids have particles arranged in a regular, repeating pattern
• melt at a specific temperature
• examples: sugar, salt, snow, quartz