3.1 Matter and Energy Kinetic Theory of Matter: – All matter is made of atoms – Atoms always in motion; hotter = faster, faster = hotter – Heavier particles move slower than lighter at the same temperature So thermal energy (temperature) is a measure of kinetic energy (motion) of molecules – Higher temp…more energy…move faster – Lower temp…less energy…move slower

States of matter Solid: particles close together (still move … vibrate) – definite Shape – definite Volume Liquid : particles are close but move freely … slide past each other – no definite Shape (container) – definite Volume Gas: particles are far apart … take available space – no definite Shape – no definite Volume Plasma: electrons free from nucleus (ionized); like a gas with an electric charge

States of matter Phase changes: going from 1 state to another … a physical change, does not change the substance … involves energy – Exothermic: heat leaves (heat ex its) condensation: (gas to liquid) solidification: (liquid to solid, also called freezing) deposition: (gas to solid) – Endothermic: heat enters (heat goes in to it) melt: (solid to liquid) evaporate: (liquid to gas) sublimate: (solid to gas)

States of matter

Conservation of… Law of Conservation of Mass: – mass can not be created or destroyed. It only changes form. You have the same mass before a reaction as you would after. Law of Conservation of Energy: – energy can not be created or destroyed. It only changes form. You have the same energy before a reaction as you would after.

Phase diagrams Shows what happens as add heat. Adding energy doesn’t always change the temperature! When not changing phase: temperature goes up as molecules move faster (or slower if cooling) During phase change: temperature doesn’t change because energy is causing molecules to move farther apart. (or closer together if cooling)

Phase diagrams

Pressure Temperature is not the only way to change state of matter. Pressure can also change state of matter by pressing molecules closer or allowing them to move farther apart. As pressure goes up, gas  liquid  solid As pressure goes down, solid  liquid  gas

Phase diagrams

show combinations of temperature and pressures to achieve different phases. Triple point: temperature and pressure at which the substance can be a solid, liquid and gas all at once and stay that way. For water this is 0.01 °C and a pressure of atm (1 atm = air pressure at sea level. Lines on graph represent phase changes (as either temperature or pressure change)