Changes of State January 5, th grade Chapter 4.2

Most Common States of Matter Solid: Definite shape, definite volume Liquid: Indefinite shape, definite volume Gas: Indefinite shape, indefinite volume (depends on pressure) There are other states of matter like plasma, superfluid, strange matter, etc but they’re rare outside of a lab

States of Matter

Pressure Since gas molecules fill the entire container and are constantly moving, they are constantly banging into the sides of their container This is called pressure Pressure can be used for liquids & solids, but then you have to worry about gravity too

Changes of State Which ones do you remember?

Melting Melting: solid  liquid, getting warmer In pure, crystalline substances, melting occurs at only 1 temperature: the melting point. Different substances have different melting points o Water 0°C o Salt (NaCl) 801°C Solid’s molecules were already vibrating: now they vibrate so fast that they break free from other molecules and can float around Add thermal energy to melt something

Freezing Freezing: liquid  solid, getting colder Opposite of melting You can use melting point and freezing point interchangeably because they happen at the same temperature

Vaporization Vaporization: liquid  gas Can be caused by evaporation or boiling Add thermal energy Evaporation: liquid  gas, below the boiling point Only some liquid molecules have enough energy to escape their bonds to other liquid molecules No boiling Boiling: liquid  gas, getting hotter Happens at the boiling point Bubbles of gas form at & below the surface

Condensation Condensation: gas  liquid, getting colder Losing thermal energy The gas molecules don’t have enough energy to be bouncing around, so they become liquid and stick closer together Dew forming Making clouds

Most Common Path SolidLiquidGas

Sublimation Sublimation: solid  gas Sometimes you can go straight from a solid to a gas Dry ice (carbon dioxide, CO 2 )

Graphing Changes of State

How does this work?