Physical Change Phases of Matter Waters Phases Water

Physical Change Phases of Matter

Waters Phases: “Water” “Ice” “Vapor” They might seem completely different… But are they really? ***You learned about the details of phases themselves in 7 th grade. We are going to focus on WHY and HOW they change.

Phases & States of Matter • Today’s two big points: – All phases are dependant upon the amount of thermal (heat) energy the substance – And how the energy affects the bonds between molecules in the substance.

Property you need to know: If a substance is a solid, liquid, or gas at a certain temperature: That is a Property of that substance! EX: Water is a good example since it is so simple! <0 degrees Celsius = Solid (if you stuck a thermometer in a solid piece of “ice” what would be a temperature you would expect? ) >0 degrees Celsius = Liquid (if you stuck a thermometer in a glass of liquid water what would be a temperature you would expect? ) >100 degrees Celsius = Gas Water is pretty much the ONLY substance that changes phase at these temperatures. For example: Nitrogen will still be a gas at -196 degrees Celsius!!! Nitrogen will MELT at -210 degrees Celsius (-346 F)!!! ***All substances change phase at a certain temperature unique for that substance. “Hot” and “cold” don’t matter…

Energy of the Phases: Q: What is the ONLY real difference between each phase? A: The amount of energy the molecules have!

Solids • Very little energy – Not enough energy to break the bonds between molecules • Strong Bonds – Definite Shape (doesn’t change) – Definite Volume (can measure it) • Molecules very close together This picture shows what the atoms in a solid are doing (if we could see them)

Liquids • “Medium” Energy – Some bonds get broken – but they keep reforming. • “Medium” Bond Strength – No Definite Shape (Takes shape of “container”) – Definite Volume (Can measure it) • Not as tightly packed together – Can move around some (“flow”) This picture shows what the atoms in a liquid are doing (if we could see them)

Gases • “High” amount of Energy – Enough energy to break the bonds • “Weak” Bond Strength – No Definite Shape (can’t see it) – No Definite Volume (difficult to measure) • Very spread out – Moving freely through container This picture shows what the atoms in a gas are doing (if we could see them)

Energy of the Phases Review: • Solid: Q: Would you describe this as having a high, medium or low amount of energy? • Liquid: Q: Would you describe this as having a high, medium or low amount of energy? • Gas: Q: Would you describe this as having a high, medium or low amount of energy? Q: What is the ONLY real difference between each phase? A: The amount of energy the molecules have!

Changing from Phase to Phase Review: Water is a great example because we are all so familiar with it! Melting Solid Freezing Vaporizing Liquid Q: When What As a substance do wewe change have experiences to thedo phase, to make a a phase have we change, change made awhat to new a are new substance? the phase? processes called? A: NO! IT IS STILL WATER (H O)! 2 Condensing Gas A: Increase or decrease the energy A: Melting, Freezing, Vaporizing (Boil Change! ***No change in the substance = Physical of the. Evap. ), molecules in the substance! and Condensing