Unit 3-2 Matter and Phase Changes Mr. Coffey

Remember matter? Matter is defined as anything that has mass and takes up space (has volume!). Matter is made up of molecules that can move Molecules are groupings of atoms; the small pieces that make stuff up! The molecules in EVERYTHING are moving – even if we can’t see or feel them moving!

Solids Solids have a definite volume and shape That means that if left alone, their shape won’t change Ex: the size & shape of a building doesn’t change The molecules are packed closely together

Amorphous Solids These are solids that DO NOT keep their definite shape. Wax, Tar, & Glass

Liquids Have a definite volume and fill a definite amount of space – but their shape will change based upon their container! If you pour a liquid from one container to another it will change its shape but still be the same amount!

Gasses They have no definite shape or volume They will completely fill whatever container they are in which causes volume to increase & decrease. The molecules can spread out or be pushed together Gas molecules are constantly hitting each other & colliding with the wall of their containers

Plasma Matter existing at extremely high temperatures; it is very rare on earth Found mainly in stars – very high energy sometimes causes chemical bonds to break. Neon lights are plasma! Noble gases are excited by the electricity that passes through creating plasma Plasma TVs are PLASMA!

YES YES NO YES NO NO Sum it up! State of Matter Definite VOLUME?? Definite SHAPE?? SOLID LIQUID GAS YES YES NO YES NO NO

Arrangement of Particles

How do phases/states CHANGE? Substances can change their state when thermal energy is added or subtracted. Thermal Energy is how much energy something has because of how much it’s molecules move. When we heat things up the molecules move faster! Because the molecules move faster, they move apart!

Continued…. Note: heat will always move from WARM to COLD When substances are heated, the attractive forces weaken…..so the molecules move AWAY from each other!

+ or – Thermal Energy If we add or subtract thermal energy, we can force a phase change to happen! Cooling = taking away energy Heating = adding energy Temperature is the measure of the amount of heat in an object, remember there is no such thing as cold….only LESS HEAT Temperature is the measure of how fast molecules move – average KINETIC ENERGY!

The Molecules Molecules in a solid are packed close together, as they heat up they move apart

Phase Changes Phase changes are physical changes. Changing states of matter: SOLID LIQUID GAS

Y F D E Gas TEMPERATURE (°C) B C Liquid Solid A X HEAT ENERGY

A B C D E F A B Yes D E No B C No E F Yes C D Yes Is the temperature changing from: HEAT ENERGY TEMPERATURE (°C) A B C D E F A B Yes D E No B C No E F Yes C D Yes

What is happening during the steps where the temperature is constant (not changing)? PHASE CHANGES!

From left to right (absorbing energy) HEAT ENERGY TEMPERATURE (°C) Solid Liquid Gas A F From left to right (absorbing energy) B C D E MELTING B C

From left to right (absorbing energy) HEAT ENERGY TEMPERATURE (°C) Solid Liquid Gas A F B C D E VAPORIZATION D E

From right to left (losing energy) HEAT ENERGY TEMPERATURE (°C) Solid Liquid Gas A F From right to left (losing energy) B C D E Freezing B C

From right to left (losing energy) HEAT ENERGY TEMPERATURE (°C) Solid Liquid Gas A F From right to left (losing energy) B C D E Condensation D E

If this diagram is for water (H20)… Y HEAT ENERGY TEMPERATURE (°C) Solid Liquid Gas A F B C D E 0°C 100°C

All together!

Let’s Review! Solid Liquid Gas Freezing Condensation Melting Vaporization

Deposition Solid Liquid Gas Sublimation

Terms to know Phase Change Definition Thermal Energy Melting Add Solid  Liquid Add Freezing Liquid  Solid Subtract Vaporization Liquid  Gas Evaporation Boiling Condensation Gas  Liquid Sublimation Solid  Gas

What we all want to know! Question: For water, why does the temperature remain unchanged at 0°C when it is melting (solid to a liquid)? Answer: In order to go from a solid to a liquid, the molecules use the HEAT ENERGY to change the arrangement of particles from: The temperature does not increase because the heat is being used for this!

What we all want to know! Question: For water, why does the temperature remain unchanged at 0°C when it is freezing (liquid to a solid)? Answer: In order to go from a liquid to a solid, the molecules release the HEAT ENERGY as the arrangement becomes more rigid: The temperature does not decrease because the heat is being released for this!

The same is true for vaporization and for condensation!

Some general thoughts…. As you move from left to right, the heat energy increases over time. As you move from right to left, the heat energy decreases (is lost to the environment, or atmosphere) over time. In general, the greater the heat energy, the greater the temperature, and the lesser the heat energy, the lesser the temperature.

Phase Changes As you go from left to right, the heat energy increases. During phase changes (melting and vaporization), the heat energy is not used to raise the temperature. Instead of raising the temperature, the heat energy is used to provide the molecules with more energy to move around.

Phase Changes Continued As you move from right to left, the heat energy decreases. During phase changes (condensation and freezing), the loss of heat energy is not seen on a thermometer (no decrease in temperature). Instead, the heat energy is lost because the molecules are becoming more rigid, and they do not need the extra energy for particles to move around.