Matter & Energy

If you heat something, what’s happening on the Atomic Level?

• Atoms, no matter what the temperature or state (solid, liquid, gas) are always moving.

• Movement only stops at Absolute Zero (0Kelvin or -273 Celsius)

• When you cook food, the energy from the stove is transferred to the food.

• The food particles begin to move much faster (and may spread through the air in the kitchen – now you can smell the food!)

The Kinetic Theory explains why this happens.

• All matter is made of atoms and molecules that act like tiny particles

• These tiny particles are always in motion. The higher the temperature, the faster the particles move.

• At the same temperature, heavier particles move slower than lighter particles

Solids

• On the atomic level, look like this:

• The particles are closely packed but they still vibrate

• Have a definite shape and volume– Ice cubes take the shape of

the ice cube tray

Liquids

• On the atomic level, liquids look like this:

• The particles of a liquid are close together but they can slide past each other.

• Have a definite volume, but they can change shape.– Water in a cup will keep the

same volume but change shape if poured into another object.

Gases

• On the atomic level, look like this:

• Gas particles are in a constant state of motion and rarely stick together.

• Able to change both volume and shape.– The amount of empty space

between particles changes, so the volume is able to change.

Click on the Links to View Each State on the Atomic Level

• http://www.hbschool.com/activity/states_of_matter/

• http://www.dac.neu.edu/physics/b.maheswaran/phy1121/data/ch04/anim/anim0402.htm

• http://www.visionlearning.com/library/module_viewer.php?mid=120&l=&c3

Some Changes Require Energy

• If a substance goes from a state of little motion to a state of more atomic motion, the change REQUIRES energy.

• Evaporation: liquid to gas

• Sublimation: solid to gas

• Melting: solid to liquid

Some Changes Release Energy

• If a substance goes from a state of high atomic motion to a state of less atomic motion, the change RELEASES energy.

• Condensation: Gas to Liquid• Freezing: Liquid to Solid

Temperature Change vs. Change of State

• Let’s do a lab to see how the temperature changes when the phase changes!

• Conclusion of the Lab:– When a substance loses or gains energy, either its

temperature changes or its state changes.– The Temperature of a substance does NOT change

during a change of state.

Did Your Graph Look Like This?

I'm melting, I'm mellltinnggg.

-The Wicked Witch

Law of Conservation of Mass & Energy

• Mass cannot be created or destroyed.

• Matter may change, but the total mass always stays the same. – If you light a match, the match looks like

it loses mass– The mass is still the same – some of it

may be carbon dioxide & other gases

• Energy cannot be created or destroyed.

• Energy CAN change forms.– Energy stored in gasoline turns into

energy to move the car

Let’s See if Mass Really is Conserved!