3.1 Matter and Energy I CAN: -CONSTRUCT A GRAPH THAT REPRESENTS PHASE CHANGES REPRESENTED BY THE TEMPERATURE OF A SAMPLE VS. THE TIME IT HAS BEEN HEATED. -DIFFERENTIATE BETWEEN A PHASE CHANGE AND A TEMPERATURE CHANGE (OBSERVING THE PATTERN ON THE GRAPH). -EXPLAIN WHY IT IS A PHASE OR TEMPERATURE CHANGE. -RECOGNIZE THAT DURING THE PHASE CHANGE THE ENERGY GOES INTO CHANGING THE POSITION OF THE PARTICLES (WHICH IS POTENTIAL ENERGY) INSTEAD OF CHANGING THE KINETIC ENERGY (WHICH IS THE TEMPERATURE). -RECALL THAT THE KINETIC ENERGY OF THE PARTICLES IS USED TO BREAK THE ATTRACTIVE FORCES BETWEEN THE PARTICLES. -RECOGNIZE THAT A SUBSTANCE MELTS OR BOILS DEPENDING ON THE KINETIC ENERGY AS PART OF THE PHASE CHANGE (AND CONVERSELY WHEN COOLING). -EVALUATE THE DIRECTION OF ENERGY FLOW AND IDENTIFY REACTIONS AS ENDOTHERMIC VS. EXOTHERMIC. -RELATE THAT IN GENERAL THE SPACE BETWEEN THE PARTICLES DETERMINES THE PHASE OF THE MATTER (UNDERSTANDING WATER IS AN EXCEPTION).

Fire at Lima Factory 10/2014

Kinetic Theory All matter is made of atoms and molecules that act like tiny particles The particles are always in motion. (Higher temp=faster movement) At same temp, heavier particles move slower the lighter particles.

Solids have definite shape and volume Solids do not need containers Particles cannot change position Two categories ◦crystalline-iron, diamonds, ice ◦amorphous-rubber, wax, gum (can be compressed)

Liquids can change shape, not volume! Particles can slid past each other. Move fast enough to overcome force of attraction between them. (flow freely) Take shape of container Surface tension: force acting on the particles at the surface of a liquid that causes liquid to form spherical drops.

Gases are free to spread in all directions Gas expands to fill space He can travel at 1200 m/s One cylinder of helium can fill 700 balloons, but the cylinder is to the volume of 5 inflated balloons. Gases change shape and volume

Plasma is the most commons state of matter. 99% of all known matter in the universe (sun/stars) is plasma. Does not have definite shape Plasma: state of matter that starts as gas and then becomes ionized (turn atoms into ions) Similar to gas, but conducts electricity. Ex on earth: lightning, fires, northern lights (electric current through gas)

Energy’s Role Energy: the capacity to do work Ex: candles for light, batteries, electricity, food we eat, chem. Reactions that release heat. Particles in motion (solid, liquid, gas) have kinetic energy. Thermal Energy: the total kinetic energy of the particles that make up an object. Higher temper  faster moving particles  more kinetic energy  more thermal energy. May also depend on number of particles. In the previous slide, which picture shows most thermal energy?

How do we measure temperature? Hot or cold? Temp is the measure of how the average kinetic energy of the particles in an object. Temp of a substance is not determined by amount. Total kinetic energy is determined by amount. Tea pot example.

Energy and Changes of State Water can be ice, liquid, gas. Still H20 Energy is different in each. Temperature is a measure of energy Transfer of energy known as heat causes change of state.

Some changes of state require energy (heating up) Melting, requires energy (heating up)= endothermic change. Melting point: water 0 degrees C, Table salt is 801 degrees C Evaporation: The change of a substance from a liquid to gas Boiling Point: water is 100 degrees C, Mercury is 357 degrees C. Reversing the process is exothermic… Think about the energy transferring when you sweat. Sublimation: the process in which a solid changes directly into gas. Common in dry ice, or ice left in freezer for a long time.

Energy is released in some changes of state (cooling down) Condensation: the change of a substance from a gas to a liquid ◦Energy is released from water to its surroundings. ◦Condensation point: temp at which gas becomes liquid. ◦Freezing point: temp in which liquid becomes solid. Condensation and freezing are both exothermic reactions because energy is released.

Thanks Aja’s boyfriend… <3

Conservation of Mass and Energy In both physical and Chemical changes, total mass of matter stays the same before and after the change. Law of conservation of mass: mass can neither be created nor destroyed. ◦Does burning a match lose mass? ◦There is mass in oxygen. (ash, smoke, and gases= original mass) Law of conservation of energy: energy can be converted to different forms, but never created nor destroyed. ◦Burning gas produces energy need to move car.