• "What is in common between chocolate chip cookie dough and chocolate chip cookies? Sugar, Flour, baking soda , butter, chocolate chips
• "What is the difference?" It's turned hard, brown.
• "Can we change it back?" no it has gone chemical changes

• "What are some examples that you can think of where substances change from one shape form or identity?" Wood to a toothpick or base ball bat. Water to ice or steam

Types of changes: As we talked about before there are two types of changes Physical changes and chemical changes.

• "What are the differences between the two?"

Physical: change of shape or form, but not what it is.

Chemical: change of it from one substance to another with different properties.

• These changes occur because the energy in the substances is changing.
• Energy comes in different forms.
• Thermal Energy: the temperature of the substance, how fast the particles in the substance are moving.
• Chemical Energy: the energy found in the chemical bonds holding matter together.
• Change: Change occurs anytime energy is added to or taken away from a substance.
• Heating and Cooling: As we have seen many changes occur from the adding and removing of thermal energy. By removing thermal energy substances cool and can freeze into a solid. By adding thermal energy they can melt or turn into a gas.
• The energy of the system remains the same, it is never gained or lost it is transferred to other things. This is know as the "Law of Conservation of Energy"

ADD: Use temperature probes and set-up the computer to take the measurements during class while the class records observations

• "What happens to the temperature of the cup as we melt the ice"? It stays the same
• "Why doesn't it go up where is the energy going"? Into the ice to melt it.
• "What is that energy being used for if it isn't being lost?" It is being used to break the crystal bonds and give energy to the molecules to form water.
• "Have any of you ever unpacked after a move or trip?"
• "Does this take a lot of time and effort, energy?" Energy was being used to move the particles and change their arrangement, unpacking them and letting them flow away.

• "What is the energy doing in the following examples?"
• Melting: Solid to a liquid, Many substances melt at a melting point, the temperature at which the attraction between particles are broken. First molecules vibrate then, then at 0'c the molecules break free. The temperature quits increasing as the energy is being used to free the particles.
• Freezing: Liquid changes to a solid: Energy is being taken by the cold air in the freezer to keep those air particle flying around. Hot always moves to cold to give energy to the colder particles. First the molecules move more and more slowly. Eventually they move so slow that bonds between molecules start to form in regular patterns called crystals. As energy is being lost to the cold air of the freezer the temperature remains the same. Once all the molecules have frozen then the temperature continues to decrease as they vibrate more and more slowly.

• Vaporization: Liquid changing to a vapor. this occurs as particles get enough energy to escape the liquid and become a gas.
• Evaporation: One type of Vaporization that occurs at the surface of a liquid. This occurs at fairly low temps such as a puddle that evaporates in the sun. Energy from the air is given to particles at the surface of a liquid this causes them to escape into the air. That's why you cool down as you sweat. Your body heat is enough to launch the water molecule from your skin, they use your heat to escape and take it with them cooling you.
• Boiling: Another form of vaporization where there is enough energy in a liquid that the molecules turn into gases in the liquid creating bubbles. This takes a high temp, since all the molecules are near the boiling point. The liquid will stay at the boiling point temperature until all of the molecules have escaped as a gas.
• Air Pressure: "What is pressure?" It is the force of a gas on an area. The air around us creates a pressure on us at all times miles of gas push down on us daily. As you go higher in the air the pressure decreases because there are less air particles. Pressure pushes down on liquids making it harder for particles to escape. In areas of low pressure liquids boil at low temps because the air isn't pushing down on it.
• Condensation: Gas to a liquid, As a gas loses thermal energy the bonds between molecules start to attract. Molecules clump together forming liquid droplets. Such as on the side of a glass or a cloud. Breathing on a mirror, warn air particles in your mouth hit the cool glass pane and condense giving their energy to the particles in the pane.

• Sublimation: Solid to a gas. Energy is given to a solid at such a rate that it turns into a gas. Throwing ice into a blast furnace will turn to steam. Ice cubes in a freezer seem to shrink and get smaller. Dry ice CO2 seems to smoke.