*** ENERGY AND MATTER PHASES ******

Key ideas to remember:

USUALLY, matter cannot be created or destroyed. But matter can give off energy during physical or chemical changes, and some chemical and physical changes take in energy.

With lots of energy, matter can be changed to pure energy, and energy to matter. This is the famous E equals M C squared statement.

1) When a solid is changed into a liquid, how is it usually done?

2) When a solid is changed to a liquid does it take in heat or give off heat?

Take in heat

3) Is matter created or destroyed when an ice cube melts to water? Y/N

NO

4) When a liquid changes to a gas , how is it usually done?

5) When a liquid is changed to a gas does it take in heat or give off heat? Choose One

take in heat

6) Is matter created or destroyed when a liquid changes to a gas? Y/N

NO

7) Think about the bonds between molecules. Which phase has bonds that are hardest to break? Which would need the most energy to break the bonds?

Solid, Solid

8) When a solid breaks its bonds and changes to a liquid does it take

in (need) heat or give off heat?

Take in Hear

9) When a liquid forms bonds and changes to a solid does it take in (need) heat or give off heat? choose one Give off heat (take in cold)

10) When a liquid breaks its bonds and changes to a gas, does it take in (need) heat or give off heat? choose one  Take in heat
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11) When sweat (a liquid) evaporates and changes to a gas is energy given off or taken in? choose one taken in (from skin)

12) When steam (a gas) condenses and changes to water (a liquid), is energy given off or taken in?  choose one Why would this explain why steam burns so badly when it condenses? Given off, steam burns as gas molecules give off heat to your skin when they form bonds.

13) List the three phase CHANGES that would give off heat:

Gasà Liquid, (Condensation) , Liquid à Solid (Freezing/Fusion), Gas à Solid (Sublimation)

14) List the three phase CHANGES that would take in heat:

Solid à Liquid (Melting), Liquid à Gas (Vaporization), Solid à Gas (Sublimation)

15) Which has the most heat energy stored in it: SOLIDS, LIQUIDS, OR GASES?

Gas

16) Which has the least heat energy stored in it: SOLIDS, LIQUIDS, OR GASES?

Solid

17) Which has more heat energy stored in it, an ice cube at 32 degrees Fahrenheit or a glass of water at 32 degrees Fahrenheit? WHY?

Water, it took in heat to break bonds

18) When an ice cubes melts, it takes heat to do so. Where does the heat usually come from?  The surroundings (air, etc…)

19) When evaporation takes place it needs heat to do so. Where does the heat usually come from? The surroundings (air, etc… )

20)Do you think that evaporation (liquid to a gas) is a cooling or a heating process for its surroundings and why?  A cooling process ( takes in heat from the surroundings)

21) Does moving air speed up evaporation or slow it down? choose one

Speeds it up

22) How might this explain why you feel cold coming out of a shower, or why you blow on soup to cool it off, or why there is such a thing as a wind chill factor?

Air moving speeds up evaporation of the sweat on your skin, increasing the phase change from liquid to gas, taking in heat from your skin.

23) What phase changes do you think might help refrigerators work and why?

Liquid to gas in front taking in heat from food, then compressed back to liquid in back giving off lots of heat.

24) What is the difference between evaporation and boiling?

Evaporation happens at the surface, boiling at the bottom.