Vocabulary
the way molecules move in a substance relative to one another
freedom of movement
why do solids keep their shape
molecules move only in place
what does temperature measure
average kinetic energy of molecules
What happens when KE is too low compared to molecular attraction?
molecules pull together (condensation or freezing)
puddle disappears on a hot day, what happened?
evaporation: the liquid molecules gained energy from the sun, moved apart and escaped as gas
energy of motion
kinetic energy
why don't gases have a fixed shape
molecules move apart freely
when energy is transferred in, what happens to molecules
move faster, more FOM
Which requires more energy to evaporate: water or methane? Explain.
Water, because it has stronger molecular attraction
helium balloon shrinks on a cold day, why?
molecules move slower and closer together as they lose kinetic energy, taking up less volume, the balloon shrinks
noticeably different form of the same substance
phase
use molecular behavior to explain why liquids flow and solids do not
liquid molecules move around each other (but not away), but solids are locked in place
why didn't titan's lake freeze in the summer
energy transfer increases KE, for freezing KE must decrease
Why did it take 5+ years for Titan's methane lake to evaporate?
molecular attraction had to be overcome, and it took time for enough to be transferred
spoon in hot tea warms after a few minutes, what happens to the molecules in the spoon?
energy transfers from tea to the spoon, molecules in spoon speed up
pull between two molecules
molecular attraction
when fall returns, Titan's lake will refill with liquid methane, use your knowledge of phase change to explain how this will happen
the temps will get cold again causing the methane gas in the air lose KE and FOM, condense and fall back into the lake (methane rain)
If Titan's summer was only 3 months, would the lake have evaporated
no, there would not have been enough KE transferred into the methane to over come the molecular attraction and evaporate
if a molecule has weak molecular attraction, how would that affect the temperature at which the substance freezes
the substance would freeze at a lower temp because the molecules have need more energy transferred out in order to slow down and pull together as a solid
water condenses on a cold can, water evaporates from a pot on the stove
which involves energy input, whcih involves releases energy
condensation: energy release
evaporation: energy input
average kinetic energy of the molecules in a substance
temperature
How do flash floods occur in the slot canyons of the desert?
water vapor rises due to hot temps, but when they reach higher altitudes they cool and condense, falling back into the canyons as rain
why does an ice pop thaw outside of the freezer, explain the KE
energy from the air transfers into the ice pop causing the molecules to speed up and gain FOM, this overcomes molecular attraction and the ice pop melts
when gas pressure increases, what affect does this have on molecular attraction and condensation?
boyle's law states that as pressure incr, volume decr, making molecules closer together. so, molecular attraction becomes more effective, making condensation more likely--molecules pulled together into a liquid
You open a soda left in a hot car, and liquid sprays out. What phase change happened and why?
Heat increased kinetic energy, causing dissolved gas to escape as bubbles (gas expansion)