Unit Questions
What happened to the LIQUID in Titan's lake?
it evaporated
a GROUP of atoms JOINED together in a particular WAY
Molecule
What is the phase change that occurs when a solid transitions to a liquid?
melting
How do the molecules in the solid move before the phase change?
Moving in place
What happens to molecules when their kinetic energy decreases?
they slow down and get closer.
a noticeably DIFFERENT form or state of the same SUBSTANCE
Phase
From a solid to a liquid, was energy transferred in or out of the system?
energy transferred in
How do the molecules in the liquid move?
around each other
Why didn’t the liquid methane CHANGE phase BEFORE 2007?
A phase CHANGE occurs when the kinetic energy INCREASES enough to overcome the attraction BETWEEN molecules
the ENERGY that an object has because it is MOVING
Kinetic Energy
Gas to a Liquid: Was energy transferred in or out of the substance?
Energy transferred out
Prior to a phase change the molecules in a substance were moving away from each other. After the phase change the molecules are moving around each other.
What phase change occurred?
condensation
What could cause LIQUID methane to change PHASE?
An increase in temperature and kinetic energy
the way MOLECULES in a substance MOVE around RELATIVE to each other.
Freedom Of Movement
Workers find two substances. One is a toxic chemical. The other is a safe chemical. Both chemicals are liquids at room temperature. As a test, the workers transfer the same amount of energy out of the two containers and find that only the toxic chemical changes phase. How is the toxic chemical different from the safe chemical?
The toxic chemical has a . . . .
stronger attraction between its molecules than the safe chemical. Its molecules now move in place.
Refrigerators are able to transfer energy out of a substance. At first, the substance is a gas. The refrigerator changes the phase of the substance by transferring energy out of it. How does this change affect the substance’s molecules?
slower, and they move around each other.
How can the appearance of a substance CHANGE without it becoming a DIFFERENT substance?
Whether or not a PHASE change occurs is determined by the INTERACTION between the kinetic energy of the molecules and the ATTRACTION pulling the molecules TOGETHER
a pull BETWEEN two molecules that is ALWAYS the SAME for a substance.
Molecular Attraction
The image above shows information about two different substances in sealed containers. At room temperature, both substances are liquids. A scientist transfers the same amount of energy into both substances. One substance changes phase, but the other does not. Which chemical changed phase, and why did it change?
Substance A changed phase because its molecules were able to move fast enough to overcome the attraction between them. Its molecules now move away from each other.
A substance started at 30 degrees Celsius, was placed in the fridge, and two hours later had decreased to 2 degrees Celsius. How do the movement of the molecules change when the temperature decreased?
the movement would've slowed down and moved closer together