Unit Question
How can the appearance of a substance change without it becoming a different substance?
Chapter 1
Question: What happened to the liquid in Titan’s lake?
Investigations Questions:
How does the appearance of a substance change when it changes phase? (1.2)
What happens to the molecules of a substance when it changes phase? (1.3, 1.4, 1.5, 1.6)
Key Concepts:
(1) A solid holds its shape and does not take the shape of its container. (1.2)
(2) A gas has no visible shape and fills its container. (1.2)
(3) A liquid flows and can take the shape of its container. (1.2)
(1) A solid holds its shape because its molecules only move in place. (1.5)
(2) A gas has no visible shape because its molecules can move away from each other. (1.5)
(3) A liquid can flow because its molecules move around each other. (1.5)
(4) A phase change is when the molecules that make up a substance experience a change to their freedom of movement. This phase change involves a macroscale change in appearance. (1.6)
(5) A change that can be observed at the macroscale can be explained by a change at the molecular scale, which cannot be observed with the naked eye. (1.6)
Chapter 2
Question: What could cause liquid methane to change phase?
Investigations Questions:
What can cause molecules’ freedom of movement to change? (2.1)
Why can transferring energy into or out of a substance change molecules’ freedom of movement? (2.2)
Key Concepts:
(6) When energy is transferred to or from a substance it can change the molecule's freedom of movement
(7) Temperature is a measure of the average kinetic energy of the molecules of a substance
(8) Transferring energy to a substance increases the kinetic energy of that substance's molecules. Transferring energy from a substance decreases the kinetic energy of that substance's molecules.
Chapter 3
Question: Why didn’t the liquid methane change phase before 2007?
Investigations Questions:
Why does an energy transfer not always result in phase change? (3.1, 3.2)
How does molecular attraction affect whether or not a phase change will occur? (3.2, 3.3)
Key Concepts:
(9) 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. (3.2)
(10) The molecular attraction of a substance never changes. (3.2)
(11) A phase change occurs when the kinetic energy increases enough to overcome the attraction between molecules. (3.3)
(12) A phase change occurs when the kinetic energy decreases enough so that the attraction between molecules pulls them together. (3.3)
(13) Different substances can have either weaker or stronger molecular attraction. (3.3)
Chapter 4: Science Seminar
Question: Why is the liquid oxygen machine producing less liquid oxygen than normal?