AST Earth and Physical Science 2 — Questions and Answers
Question 1: Which gas makes up the largest percentage of Earth's atmosphere?
- Oxygen
- Carbon dioxide
- Nitrogen (Correct answer)
- Argon
Correct answer: Nitrogen
Nitrogen makes up approximately 78% of Earth's atmosphere.
Earth's atmospheric composition: ~78% nitrogen (Nâ‚‚), ~21% oxygen (Oâ‚‚), ~0.93% argon (Ar), ~0.04% carbon dioxide (COâ‚‚), plus trace gases. Nitrogen is abundant and relatively inert. Oxygen is critical for respiration. Carbon dioxide is a greenhouse gas important for the carbon cycle.
Question 2: The principle that physical and chemical processes operating today also operated in the past is called:
- Catastrophism
- Uniformitarianism (Correct answer)
- Relativity
- Gradualism
Correct answer: Uniformitarianism
Uniformitarianism is the principle that geological processes have been consistent throughout Earth's history.
Uniformitarianism, developed by James Hutton and popularized by Charles Lyell, holds that the same geological processes (erosion, deposition, volcanism) that operate today operated in the past at similar rates. This contrasts with catastrophism, which attributed geological features to sudden catastrophic events.
Question 3: When an object is in free fall (ignoring air resistance), what force acts on it?
- Normal force only
- Friction only
- Gravity only (Correct answer)
- Gravity and buoyancy
Correct answer: Gravity only
In free fall with no air resistance, only the force of gravity acts on an object.
Free fall is the motion of an object under only the force of gravity, with air resistance ignored. On Earth, all objects in free fall accelerate at approximately 9.8 m/s² regardless of mass (Galileo's experiment). The normal force exists only when an object is on a surface; friction requires contact; buoyancy requires fluid.
Question 4: The transfer of heat through direct contact between materials is called:
- Convection
- Radiation
- Conduction (Correct answer)
- Insulation
Correct answer: Conduction
Conduction is heat transfer through direct physical contact between substances.
Three types of heat transfer: Conduction (through direct contact — molecules transfer energy to adjacent molecules), Convection (through fluid movement — hot fluid rises, cool fluid sinks), Radiation (through electromagnetic waves — no medium required, e.g., solar energy). A metal handle getting hot is conduction; boiling water circulating is convection.
Question 5: A mineral's resistance to being scratched is measured by its:
- Luster
- Hardness (Correct answer)
- Cleavage
- Density
Correct answer: Hardness
Hardness measures a mineral's resistance to scratching, rated on the Mohs scale.
The Mohs Hardness Scale rates minerals from 1 (talc, softest) to 10 (diamond, hardest). Hardness reflects atomic bonding strength. A harder mineral will scratch a softer one. Other mineral properties: luster (how light reflects), cleavage (how it breaks), color, and streak.
Question 6: In the water cycle, the process by which plants release water vapor into the atmosphere is called:
- Evaporation
- Condensation
- Transpiration (Correct answer)
- Infiltration
Correct answer: Transpiration
Transpiration is the release of water vapor from plant leaves into the atmosphere.
Transpiration is the biological component of the water cycle — plants absorb water through roots, use it in photosynthesis, and release excess as water vapor through stomata in leaves. Evapotranspiration combines evaporation from surfaces and transpiration from plants. Forests transpire enormous amounts, influencing local climate.
AST Earth and Physical Science 2
Which gas makes up the largest percentage of Earth's atmosphere?