AZSCI Systems, Energy, and Matter 1 — Questions and Answers
Question 1: A scientist is studying the impact of pesticide runoff on a local river. To accurately analyze the effects, which of the following best defines the system under investigation?
- Only the water in the river.
- The river, its surrounding watershed, the pesticides, and the aquatic organisms. (Correct answer)
- The entire state's water supply.
- Just the chemical composition of the pesticides.
Correct answer: The river, its surrounding watershed, the pesticides, and the aquatic organisms.
A scientific system includes all components relevant to the study, and its boundaries define what is included and excluded. For pesticide runoff, the river itself, its surrounding watershed (where the runoff originates), the pesticides as a chemical input, and the aquatic organisms that are affected are all critical interacting components.
Question 2: In a forest ecosystem, energy flows from sunlight to producers, then to primary consumers, and so on. At each transfer, a significant portion of energy is lost as heat. This phenomenon is best explained by which scientific principle?
- Law of Conservation of Mass.
- First Law of Thermodynamics.
- Second Law of Thermodynamics. (Correct answer)
- Principle of uniformitarianism.
Correct answer: Second Law of Thermodynamics.
The Second Law of Thermodynamics states that in any energy transfer or transformation, some energy is always converted into a less usable form, typically heat, increasing the entropy (disorder) of the system. This explains why energy transfer through trophic levels is inefficient.
Question 3: Which process primarily removes carbon dioxide from the atmosphere and converts it into organic compounds within a terrestrial ecosystem?
- Respiration.
- Decomposition.
- Combustion.
- Photosynthesis. (Correct answer)
Correct answer: Photosynthesis.
Photosynthesis is the fundamental process by which green plants, algae, and some bacteria use sunlight, water, and carbon dioxide to create their own food (glucose) and release oxygen. This process directly removes CO2 from the atmosphere and incorporates it into organic matter.
Question 4: When 10 grams of magnesium reacts completely with 8 grams of oxygen to form magnesium oxide, what is the total mass of the magnesium oxide produced?
- Less than 18 grams.
- Exactly 18 grams. (Correct answer)
- More than 18 grams.
- It depends on the reaction conditions.
Correct answer: Exactly 18 grams.
The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction. Therefore, the total mass of the reactants (magnesium and oxygen) must equal the total mass of the product (magnesium oxide). 10g (magnesium) + 8g (oxygen) = 18g (magnesium oxide).
Question 5: Earth is often described as a system that is largely closed with respect to matter but open with respect to energy. What does this statement imply?
- Both matter and energy freely enter and leave Earth's atmosphere.
- Earth receives significant energy from the sun but exchanges very little matter with space. (Correct answer)
- Earth's total energy content remains constant, but its matter changes significantly.
- Matter is continuously created and destroyed on Earth, while energy is recycled.
Correct answer: Earth receives significant energy from the sun but exchanges very little matter with space.
Earth receives a continuous input of energy from the sun and radiates heat back into space, making it an open system for energy. However, the amount of matter (like rocks, water, and atmospheric gases) entering or leaving Earth's atmosphere is negligible compared to the total mass of the planet, making it largely a closed system for matter.
Question 6: In a predator-prey system, an increase in the prey population often leads to an increase in the predator population, which then causes a decrease in the prey population. This dynamic is an example of a:
- Positive feedback loop.
- Negative feedback loop. (Correct answer)
- Linear progression.
- Isolated system.
Correct answer: Negative feedback loop.
This describes a negative feedback loop. An initial change (increase in prey) triggers a response (increase in predators) that counteracts the initial change (decrease in prey), helping to regulate the system and maintain a dynamic equilibrium or oscillation around a set point.
Question 7: A solar panel converts sunlight into electricity. This process is an example of:
- Matter conservation.
- Energy creation.
- Energy transformation. (Correct answer)
- Energy destruction.
Correct answer: Energy transformation.
Energy transformation (or conversion) is the process of changing energy from one form to another. Solar panels convert radiant energy (from sunlight) into electrical energy. The Law of Conservation of Energy states that energy cannot be created or destroyed, only transformed.
AZSCI Systems, Energy, and Matter 1
A scientist is studying the impact of pesticide runoff on a local river.
To accurately analyze the effects, which of the following best defines the system under investigation?