AZSCI Systems, Energy, and Matter

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?

Accepted Answer

The river, its surrounding watershed, the pesticides, and the aquatic organisms.

Answer

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?

Accepted Answer

Second Law of Thermodynamics.

Answer

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?

Accepted Answer

Photosynthesis.

Answer

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?

Accepted Answer

Exactly 18 grams.

Answer

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?

Accepted Answer

Earth receives significant energy from the sun but exchanges very little matter with space.

Answer

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.

(AZSCI) Arizona Science Test Practice Test

(AZSCI) Arizona Science Test Practice Test

AZSCI Systems, Energy, and Matter