HiSET Science Practice Test #2 3 Flashcards

What is the difference between a hypothesis and a theory in science?

Answer: A hypothesis is a testable prediction; a theory is a well-supported explanation backed by extensive evidence

A hypothesis is a testable, falsifiable prediction made before an experiment. A scientific theory is a well-substantiated explanation supported by repeated testing and a large body of evidence — not a guess.

Which force keeps planets in orbit around the sun?

Answer: Gravity

Gravity is the attractive force between masses. The sun's gravitational pull on the planets provides the centripetal force that keeps them in orbit rather than flying off in a straight line.

Which part of the human nervous system is responsible for voluntary muscle movements?

Answer: Somatic nervous system

The somatic nervous system controls voluntary actions — movements you consciously initiate, such as picking up an object or walking. The autonomic nervous system controls involuntary functions like heartbeat and digestion.

In a chemical reaction, what is a catalyst?

Answer: A substance that speeds up a reaction without being permanently changed

A catalyst increases the rate of a chemical reaction by lowering the activation energy needed. It participates in the reaction but is regenerated at the end, so it is not permanently consumed.

What is the primary driver of plate tectonics?

Answer: Convection currents in the mantle

Convection currents in Earth's semi-fluid mantle are driven by heat from the core. This movement drags the tectonic plates that sit on top of the mantle, causing them to move apart, collide, or slide past each other.

In DNA, which base pairs with adenine (A)?

Answer: Thymine (T)

In DNA, adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). These are called complementary base pairs. (In RNA, uracil replaces thymine.)