General Science · Practice test 5

Correct answer: asteroid belt

The asteroid belt is a region between Mars and Jupiter containing countless rocky bodies left over from the solar system's formation. The Kuiper belt, farther out past Neptune, is a separate icy region.

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Correct answer: Haemoglobin

Haemoglobin is the iron-bearing protein that grips oxygen in the lungs and releases it in the tissues, and its iron is what makes blood red. Platelets handle clotting and plasma is the liquid the cells float in.

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Correct answer: changes the direction of the effort without reducing it

A fixed pulley has a mechanical advantage of one: you pull down instead of lifting up, which is easier to manage, but the force required is unchanged. Halving the effort takes a movable pulley.

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Correct answer: rock breaking down and mixing with decayed matter

Weathering grinds rock into small particles, and decaying plants and animals add the organic material that makes soil fertile. The process takes centuries, which is why soil loss is hard to reverse.

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Correct answer: smaller acceleration

Newton's second law, force equals mass times acceleration, means for a fixed force, acceleration and mass are inversely related: the heavier object accelerates less.

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Correct answer: air pressure

A barometer reads atmospheric pressure, and falling pressure usually signals approaching bad weather. Humidity is read by a hygrometer and wind speed by an anemometer.

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Correct answer: mineral

A mineral is defined by a consistent chemical formula and crystal arrangement, such as quartz or mica. A rock, by contrast, is usually a mixture of several different minerals.

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Correct answer: memory cells left behind by the immune response

Some lymphocytes produced during an infection persist afterward as memory cells, ready to respond much faster if the same pathogen returns, which is the basis of long-term immunity.

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Correct answer: an undissolved solid from a liquid

Filtration passes a mixture through a barrier fine enough to trap undissolved solid particles while letting the liquid through, which is why it cannot separate something that is fully dissolved.

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Correct answer: a vacuum

Sound is a vibration passed from particle to particle, so it needs a medium. A vacuum has no particles, which is why space is silent. Sound actually travels fastest through solids like steel.

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Correct answer: trapping heat that would otherwise radiate back into space

Greenhouse gases let sunlight through but absorb and re-radiate the heat Earth's surface gives off, trapping extra warmth in the lower atmosphere, which drives global warming.

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Correct answer: a covalent bond

In a covalent bond, atoms share electrons rather than transferring them outright, which is common between two nonmetals such as in water or carbon dioxide.

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Correct answer: Adenine with thymine, cytosine with guanine

The pairing is fixed: A always bonds with T and C always bonds with G. Because the rule is strict, one strand can be used as a template to rebuild the other, which is how DNA copies itself.

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Correct answer: alkali metals

The alkali metals sit in the first column and are highly reactive because they have just one electron in their outer shell, which they readily give up.

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Correct answer: supernova explosion

A very massive star collapses suddenly once fusion can no longer support it, triggering a supernova, an explosive death that can briefly outshine an entire galaxy. Smaller stars like the Sun instead fade gradually into white dwarfs.

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Correct answer: ear

The hammer, anvil, and stirrup sit in the middle ear and pass vibrations from the eardrum inward. The stirrup is the smallest bone in the body.

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Correct answer: One quarter

A Punnett square for Aa x Aa gives genotype ratios of 1 AA : 2 Aa : 1 aa. Only the aa combination shows the recessive trait, which is one out of four offspring.

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Correct answer: acidic

The pH scale runs from 0 to 14 with 7 as neutral. Anything below 7 is acidic and anything above is basic, so 3 is firmly on the acid side.

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Correct answer: produce a temporary magnetic field, an electromagnet

Current flowing through a coiled wire generates a magnetic field, and wrapping it around an iron core concentrates that field, creating an electromagnet that can be switched on and off with the current.

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Correct answer: Nitrogen

Nitrogen accounts for about 78 percent of the air and oxygen for about 21. Carbon dioxide, despite its importance to climate, is well under one percent.

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Correct answer: prompting the body to make antibodies in advance

A vaccine presents a harmless form or fragment of the pathogen so the immune system builds antibodies and memory cells before a real infection arrives. It is preventive, unlike an antibiotic, which attacks bacteria already present.

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Correct answer: does the dissolving

The solvent is the dissolving medium, usually the larger amount, and the solute is what dissolves into it. In salt water, water is the solvent and salt the solute.

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Correct answer: independent variable

The independent variable is the one under the experimenter's control, and the dependent variable is what is measured in response to it. Everything else is held constant so the comparison stays fair.

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Correct answer: 32 degrees

Water freezes at 32 degrees Fahrenheit and boils at 212 degrees, the same two points that read 0 and 100 on the Celsius scale.

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Correct answer: contracts and flattens, drawing air in

The diaphragm contracts downward, enlarging the chest cavity and lowering the pressure inside so air flows in. Breathing out is the reverse: it relaxes and rises.

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