General Science · Practice test 2

Correct answer: an electrical impulse

Signals travel down a neuron electrically, then cross the gap to the next neuron chemically. Hormones are the endocrine system's slower method of sending messages through the blood.

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Correct answer: The neutron

The neutron is neutral, as its name suggests. Protons are positive, electrons are negative, and an ion is an atom that has gained or lost electrons rather than a particle in its own right.

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Correct answer: mass

The more mass an object has, the harder it is to start it moving or to stop it. That is why a loaded truck needs far more distance to halt than an empty one at the same speed.

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Correct answer: Skeletal muscle

Skeletal muscle attaches to bone and is under conscious control. Smooth muscle works the internal organs and cardiac muscle the heart, both without any decision on your part.

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Correct answer: Transcription of DNA into mRNA, then translation of mRNA into protein

A gene is first transcribed into messenger RNA inside the nucleus, and that mRNA is then translated at a ribosome into a chain of amino acids that folds into a protein.

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Correct answer: stratosphere

The stratosphere is the second layer up, above the troposphere where weather happens, and the ozone within it screens out most ultraviolet radiation.

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Correct answer: a homogeneous mixture

Salt water is a homogeneous mixture, or solution: the dissolved salt is spread evenly throughout so any sample looks and tastes the same. A heterogeneous mixture, like sand in water, is visibly uneven.

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Correct answer: water's polar molecules pull apart the ionic lattice

Water molecules are polar, with a slightly negative oxygen end and slightly positive hydrogen ends, which let them surround and pull apart the positive and negative ions locked in salt's crystal lattice.

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Correct answer: The Milky Way

The Milky Way is our home galaxy, a spiral of a few hundred billion stars. Andromeda is the nearest large neighbour, and the Orion Nebula is a cloud of gas inside our own galaxy.

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Correct answer: Red

Across the visible spectrum wavelength decreases from red through orange, yellow, green, and blue to violet. Beyond red lies infrared and beyond violet lies ultraviolet.

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Correct answer: halogens

The halogens are highly reactive nonmetals that need just one more electron to fill their outer shell, which is why they readily form compounds with metals such as sodium.

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Correct answer: a fibrous joint

Fibrous joints like the sutures of the skull are locked tightly together for protection rather than movement. Ball-and-socket and hinge joints, by contrast, allow a wide range of motion.

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Correct answer: groundwater

Groundwater accumulates in soil and rock below the surface, feeding wells and springs. Runoff, by contrast, is water that flows over the surface instead of soaking in.

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Correct answer: a salt and water

In a neutralization reaction, the hydrogen ions from an acid combine with the hydroxide ions from a base, forming water, while the leftover ions form a salt.

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Correct answer: continue sliding at the same speed and direction forever

Inertia is an object's tendency to resist a change in its motion. With no friction or other outside push acting on it, the puck has nothing to change its speed or direction, so it glides on unchanged.

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Correct answer: wind speed

An anemometer, typically a set of spinning cups, measures how fast the wind is blowing. Air pressure is read with a barometer and humidity with a hygrometer.

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Correct answer: Scurvy

Scurvy comes from a lack of vitamin C and was once common among sailors without fresh fruit. Rickets follows a vitamin D shortage, anaemia usually an iron shortage, and goitre an iodine shortage.

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Correct answer: nucleus

Protons and neutrons, both far heavier than electrons, sit together in the tiny, dense nucleus at an atom's center, accounting for nearly all of its mass.

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Correct answer: The kilogram

Mass is measured in kilograms. The newton measures the force of weight, which changes with gravity even though mass does not, so the two are not interchangeable.

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Correct answer: an estuary

An estuary is the partially enclosed coastal body of water where river and ocean water mix, creating a distinct, nutrient-rich habitat for many species.

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Correct answer: 30 watts

Power equals work divided by time, so 600 joules divided by 20 seconds gives 30 watts.

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Correct answer: photosynthesis in plants and algae

Photosynthesis pulls carbon dioxide out of the air and locks the carbon into sugars. Respiration, decomposition, and burning fossil fuels all release carbon dioxide back into the atmosphere instead.

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Correct answer: ovule

The ovule, inside the ovary, contains the egg cell and develops into a seed once it is fertilized by pollen. The stamen and stigma are involved earlier, in producing and receiving pollen.

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Correct answer: newtons

Force is measured in newtons, energy and work in joules, and power in watts. The kilogram measures mass, which is not the same thing as the force of weight acting on it.

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Correct answer: nuclear fusion converting hydrogen into helium

Deep in the Sun's core, immense pressure and temperature fuse hydrogen nuclei into helium, releasing the enormous energy that powers sunlight and heat.

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