General Science Practice Test 1

Answer: D

Correct answer: Freezing fruit juice into ice pops. A physical change alters only form or state. After freezing, the juice is still the same substance, just solid. Toasting, burning and rusting all produce new substances.

• A: Browning forms new compounds with new flavors and colors, which makes it a chemical change.
• B: Rust is iron oxide, a new compound, so rusting is a chemical change.
• C: Combustion turns propane and oxygen into carbon dioxide and water, which are new substances.
• D (correct): Frozen juice is still the same juice in solid form, so only its state changed.

Answer: B

Correct answer: Six hundred fifty milliliters. Multiply liters by 1,000:

• A: 6,500 mL equals 6.5 L.
• B (correct): Correct: 650 mL.
• C: 65 mL equals 0.065 L.
• D: 0.065 mL is far smaller than 0.65 L.

Answer: D

Correct answer: A fungus growing on dead leaves. Decomposers, mainly fungi and bacteria, obtain energy by breaking down dead organisms and wastes. Fungi release digestive enzymes into the material and then absorb the dissolved nutrients, which returns elements such as nitrogen and phosphorus to the soil for plants. To recognize a decomposer, look for an organism feeding on dead matter rather than catching or grazing on living things. Animals eating living food are consumers, even if they eat small organisms like plankton.

• A: A fish feeding on plankton is a consumer.
• B: A hawk catches and eats live prey, so it is a predator and consumer.
• C: A rabbit eats living plants, so it is an herbivorous consumer.
• D (correct): Many fungi chemically break down dead matter.

Answer: B

Correct answer: Noble gases. Helium, neon and argon sit in group 18. This family, the noble gases, has full outer electron shells, so its members are the least reactive elements.

• A: Alkali metals are the soft, reactive group 1 metals such as sodium and potassium.
• B (correct): Helium, neon and argon are in group 18, the noble gases, which have full outer shells and rarely react.
• C: Alkaline earth metals are the group 2 metals such as magnesium and calcium.
• D: Halogens are the group 17 nonmetals such as fluorine and chlorine, which are highly reactive.

Answer: C

Correct answer: Esophagus. Swallowed food is pushed down the esophagus by peristalsis, waves of muscle contraction that work even when you are lying down. The esophagus lies behind the trachea, and both start at the throat, so a flap called the epiglottis covers the airway during swallowing to keep food out of the lungs. The trachea is the tempting choice because it also runs from the throat into the chest, but it carries air, not food.

• A: The thoracic aorta is a major artery that carries blood, not swallowed food.
• B: The common bile duct carries bile toward the small intestine, not food from the throat.
• C (correct): Peristaltic contractions transport swallowed material through the esophagus.
• D: The trachea carries inhaled and exhaled air, not swallowed food.

Answer: D

Correct answer: Axon. A neuron receives signals on its dendrites, integrates them at the cell body, and sends an electrical impulse out along a single axon to its terminals, where neurotransmitters pass the message to the next cell. Many axons are wrapped in myelin, which speeds conduction. A useful memory hook is that the axon sends signals away, while dendrites, like branching tree limbs, collect incoming signals. Dendrites are the tempting wrong answer because both are neuron extensions.

• A: Dendrites primarily receive many incoming signals.
• B: An alveolus is a lung air sac.
• C: A ligament connects bones, not neural information.
• D (correct): The axon conveys impulses toward other neurons, muscle or glands.

Answer: A

Correct answer: 5 mg/L. Concentration is the amount of solute divided by the volume it is spread through. Here 15 mg spread evenly through 3 L gives

mg in each liter. The unit itself shows the operation: mg/L means milligrams divided by liters. Multiplying or adding the values gives numbers that do not describe how much solute is in each liter. Water-quality limits for substances such as nitrate are usually reported in exactly these units.

• A (correct): 15 mg / 3 L = 5 $\frac{\mathrm{mg}}{\mathrm{L}}$.
• B: This is the reciprocal of the stated ratio with inappropriate units.
• C: Multiplication gives total scale, not concentration.
• D: Addition of milligrams and liters is not meaningful.

Answer: B

Correct answer: 5. Diploid cells carry two sets of chromosomes, one from each parent, while haploid cells carry one set. Meiosis separates the members of each homologous pair, so the gamete count is always half the diploid number:

Fertilization then joins two gametes of 5 to restore 10. A common slip is keeping the count at 10, as mitosis would, or doubling it; the human version of the same rule is 46 halved to 23.

• A: This doubles rather than halves the diploid count.
• B (correct): The haploid set is half the diploid count of 10.
• C: This preserves the diploid count and ignores reduction.
• D: Haploid does not mean two chromosomes.

Answer: A

Correct answer: Secondary succession. Succession is the gradual change in species after a disturbance. Secondary succession happens where soil, seeds or roots survive, as after a fire, flood or abandoned farm, so recovery can start quickly with grasses and shrubs. Primary succession begins on surfaces with almost no soil, like new lava or rock exposed by a retreating glacier, and must wait for pioneer species to build soil. The key clue is whether the soil remains.

• A (correct): Soil and biological remnants generally permit secondary succession.
• B: Nitrogen fixation is a nutrient transformation.
• C: Biomagnification is contaminant increase through a food chain.
• D: Primary succession starts on substrates with virtually no developed soil.

Answer: B

Correct answer: Fluorine. Seven valence electrons place an element in group 17, the halogens. The halogen in the second row (period 2) is fluorine; chlorine is the one below it in period 3.

• A: Neon is in period 2 but is a noble gas with a full set of 8 valence electrons.
• B (correct): Fluorine is in period 2 and group 17, so it has 7 valence electrons.
• C: Chlorine also has 7 valence electrons, but it is in period 3, not period 2.
• D: Nitrogen is in period 2 but is in group 15 with 5 valence electrons.

Answer: D

Correct answer: 24 J. Kinetic energy depends on mass and the square of speed: KE = ½mv². Square the speed first, 4² = 16, then multiply by the mass,

and finally take half, which gives 24 joules. Because speed is squared, doubling the speed would quadruple the energy. The usual mistakes are forgetting the factor of ½ or multiplying by the speed without squaring it.

• A: Forty-eight joules forgets to divide mass times speed squared by two.
• B: Six joules results from treating speed as a simple factor without the square and correct coefficient.
• C: Twelve joules multiplies the mass by the unsquared speed, missing the speed-squared factor.
• D (correct): KE = $\frac{1}{2}$ × 3 × $4^2$ = 24 J using the correct units.

Answer: B

Correct answer: Main sequence → red giant → white dwarf. When a Sun-like star uses up the hydrogen in its core, the core contracts while the outer layers expand and cool, making a red giant. Later the star sheds its outer layers, and the exposed hot core remains as a dense, Earth-sized white dwarf that slowly cools. Supernovae, neutron stars and black holes require stars roughly eight or more times the Sun's mass, so they do not fit a star like the Sun.

• A: The Sun is not massive enough for the usual core-collapse pathway.
• B (correct): Sun-like stars swell as red giants and leave white-dwarf remnants.
• C: A white dwarf does not normally become a gas giant and then a star.
• D: A neutron star normally comes from massive-star core collapse.

Answer: D

Correct answer: 144 m. Treat each stage separately.

Stage 1:

Stage 2:

Total:

• A: This uses the final 12 m/s for the whole 14 s, ignoring the slower speeds during the first stage.
• B: This counts only the cruising stage and leaves out the 24 m covered while speeding up.
• C: This applies the acceleration for all 14 s, though the tram stopped accelerating after 4 s.
• D (correct): Stage 1 covers 24 m and ends at 12 m/s; stage 2 covers 12 × 10 = 120 m; the total is 144 m.

Answer: D

Correct answer: A single cold day is weather and does not by itself overturn the long-term climate trend. Weather is the day-to-day state of the atmosphere, while climate is the average pattern over decades, usually about 30 years. Trends are judged statistically across many data points, and individual cold or hot days are expected noise around the trend. A useful hook: climate is what you expect, weather is what you get.

• A: One day is insufficient to assess a statistical multi-decade trend.
• B: Weather is a short-term condition, while climate describes long-term patterns that one day cannot reverse.
• C: Temperature remains a key climate variable, alongside precipitation and other measures.
• D (correct): One observation of short-term weather does not invalidate a trend evaluated over many years.

Answer: D

Correct answer: They could be nonphotosynthetic eukaryotic cells, such as certain fungal or plant cells. Mitochondria and a nucleus show the cells are eukaryotic, which immediately rules out bacteria. A cell wall narrows the list to plants, fungi, or some protists, since animal cells lack walls. Missing chloroplasts does not rule out plants, because root cells lack them, and fungi never have chloroplasts but get energy by absorbing food. Defensible conclusions use words like could, while choices that use must or definitely overreach the evidence.

• A: Typical animal cells have no walls.
• B: Bacteria lack mitochondria and membrane-bound nuclei, so these features point away from bacteria.
• C: Many living cells, such as fungal and animal cells, get energy from food molecules instead of from photosynthesis.
• D (correct): Correct: Nucleus and mitochondria support eukaryotic classification; walls can occur in fungi and plants without chloroplasts.