TExES Core Subjects EC-6 Science (904) practice test

A chemical that cannot be identified must be treated as potentially hazardous. The safe course is to leave the bottle closed, mark it as an unknown and set it aside for removal through the school district's hazardous-waste procedures. Pouring, smelling or testing the liquid would expose people or the environment to a substance whose hazards no one knows.

A

Only substances known to be safe for the sewer may go down a drain, and an unlabeled liquid could be toxic, flammable or reactive.

B

Wafting is the proper way to smell a known substance, but odor cannot reliably identify an unknown liquid, and its vapor could be harmful.

D

pH paper shows only whether a liquid is acidic, basic or neutral, which cannot identify it, and opening the bottle adds exposure to an unknown hazard.

Inquiry is most meaningful when it grows out of questions and issues that matter to students, such as something they have noticed at home or on the playground. Basing an investigation on a question the students themselves raised connects the work to their experience and gives them a reason to want the answer. A textbook question, a famous historical experiment and a generic list of fair topics can all lead to sound investigations, but none starts from the students' own questions.

B

A question from the textbook's review comes from the curriculum rather than from students' experience, so it ignores the stated goal of relevance.

C

Replicating a famous experiment teaches the history and methods of science, a different goal, and the question belongs to the original scientist rather than to the students.

D

A list of fair ideas offers a choice among topics, but the topics come from someone else rather than from the students' own lives, so it meets only part of the goal.

Mendeleev arranged the 63 elements known in his time by atomic mass and saw that similar properties recur at regular intervals. Where the pattern called for an element no one had found, he left a gap and predicted its properties from those of its neighbors; gallium, found in 1875, and germanium, found in 1886, closely matched his descriptions. A pattern in observations, not knowledge of atomic structure, made the predictions possible.

B

The modern table is ordered by the number of protons, but atomic number was not established until 1913, more than 40 years after these predictions, so this is an anachronism.

C

No element was made artificially until 1937, and gallium and germanium occur in nature, so no such experiment produced them for Mendeleev.

D

Electron arrangements do explain why properties repeat, but electrons were not discovered until 1897, so this true explanation was not available to Mendeleev and did not make his predictions possible.

An assessment is aligned with an objective when it asks students to do what the objective states, here explaining how a beak's shape relates to the food a bird gets. Matching beak shapes to foods and justifying each match requires exactly that reasoning about form and function. The other tasks check beak parts, bird diets or foot shapes, so each measures only part of the objective or a different one.

A

Labeling beak parts checks anatomy vocabulary but never asks students to connect a beak's shape to the food the bird gets.

B

Listing what birds eat addresses food alone and leaves out the beak, so it measures only half of the relationship the objective names.

C

Sorting birds by foot shape assesses a different structure, not the beak-and-food relationship the objective targets.

Density is mass divided by volume, and the volume of a rectangular block is the product of its three dimensions: 2 cm × 3 cm × 5 cm = 30 cm³. The density is therefore 81 g ÷ 30 cm³ = 2.7 g/cm³, the density of aluminum.

A

Divides the volume by the mass (30 ÷ 81), which inverts the ratio that defines density.

C

Divides the mass by the sum of the dimensions (2 + 3 + 5 = 10) instead of their product, so the number used is not the block's volume.

D

Divides the mass by the 6 cm² area of one 2 cm × 3 cm face, confusing area with volume by leaving out the block's third dimension.

The bubbles are mostly oxygen released by photosynthesis, which runs on light energy absorbed by the plant's chlorophyll. Moving the lamp away lowers the light reaching the leaves, so less light energy is changed into chemical energy, photosynthesis slows and fewer bubbles form. Keeping the water temperature the same rules out heat as the cause.

A

Moving the lamp does not change how much carbon dioxide is dissolved in the water, so it cannot explain the drop in bubbles.

C

The stem states that the water temperature stayed the same, which rules out a change in heat from the lamp as the cause.

D

Plants carry out respiration in light and darkness alike, so dimmer light slows photosynthesis rather than switching the plant to another process.

Xylem is the tissue that carries water and dissolved substances from a plant's roots up to its leaves. Water drawn into the cut stalk moves up through the xylem and carries the dissolved dye with it, so the red dots students see mark the xylem in the stalk's bundles of conducting tissue. Phloem, the other conducting tissue, moves sugars made in the leaves rather than water taken in from below.

A

Phloem is the neighboring conducting tissue, but it carries sugars made in the leaves to other parts of the plant rather than the tinted water drawn up the stalk.

B

Cambium is a layer of dividing cells that produces new xylem and phloem; it builds conducting tissue but does not itself carry water up the stalk.

D

The epidermis is the stalk's thin protective outer layer, while the dye showed up as dots inside the stalk, where the conducting tissue runs.

A dark back over a pale belly is called countershading. Seen from above, the dark back blends with the dim water below, and seen from below, the pale belly blends with the bright, sunlit surface, so the fish is harder for predators and prey to spot. Individuals with this camouflage are more likely to survive and reproduce.

B

Warning coloration uses bright, contrasting patterns that make an animal stand out, while a dark back and pale belly make these fish harder to see.

C

Mating colors are usually bright or appear only in the breeding season, whereas this dark-over-pale pattern lasts all year and lowers visibility.

D

Looking like a more dangerous species is mimicry, which copies another animal's pattern; this coloring instead matches the fish to the light above and below it.

Where an ocean plate converges with a continent, the denser ocean plate sinks beneath the continental plate in a process called subduction, and the seafloor bends down into a deep trench where it descends. As the plate sinks deeper into the mantle, water driven out of it lowers the melting point of the rock above, and the magma that forms rises to build a chain of volcanoes inland, parallel to the trench. Along most of South America's west coast, the Nazca plate is sinking beneath the South American plate, forming the offshore trench and the volcanoes of the Andes.

B

When two continental plates collide, neither sinks far because continental crust is too buoyant, so the crust crumples into high mountains without forming a deep trench or a chain of volcanoes.

C

Plates that move apart open a rift or a mid-ocean ridge where new crust forms, so divergence cannot produce a trench, the place where a plate sinks.

D

A hot spot can build a chain of volcanoes, but it forms no trench, so it explains the volcanoes and leaves the trench unexplained.

The dew point is the temperature at which air becomes saturated, so a gap of only 12 − 11 = 1 °C means this air is already close to saturation. Under a clear sky with calm winds, the ground radiates energy to space after sunset and chills the air just above it, and the calm keeps that cooled layer from mixing with warmer air above. Once the air cools to its dew point, water vapor condenses into tiny droplets that hang near the ground as fog, most often in low areas where cold air collects.

A

A neighboring term: frost forms only on surfaces at 0 °C or below, far under this evening's 12 °C, and in air this moist the temperature usually levels off near the 11 °C dew point, so the water collects as liquid drops, not ice.

C

Rests on the misconception that nearly saturated air means rain: steady rain falls from thick clouds built by air rising over a wide area, and the stated clear, calm sky shows no such lifting.

D

Ignores the stated data: a temperature only 1 °C above the dew point means the air is nearly saturated, and cooling through the night moves it closer to saturation, not toward drier air.