ATI TEAS 7 — All Questions

Two parents are each heterozygous for a trait (Aa). What fraction of their offspring is expected to show the recessive trait?

• a.One quarter✓
• b.One half
• c.None of them
• d.Three quarters

A Punnett square for Aa x Aa gives AA, Aa, Aa, and aa, so only the one aa offspring in four shows the recessive trait. Three quarters show the dominant trait, and one half is the fraction that is heterozygous.

Which equation summarizes aerobic cellular respiration?

• a.Glucose alone yields oxygen and lactic acid
• b.Carbon dioxide plus water yields glucose plus oxygen
• c.Glucose plus oxygen yields carbon dioxide, water, and ATP✓
• d.Water plus sunlight yields glucose and carbon dioxide

Cells oxidize glucose with oxygen to release energy, giving off carbon dioxide and water. The choices that start from carbon dioxide, or from water and sunlight, describe photosynthesis or a garbled version of it, and lactic acid forms only in anaerobic conditions without producing oxygen.

What happens to an enzyme when it is exposed to high heat or extreme pH?

• a.It doubles the number of active sites it has
• b.It denatures and loses its functional shape✓
• c.It becomes permanently faster at its reaction
• d.It is converted into a carbohydrate

Enzymes are proteins whose activity depends on a precise three-dimensional shape, and harsh conditions unfold that shape so the substrate no longer fits. Enzymes do not gain speed, change into other macromolecules, or add active sites under stress.

Which subatomic particle determines the identity of an element?

• a.The neutron
• b.The positron
• c.The proton✓
• d.The electron

The number of protons is the atomic number and defines which element an atom is. Changing neutrons produces an isotope of the same element, changing electrons produces an ion, and positrons are not part of a stable atom.

An atom's mass number is calculated by adding which two values?

• a.Protons and neutrons✓
• b.Electrons and neutrons
• c.Neutrons and valence electrons
• d.Protons and electrons

Mass number counts the particles in the nucleus, which are the protons and neutrons. Electrons have so little mass that they are not included in the total.

What happens to electrons when an ionic bond forms between two atoms?

• a.They are transferred from one atom to the other✓
• b.They are destroyed and converted into energy
• c.They orbit both nuclei in a single shared shell
• d.They are shared equally between the two atoms

In an ionic bond one atom gives up electrons and the other accepts them, producing oppositely charged ions that attract. Equal sharing describes a nonpolar covalent bond, and electrons are never destroyed in chemical bonding.

A solution has a pH of 4. How does it compare to a solution with a pH of 6?

• a.It is slightly more basic
• b.It is twice as acidic
• c.It is 100 times more acidic✓
• d.It is exactly the same acidity

The pH scale is logarithmic, so each whole unit is a tenfold change in hydrogen ion concentration and two units is ten times ten. A lower pH means more acidic, not more basic, and the difference is far larger than double.

In a saltwater solution, which component is the solvent?

• a.The salt
• b.The water✓
• c.The dissolved ions
• d.The container

The solvent is the substance present in greater amount that does the dissolving, which is water here. Salt is the solute, the ions are what the solute becomes, and the container plays no chemical role.

According to the law of conservation of mass, in a closed chemical reaction the total mass of the products is:

• a.Always greater than the mass of the reactants
• b.Equal to the total mass of the reactants✓
• c.Always less than the mass of the reactants
• d.Unrelated to the mass of the reactants

Atoms are rearranged rather than created or destroyed, so mass is conserved in a closed system. Any gain or loss observed in an open container reflects gas escaping or entering rather than a change in total mass.

Which change of state describes a gas becoming a liquid?

• a.Sublimation
• b.Melting
• c.Evaporation
• d.Condensation✓

Condensation is the transition from gas to liquid, as when water droplets form on a cold glass. Evaporation runs the other direction, melting turns a solid to a liquid, and sublimation takes a solid straight to a gas.

What does a catalyst do in a chemical reaction?

• a.It changes the products the reaction will make
• b.It is consumed and must be replaced each time
• c.It raises the energy needed to start the reaction
• d.It speeds the reaction by lowering activation energy✓

A catalyst provides an easier pathway with lower activation energy and emerges unchanged at the end. It does not alter what products form, is not used up, and lowers rather than raises the energy barrier.

A researcher tests whether a fertilizer increases plant height. What is the dependent variable?

• a.The height of the plants✓
• b.The amount of fertilizer applied
• c.The type of soil used in each pot
• d.The number of hours of daylight

The dependent variable is the outcome measured in response to the treatment, which is plant height. The fertilizer amount is the independent variable, and soil type and daylight are constants that should be held the same.

Why do scientists repeat an experiment several times before accepting a result?

• a.Repeating shortens the time the experiment requires
• b.Repeating reduces the influence of chance on the result✓
• c.Repeating makes the measuring instruments more precise
• d.Repeating guarantees the hypothesis will be proved

Replication shows whether an outcome is consistent or was a fluke of a single trial. Repetition cannot prove a hypothesis, does not improve the instruments themselves, and generally takes more time rather than less.

How does a scientific theory differ from a hypothesis?

• a.A theory cannot be tested while a hypothesis can
• b.A theory applies to one experiment at a time
• c.A theory is a guess while a hypothesis is proven
• d.A theory is supported by a large body of evidence✓

A theory is a broad explanation that has survived extensive testing, while a hypothesis is a specific testable prediction. Calling a theory a guess reverses the two, and theories remain testable and explain many observations rather than one.

Which instrument would a student use to measure the volume of a liquid most precisely?

• a.A graduated cylinder✓
• b.A thermometer
• c.A triple-beam balance
• d.A metric ruler

A graduated cylinder is marked in milliliters and is read at the bottom of the meniscus. A balance measures mass, a ruler measures length, and a thermometer measures temperature.

How many milligrams are in one gram?

• a.1,000✓
• b.1,000,000
• c.100
• d.10

The prefix milli means one thousandth, so a gram contains 1,000 milligrams. One hundred would match centigrams, ten is far too few, and a million milligrams would equal a kilogram.