Science: Chemistry and Physical Science Flashcards

What is the pH of a neutral solution at 25°C?

Answer: 7

A neutral solution has a pH of 7, where the concentration of hydrogen ions (H⁺) equals the concentration of hydroxide ions (OH⁻).

Which of the following best describes an acid according to the Brønsted-Lowry definition?

Answer: A substance that donates protons (H⁺)

In the Brønsted-Lowry theory, an acid is a proton (H⁺) donor — it releases H⁺ ions in solution.

In a chemical equation, what does the law of conservation of mass require?

Answer: The number of atoms of each element must be equal on both sides of the equation

The law of conservation of mass states that matter cannot be created or destroyed — the total mass and number of atoms of each element must be the same on both sides of a chemical equation.

Which of the following best describes a physical change?

Answer: Water boiling and turning to steam

Water boiling is a physical change — the chemical composition (H₂O) does not change, only the physical state (liquid to gas).

What is the atomic number of an element?

Answer: The number of protons in the nucleus of an atom

The atomic number (Z) is the number of protons in the nucleus, which uniquely identifies the element and determines its position on the periodic table.

Which type of chemical bond involves the sharing of electrons between atoms?

Answer: Covalent bond

Covalent bonds form when atoms share pairs of electrons, commonly between nonmetal atoms.

When a patient receives an IV solution of normal saline (0.9% NaCl), which type of solution is this relative to normal blood plasma?

Answer: Isotonic solution

Normal saline (0.9% NaCl) is isotonic to blood plasma — it has the same solute concentration as blood, preventing osmotic shifts in red blood cells.

Which of the following statements about enzymes is TRUE?

Answer: Enzymes lower the activation energy required for a chemical reaction.

Enzymes are biological catalysts that lower the activation energy needed for a reaction, allowing it to proceed faster without being consumed in the process.

What is the difference between an element and a compound?

Answer: An element contains only one type of atom; a compound contains two or more elements chemically bonded together

An element is a pure substance consisting of only one type of atom (e.g., oxygen O₂). A compound is a pure substance formed when two or more different elements are chemically bonded in fixed proportions (e.g., water H₂O).

Which of the following correctly describes the relationship between the frequency and wavelength of electromagnetic radiation?

Answer: Frequency and wavelength are inversely proportional; as wavelength increases, frequency decreases

Frequency (ν) and wavelength (λ) are inversely proportional: ν = c/λ, where c is the speed of light. As wavelength increases, frequency decreases, and vice versa.

In chemistry, what is a solution?

Answer: A homogeneous mixture in which a solute is uniformly dissolved in a solvent

A solution is a homogeneous mixture where a solute (dissolved substance) is uniformly distributed throughout a solvent (dissolving medium), such as salt dissolved in water.

What happens during an exothermic chemical reaction?

Answer: Energy is released to the surroundings, causing the system to warm

In an exothermic reaction, the products have less energy than the reactants, so the energy difference is released to the surroundings as heat, light, or other forms.

Which of the following is an example of a chemical property?

Answer: Hydrogen gas is highly flammable

Flammability describes how a substance reacts with oxygen (a chemical change) — this is a chemical property. The others describe physical properties observed without changing the substance.

In the context of nuclear science, what is radioactive decay?

Answer: A process where an unstable nucleus spontaneously emits particles or energy to become more stable

Radioactive decay is the spontaneous emission of particles or energy from an unstable atomic nucleus as it transforms into a more stable configuration.

What is the difference between a cation and an anion?

Answer: Cations are positively charged (lost electrons); anions are negatively charged (gained electrons)

Cations form when an atom loses electrons (becoming positively charged); anions form when an atom gains electrons (becoming negatively charged).

Which of the following correctly describes the behavior of molecules during diffusion?

Answer: Molecules move from areas of high concentration to low concentration

During diffusion, molecules move randomly but the net movement is from areas of high concentration to low concentration, down the concentration gradient, until equilibrium is reached.

Which of Newton's laws states that an object in motion stays in motion unless acted upon by an external force?

Answer: Newton's First Law (Law of Inertia)

Newton's First Law (Law of Inertia) states that an object will remain in its current state of motion (rest or constant velocity) unless acted upon by a net external force.

The atomic mass of carbon is approximately 12 amu. What does this value represent?

Answer: The weighted average mass of naturally occurring carbon isotopes

Atomic mass is the weighted average of the masses of all naturally occurring isotopes of an element, taking into account their relative abundances.

Which state of matter has definite volume but no definite shape?

Answer: Liquid

A liquid has a definite volume but takes the shape of its container — it has no definite shape. Solids have both definite shape and volume; gases have neither.

Which of the following best describes the scientific method?

Answer: A systematic process of observation, hypothesis formation, experimentation, and conclusion to investigate natural phenomena

The scientific method is a systematic approach to investigation involving observation, hypothesis, testing, data collection, analysis, and conclusion — it is iterative and self-correcting.