Electrolytes are substances that form mobile ions in a medium, so they can carry an electric current. You can identify them by their conductivity: if a compound conducts electricity when dissolved in water or when melted, it is producing ions in that medium. Ionic compounds dissociate into ions in aqueous solution, and strong acids and bases also dissociate completely into ions, making the solution a good conductor. When an ionic compound is melted, the solid’s ions are free to move, so melting also allows conduction. In contrast, most covalent compounds that do not ionize—like sugar in water—don’t produce free ions and thus do not conduct electricity, so they’re non-electrolytes. There are also weak electrolytes that only partially ionize and conduct only weakly, but the guiding behavior is the presence of free ions in solution or melt.

Covalent compounds are made of molecules held together by covalent bonds, so they don’t form free ions easily. This leads to two typical trends: weaker forces between molecules compared to ionic lattices, and lack of charged particles to carry current. As a result, they usually melt and boil at lower temperatures than ionic substances, and they don’t conduct electricity in either the solid or melted state (they’re often non-electrolytes when dissolved). There are exceptions—some covalent substances can ionize in water (like certain acids) or exist as network solids with high melting points—but the general pattern for covalent compounds is lower melting points and nonconductivity. The other statements describe ionic behavior (high melting points with SAMPLEmolten conductivity or complete ionization in water), which doesn’t fit covalent compounds as a broad rule.

The main idea being tested is how electron arrangement distinguishes ionic and covalent bonds. Ionic bonds form when one atom donates electrons to another, creating ions that attract each other through electrostatic forces. This transfer and resulting charged particles are what hold ionic compounds together, and it’s why they often form crystalline solids with high melting points. This description directly contrasts with covalent bonds, where atoms share electron pairs rather than transfer electrons to form ions. In covalent bonds, electrons are shared to achieve stability, so the atoms stay as neutral entities rather than becoming ions. The bond strength comes from the shared electrons rather than an electrostatic attraction between ions. Because of this fundamental difference, covalent compounds can exist as discrete molecules or network structures with a range of melting points, not inherently defined by lattice formation and strong ionic attractions. The other statements mischaracterize the contrasts. Covalent bonds do not involve transferring electrons to form charged ions. Saying covalent bonds involve sharing electron pairs is correct for covalent bonds, but it doesn’t describe the contrasting idea with ionic bonds. And while some covalent networks have high melting points, lattice structures with high melting points are not the defining contrast between ionic and covalent bonding.

Protecting eyes, skin, and breathing is the central idea behind PPE in a chemistry lab. The most appropriate set includes safety glasses or goggles to shield the eyes, a lab coat to protect skin and clothing from spills, and chemical-resistant gloves to prevent direct contact with hazardous substances. Some tasks or hazards require extra protection, so a face shield can be added for splashes, a respirator for inhalation hazards, and sturdy closed-toe shoes for foot protection. This combination covers the main exposure routes and adapts to different experiments. Choosing with too little protection—like skipping gloves or PPE entirely—risks exposure, which is why the more comprehensive option is the best choice.