Question

when a single salt crystal is added to a cool liquid, large crystals form. which statement about the original cool liquid is correct? (1 point) the liquid is a pure substance because it was uniform before the crystal was added. the liquid is a heterogeneous mixture because the crystals can be easily separated from the liquid. the liquid is a pure substance because it was made up of a single compound. the liquid is a homogeneous mixture because the substance that formed the large crystals was uniformly dissolved.

Explanation:

To solve this, we analyze each option:

• Option 1: A pure substance has a fixed composition. The original liquid was a cool liquid (likely a solvent), and adding a salt crystal (solute) forms a mixture, so it's not a pure substance. Eliminate this.
• Option 2: A heterogeneous mixture has non - uniform composition and visible components. But when a salt crystal dissolves (even if large crystals form later), the original liquid (before adding crystal) was uniform, and the process here leads to a homogeneous mixture (solution) if dissolved, or if crystals form, the mixture with crystals might be heterogeneous, but this option's reasoning is wrong as the original liquid was uniform, not the reason for being heterogeneous. Eliminate this.
• Option 3: A pure substance is made of one type of particle (element or compound). The original cool liquid was likely a single compound (e.g., water) before adding the salt crystal. So it was a pure substance as it was made up of a single compound. This is correct.
• Option 4: A homogeneous mixture has uniform composition. But the original liquid was a pure substance (not a mixture) before adding the salt crystal. The formation of large crystals later doesn't make the original liquid a homogeneous mixture. Eliminate this.

Answer:

The liquid is a pure substance because it was made up of a single compound.