What is Dry Ice?

Dry ice is the solid form of carbon dioxide (CO₂). It is called "dry" ice because it does not melt into a liquid when it warms up; instead, it undergoes a process called sublimation, where it changes directly from a solid to a gas.

Step-by-Step Explanation:

Step 1: Identify the chemical compound. Carbon dioxide is a gas at room temperature and is represented by the chemical formula ${CO}_{2}$ .

Step 2: Understand the state change. When carbon dioxide is cooled to a very low temperature (approximately $- 78.5 ° C$ or $- 109.3 ° F$ ), it solidifies without passing through a liquid phase under normal atmospheric pressure.

Step 3: Compare with the options. The correct description from the given choices is "solid carbon-dioxide".

Final Answer: Dry ice is solid carbon-dioxide.

Related Topics:

Sublimation: The process where a substance changes directly from a solid to a gas without becoming a liquid. Dry ice is a common example.
Carbon Dioxide (CO₂): A colorless, odorless gas that is naturally present in Earth's atmosphere. It is produced by respiration, combustion, and other processes.
Phase Changes: Transitions between solid, liquid, and gas states (e.g., melting, freezing, evaporation, condensation, sublimation, deposition).

Key Formulae and Theory:

The phase change for dry ice can be represented as:

${CO}_{2} (s) \overset{sublimation}{\to} {CO}_{2} (g)$

Where $(s)$ denotes solid and $(g)$ denotes gas.

Why it's not the other options:

It is not solid carbon monoxide (CO), which is a different, toxic compound.
It is not liquid oxygen or liquid carbon dioxide, as dry ice is specifically a solid.