It's not possible to say definitively whether a substance will exist as a gas at ambient temperature and pressure without knowing what substance you're referring to.

Here's why:

* The state of matter (solid, liquid, gas) depends on the substance's properties: Each substance has a unique melting point and boiling point.

* Ambient temperature and pressure vary: "Ambient" can mean different things depending on location and time of year.

Here's how to determine the state of matter:

1. Identify the substance: What specific element or compound are you asking about?

2. Look up its melting and boiling points: You can find this information in a chemistry textbook or online database.

3. Compare to ambient conditions: If the substance's boiling point is below the current temperature and pressure, it will be a gas.

Examples:

* Water (H2O): At standard ambient temperature and pressure (around 20°C and 1 atm), water is a liquid.

* Nitrogen (N2): At standard ambient temperature and pressure, nitrogen is a gas.

* Mercury (Hg): At standard ambient temperature and pressure, mercury is a liquid.

Let me know if you have a specific substance in mind, and I can help you figure out its state at ambient conditions.