You need to provide more information! 25 degrees Celsius is a temperature, but to determine the state of matter, we need to know the substance we're talking about.

Here's why:

* Water: At 25 degrees Celsius, water is a liquid.

* Iron: At 25 degrees Celsius, iron is a solid.

* Oxygen: At 25 degrees Celsius, oxygen is a gas.

Let me know what substance you're interested in, and I can tell you its state of matter at 25 degrees Celsius.