👉 Expellant is a substance that can emit heat, light or both when it interacts with matter. It's often used in physics and chemistry to describe objects that absorb or release energy, such as a charged particle, an ion, or a molecule. For example: - Gas: A gas has no definite volume and is always at its maximum density. When you add a gas, it expands and becomes more dense, which results in heat and light being emitted. For example, when you blow hot air
