In a model rocket is the oxidizer a solid liquid or gas?

In a model rocket, the oxidizer is typically a solid. Common solid oxidizers used in model rocket propellant include ammonium perchlorate and ammonium nitrate, which are mixed with a fuel to create a combustion reaction. While there are also liquid and gas oxidizers in some rocket designs, solid oxidizers are most prevalent in model rocketry due to their stability and ease of handling.