A topic should have these qualities:
As you research for your speech, your topic may shift. This is perfectly fine, and it is a way to make sure your final work reflects your research.
You can create a research question in a less structured way.
A mind map is a visual and kinetic way of building a topic into a research question. You use post-it notes or scraps of paper to visually rearrange and connect your ideas.
Free association is an exercise that doesn't need to be visual. You allow your thoughts to flow freely without interruption. You later review your thoughts and select what could be used in your research question.
You can create a research question, and explore a research topic, by answering structured questions related to an initial interesting topic. These questions help you choose a scope for your research question and will help you if you need to adjust your research question in the future.
Questions are: