How to change the category?

click on edit and you can change it 

Go to your Question click on Edit then click Edit Category from there you can Select a New Category for your Question to go In 

Moving your question can be done by clicking Edit (pencil icon for mobile)>Edit category just beneath your question, then selecting the category that's appropriate for the topic

If you post a question go to your question, click 'Edit' and then select 'Edit Category'. You will see a list of categories and can move it where you want it.

Click on "edit" and you will see an option to change the category. You can then select a new category from the menu. I suppose Science & Technology > Chemistry would be the most appropriate category for your question.