How would you correctly carry out a flame test, and what colour would potassium yield, and what colour would lithium yield?

Answer First a wire loop is cleaned with diluted hydrochloric acid, which is then dipped into the sample metal or solution. This is then held over an open flame and the colour emitted is observed. The colour emitted for potassium would be purple. And for lithium is red. Bonus Information for curious students - Why do different metals have different colours? When the metal is heated, the electrons are excited from a ground state energy to an excited state, the energy released when the electron goes back to the ground state is what gives the colours. The metals have different values for the difference in energy between the excited and ground state. This difference is what leads to the varying in colours.