Вместо пропусков вставьте необходимые по смыслу предлоги:
every substance has a melting point and a boiling point. the former is the temperature which it changes solid liquid. the latter is the temperature it changes liquid gas. these changes are called changes . sometimes the properties a substance change when it changes its state. example, if the temperature oxygen falls below -183 c, it changes a colourless gas a bluish liquid, which is highly magnetic.