Dorothy Mary Crowfoot Hodgkin was the first to develop protein crystallography and she won Nobel Prize for that discovery ( third woman to win the Nobel Prize in Chemistry). Hodgkin confirmed the structure of penicillin but also realized the structure of vitamin B12 by x-ray crystallography analysis. She advanced the classical technique of X-ray crystallography.
The formation of a gas is a clue to chemical changes. The bubbles of gas that you observed form when an antacid is dropped into water is an example of change. ... After ice melts into liquid water, you can refreeze it into solid ice if the temperature drops. Freezing and melting are physical changes.
