That's a physical change. There are no chemicals reacting with each other, it's the simple presence of concentration of food colouring and oil in water that changes its appearance.
Work, for example is the subject of an entire branch of psychology. psychological, behavioural, emotional, and social factors.
The Boston massacre was a street fight it went from throwing snow balls to rocks and other objects several colonists were killed and this led to a campaign by speech writers to rouse the ire of the citizenry
Working together between countries
