Please help me if you can. Please explain how you got the answer thank you.

Avariable that is not being directly tested during an experiment should be changed varied experimented controlled

Why is the melting of ice a physical change ?

Observation and experimentation have led many scientists to accept a theory about the origin of the universe. this theory is called the big bang theory. scientific evidence collected and observed by scientists around the world suggests that the universe is ever expanding from a hot and dense initial state. what makes this a scientific theory? (2 points)