What causes hot air to be hot?

What are the chemical names of these compounds? ke: mg3n2: reset next

Which of the following describes a situation where competition between producers exists

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)