When a substance changes its phase of matter, is that a chemical or physical change?

Reaction rate depends on how many molecules are coming into contact with each other with enough energy to react. increasing the temperature of the reactants will increase -

Which of the following would be an accurate picture of the earth during the summer time of the northern hemisphere?

How does the atmosphere to make earth livable? check all that apply. causes the seasons contains oxygen provides warmth creates important nutrients blocks harmful energy from the sun plz like !