In a chemical equation, what do the coefficients represent?

What is the name of the massive cloud of gas and dust from which a star and its planets form?

What is the chemical formula for ammonia?

What is the term for the process by which water returns to the Earth's surface from the atmosphere in the form of rain, snow, sleet, or hail?

What force opposes the relative motion or tendency of such motion of two surfaces in contact?

Which celestial event occurs when a planet appears to reverse its normal direction of motion in the sky?

What is the term for the point on the Earth's surface directly above the earthquake's origin, where seismic waves are first felt?

What is the process of a substance changing from a gas to a liquid called?

Which layer of the Earth's atmosphere is characterized by decreasing temperature with altitude and contains the ozone layer?

What law of motion states that for every action, there is an equal and opposite reaction?