What can you do to avoid overexposure to sun's rays?

What is the mass of a sample of material that has a volume of 6260 and a density of 6980 g/cm

The earliest known human ancestors are believed to have lived 3 billion years ago. True or False

Plastic, rocks, and steel are all matter. They are made of tiny particles that can't be broken down into smaller pieces. These particles are called:

An atom of aluminum has an atomic number of 13 and a mass number of 27. How many neutrons does it have?

What are some good problem statements

What do igneous rocks form from? (20pts!)

A gas at STP has a volume of 1.0 liter. If the pressure is doubled and the temperature remains constant, the new volume of the gas will be ... ?

Combustion analysis of toluene, a common organic solvent, gives 8.20 mg of co2 and 1.92 mg of h2o. if the compound contains only carbon and hydrogen, what is its empirical formula?

Why does the moon have phases? What are the four main phases of the moon? How long does it take to change from one to another?

How many atoms are in 1/2 mole of calcium