Question

1. what is the only substance on earth that naturally occurs in all three states?
2. why is water often referred to as a universal solvent?

Explanation:

1. Water is the only substance on Earth that naturally occurs in all three states (solid - ice, liquid - water, gas - water vapor) due to its unique molecular structure and hydrogen bonding which allows it to change states within the Earth's temperature range.
2. Water is often referred to as a universal solvent because it can dissolve a wide variety of substances. Its polar nature (with a slightly positive and slightly negative end) allows it to interact with many ionic and polar compounds. The oxygen atom in water has a partial negative charge and the hydrogen atoms have partial positive charges. This polarity enables water molecules to surround and separate ions (in the case of ionic compounds) or interact with polar molecules, pulling them apart and dissolving them.

Answer:

1. Water is the only substance on Earth that naturally occurs in all three states (solid - ice, liquid - water, gas - water vapor).
2. Water is often referred to as a universal solvent because it can dissolve a wide variety of substances due to its polar nature.