States of Matter

Water in the oceans absorbs heat energy from the sun and changes from a liquid state into water vapor, which is a gas. This process of a liquid turning into a gas at its surface is called evaporation.

Clouds form when rising water vapor cools down high in the atmosphere and changes back into tiny liquid water droplets or ice crystals. This transition from gas to liquid is known as condensation.

Boiling is a rapid phase transition from liquid to gas that occurs throughout the liquid. During this process, the particles absorb heat energy, move faster, and eventually gain enough kinetic energy to overcome the attractive forces holding them together as a liquid.

Warm, moist air from the shower comes into contact with the cold surface of the window. This causes the water vapor in the air to cool down and turn back into liquid water droplets on the glass, which is called condensation.

When wet clothes dry, the liquid water trapped in the fabric absorbs heat from the surrounding air and sun, turning into water vapor (a gas) and escaping into the air. This process is called evaporation.

Boiling is a physical change where a liquid turns into a gas throughout the entire volume of the liquid, not just at the surface. This rapid phase change causes bubbles of vapor to form within the liquid and rise to the top.

Evaporation is the process where a substance in a liquid state changes into a gaseous state. Condensation is the reverse process (gas to liquid), and solidification is liquid to solid.

Solidifying (or freezing) is the phase transition in which a liquid turns into a solid when its temperature is lowered below its freezing point. Melting is the opposite process, where a solid becomes a liquid.

When a solid melts into a liquid, it absorbs thermal energy from its surroundings. This causes the particles to gain kinetic energy, vibrate more rapidly, and eventually break free from their fixed positions.

Melting is the physical process where a solid absorbs heat and transitions into a liquid state. Freezing and solidifying refer to the reverse process of a liquid becoming a solid.

Snow is a solid, white crystalline form of water that precipitates from the atmosphere under freezing conditions. Sugar, salt, and baking powder are not made of water molecules.

Water is highly unusual because it expands upon freezing. This occurs because hydrogen bonds form a crystalline lattice structure in ice that keeps the molecules further apart than they are in liquid water.

A phase change from liquid to gas does not alter the chemical identity of a substance. Therefore, water vapor has the exact same molecular formula as liquid water, which is H2O.

The vast majority of Earth's water is found in the oceans, which are composed of liquid water. Only a small fraction exists as solid ice in glaciers or as water vapor in the atmosphere.

Water is a polar molecule because of the unequal sharing of electrons between the highly electronegative oxygen atom and the hydrogen atoms. This creates a partial negative charge near the oxygen and partial positive charges near the hydrogens.