Why does water phase change matter?

Water (H₂0) - the bond of two Hydrogen atoms and one Oxygen atom - is the most important chemical compound on Earth. Not only does water make up 71% of Earth’s surface but it also makes up upwards of 90% of the human body. Water is one of the few elements that can sustain all three of the phase changes at various natural temperatures on Earth, meaning that water can be a Gas, liquid, or solid on earth solely by natural causes.

Upwards of 90% of all water on Earth is stored in the ocean, but water is constantly going through a cycle called the water cycle. This cycle involves water from the ocean (liquid) being evaporated into water vapor (gas) then condensed into either snow (solid), or back into water (liquid) and precipitated back down to earth to either freeze (solid) into snow or be drained back into a water source (liquid). This cycle is a major process in keeping this planet alive, the reason that plants can grow, weather can form and mix the air in the atmosphere, and why humans live off of this amazing compound.  

Without water phase change, humans would not be who they are today and would possibly not even be here. Additionally, plants would not be what they are, and life in general on Earth would be completely different, if it were to even exist. The first forms of life were formed in liquid water, and as far as we have seen, Earth is the only planet in our universe with known liquid water on its surface. We take it for granted, but water is the most important chemical compound on this planet and without it, and its ability to change phases regularly, there is a good chance that we would not be here.

Condensation

According to the USGS water science school, Condensation is the process by which water vapor in the air is changed into liquid water. Condensation is crucial to the water cycle because it is responsible for the formation of clouds. Condensation is the opposite of evaporation in the water cycle. So how exactly does condensation occur?

The answer lies in the arrangement of the water molecules. Water molecules in the vapor form are arranged more randomly than in liquid water. As condensation occurs and liquid water forms from the vapor, the water molecules become organized in a less random structure, which is less random than in vapor, and heat is released into the atmosphere as a result.

Example: Clouds form in the atmosphere because air containing water vapor rises and cools according to the USGS. The key to this process is that air near the Earth's surface is warmed by solar radiation. However, condensation also occurs at ground level in the form of fog. The difference between fog and clouds which form above the Earth's surface is that rising air is not required to form fog. Fog develops when air having a relatively high humidity content comes in contact with a colder surface, often the Earth's surface, and cools to the dew point.

Cloud formation:

Evaporation

Evaporation is the process by which water is converted from its liquid form to its vapor form and thus transferred from land and water masses to the atmosphere. According to Michigan Environmental Education Curriculum, Evaporation from the oceans accounts for 80% of the water delivered as precipitation, with the balance occurring on land, inland waters and plant surfaces. So how does this process occur?

The answer is heat. Heat energy is required for evaporation to occur. The heat energy breaks the bonds that hold water molecules together. This is why water evaporates easily at boiling point. When the evaporation rate is equal to the rate of condensation, a state of saturation occurs. At this point, the relative humidity in the air is at 100%.

Example: According to the USGS water science school, Evaporation from the oceans is the primary mechanism supporting the surface-to-atmosphere portion of the water cycle. After all, the large surface area of the oceans (over 70 percent of the Earth's surface is covered by the oceans) provides the opportunity for large-scale evaporation to occur. On a global scale, the amount of water evaporating is about the same as the amount of water delivered to the Earth as precipitation. This does vary geographically, though. Evaporation is more prevalent over the oceans than precipitation, while over the land, precipitation routinely exceeds evaporation. Most of the water that evaporates from the oceans falls back into the oceans as precipitation. Only about 10 percent of the water evaporated from the oceans is transported over land and falls as precipitation. Once evaporated, a water molecule spends about 10 days in the air. The process of evaporation is so great that without precipitation runoff, and groundwater discharge from aquifers, oceans would become nearly empty.

Freezing

“OH MY GOODNESS! THAT LAKE OVER YONDER IS FROZEN! LET’S GO DRIVE THE CAR ON IT!!”

If you’re friends with someone who has ever said anything remotely close to the above sentence: unfriend them immediately. Reflect on the poor decision it was to be friends with someone who puts your life in danger. Then treat yourself to a slice of chocolate cake, because you are still alive. Thankfully.

If YOU have ever said anything remotely close to the above sentence: get life insurance and a helmet. You’re obviously recklessly impulsive.

Lakes are for swimming and fishing and boating and other aquatic things. Not for driving. They can crack and your car can go down and that’s a story I don’t feel like reading about. If only lakes could stay always in their nice watery form and all danger in driving on ice could be avoided. Except for that isn’t possible because the treacheries of winter like to get in the way. And that is because our happy little friend latent heat decided to go to the dark side and instead of melting things, he froze them. The audacity!

Unlike when we discussed latent heat melting the snow into a liquid it’s sort of working in reverse here. It is taking a liquid and turning it into a solid. Temperatures are dropping and then BOOM: the water reaches its freezing temperature. At this point there is no sensible heat acting on the water at the moment because latent heat doing his part. Latent heat takes energy out of the water and releases it into the environment. This causes the individual hydrogen bonds between the water molecules to hug closer to each other – obviously because it’s getting cold and they just want to stay warm. Subsequently the surrounding environment is given energy and warmed up a bit. There you have it… you’re lake is now frozen.

SMART PEOPLE PARTY FACTOID TIME: The amount of energy it takes during the phase change from liquid to solid is 80 cal/g.

That’s right, it’s just the reverse of melting. Your science friends are still probably just looking at you with the same pity in their eyes. Seriously, just walk away.

http://www.geekosystem.com/boiling-water-freezing-video/

Melting

“Colorful Colorado”. That name seems quite appropriate with the lush green landscapes in the summer, all the wildflowers and rolling plains, the Rockies reaching towards the heavens, and in the winter the vast blanket of pure white snow signaling it’s time for snowboarding (or skiing if you’re one of those). With the first fall of snow everyone on campus seems to be in a jolly good mood making snowmen and throwing snowballs or whatever it is you decide to do in the snow. Until about three days later after you’ve slipped and fallen on your rear or had an entire tree unload it’s weight in snow on top of you. By that point you’re cursing the heavens and skipping class because you refuse to walk a mile to campus and end up with squishy, wet socks again. That’s when the sudden shift of Colorado weather causing the snow to melt away becomes a miracle. Oh, the sweet warmth of the sun saving you from that pure, white hell. Is it the warmth of the sun that causes the snow to melt? Partially. That’s called sensible heat: heat that changes temperature, such as fire. But the more interesting part of melting process is this little known thing called latent heat.

Allow me to explain:

For starters, I’m sure you are aware that melting is when water goes from a solid ice or snow form to a liquid. The sensible heat changes the temperature of the snow until it reaches it’s melting point. This is the point where latent heat kicks in and a phase change occurs. You see, once the melting point is reached the introduction of heat cannot be observed any longer as a temperature change, as the temperature remains constant during the entire process of the phase change. So sensible heat doesn’t matter at this point. What latent heat is doing to cause the snow to melt into water is taking energy from the environment and transferring it to the water, which weakens the individual hydrogen bonds between the water molecules, allowing the molecules to end up in a liquid state. Because the snow is taking energy from the environment to melt, the environment around is subsequently cooled down. Nifty.

SMART PEOPLE PARTY FACTOID TIME: The amount of energy it takes during the phase change from solid to liquid 80 cal/g.

Deposition

Deposition is defined as “the process of turning Gas into a solid”. Deposition is also known as “Desublimation” because it is the opposite process as “Sublimation” which is the turning of a solid directly into a gas. In order for deposition to be possible, lots of energy must be lost in a very short amount of time, meaning that the molecules that make up the gas, which are moving very quickly, must be slowed down so fast that they don’t have time to turn into a liquid in between.

An example of deposition on Earth is how snow forms in clouds; water vapor is lifted high into the atmosphere where it is so cold that the sub-freezing air changes the moist air directly into solid ice (snow) so fast that there is no time for it to turn into liquid water in between. Another example of deposition is how frost can form at the surface of Earth. Frost is formed when warm moist air is pushed into very cold air, and the cold air causes the moisture in the air to condense very quickly into ice, when it hits solid objects, like leaves, grass, and street signs.

Deposition is also used in science to make thin film material for things such as solar panels, gas chemicals are dispersed then energy is taken from them in order to make a thin film of solid material.

Sublimation

Sublimation

Sublimation is defined as "a phase transition process from a solid to a gas without ever entering an intermediate liquid phase."

At normal pressures on Earth, the process of transitioning from a solid to a gas requires the compound to  become a liquid. However, sublimation occurs at a certain phase during a substance's triple point, which is where the three different states (gas, liquid, solid) can coexist in their respective forms. In order for sublimation to occur, the temperature and pressure must be below this triple point.

One example of sublimation in the real world is freeze-dried goods, such as meats or other food items. This process occurs by freezing the food items directly, then lowering the surrounding pressure of the air so that the water in the food item, which is frozen, can sublimate from the solid phase to the gas phase. By doing so, the food is essentially "dehydrated" but can still be consumed for up to years at a time when packaged properly.

Probably the best known example of sublimation is the solid form of carbon dioxide, also known as "dry ice." Dry ice is used in the food industry by those looking to keep items cold, without the mess or hassle of having to clean up melted ice cubes.