Water is one of the most common and important substances on Earth. It covers about 71% of the planet’s surface and makes up about 60% of the human body. Water is essential for life, as it is involved in many biological processes and chemical reactions. Water also has some unique properties that make it different from other substances. One of these properties is its ability to change its phase, or state of matter, under different conditions of temperature and pressure.
In this article, we will explore the different phases of water and the names of the phase changes that occur when water transitions from one state to another. We will also look at some examples of incorrectly matched phase changes and explain why they are wrong. By the end of this article, you will have a better understanding of how water behaves and why it is such a fascinating substance.
Contents
What are the phases of water?
Water can exist in three main phases: solid, liquid, and gas. These phases are determined by the arrangement and movement of the water molecules, which are composed of two atoms of hydrogen and one atom of oxygen. The water molecules are held together by intermolecular forces, which are attractions between the positive and negative charges on different parts of the molecules. These forces are weaker than the bonds that hold the atoms together within a molecule, but they still have a significant effect on the properties of water.
In the solid phase, water molecules are arranged in a regular pattern called a crystal lattice. The molecules are close together and vibrate around fixed positions. The intermolecular forces between the molecules are strong enough to keep them in place. The solid phase of water is commonly known as ice.
In the liquid phase, water molecules are still close together, but they have more freedom to move around. The molecules can slide past each other and form temporary clusters, but they do not have a fixed order. The intermolecular forces between the molecules are weaker than in the solid phase, but still strong enough to keep them together. The liquid phase of water is what we usually encounter in our daily lives.
In the gas phase, water molecules are far apart and move randomly in all directions. The molecules have a lot of kinetic energy, which means they can overcome the intermolecular forces that hold them together. The gas phase of water is also known as water vapor or steam.
What are the phase changes of water?
A phase change is a physical process that occurs when a substance changes its state of matter. A phase change does not involve a change in the chemical composition or identity of the substance, only in its arrangement and movement of molecules. A phase change requires energy to be either absorbed or released by the substance, depending on whether it is going from a lower-energy state to a higher-energy state or vice versa.
There are six main types of phase changes that water can undergo:
- Melting: This is when solid water (ice) changes into liquid water. This requires energy to be absorbed by the ice to break the intermolecular forces that hold the molecules in place. The temperature at which this happens is called the melting point, which for pure water is 0°C (32°F) at standard atmospheric pressure.
- Freezing: This is when liquid water changes into solid water (ice). This requires energy to be released by the water to form the intermolecular forces that keep the molecules in a fixed position. The temperature at which this happens is called the freezing point, which for pure water is also 0°C (32°F) at standard atmospheric pressure.
- Evaporation: This is when liquid water changes into gas (water vapor). This requires energy to be absorbed by the water to overcome the intermolecular forces that keep the molecules together. Evaporation can happen at any temperature, but it is faster at higher temperatures and lower pressures. Evaporation occurs at the surface of liquid water, where some molecules have enough energy to escape into the air.
- Condensation: This is when gas (water vapor) changes into liquid water. This requires energy to be released by the water vapor to form the intermolecular forces that bind the molecules together. Condensation can happen at any temperature, but it is faster at lower temperatures and higher pressures. Condensation occurs when water vapor comes into contact with a cooler surface or air, where some molecules lose enough energy to stick together as liquid droplets.
- Sublimation: This is when solid water (ice) changes directly into gas (water vapor) without going through the liquid phase. This requires energy to be absorbed by the ice to break both the intermolecular forces that hold the molecules in place and those that keep them together. Sublimation can happen at any temperature, but it is faster at lower pressures and higher temperatures. Sublimation occurs when ice is exposed to dry air or vacuum, where some molecules have enough energy to escape into the gas phase.
- Deposition: This is when gas (water vapor) changes directly into solid water (ice) without going through the liquid phase. This requires energy to be released by the water vapor to form both the intermolecular forces that keep the molecules together and those that hold them in place. Deposition can happen at any temperature, but it is faster at higher pressures and lower temperatures. Deposition occurs when water vapor comes into contact with a very cold surface or air, where some molecules lose enough energy to stick together as solid crystals.
Now that we have learned about the phases and phase changes of water, let us look at some examples of incorrectly matched phase changes and explain why they are wrong.
- Ice melting at 100°C: This is incorrect because ice melts at 0°C, not 100°C. 100°C is the boiling point of water, which is when liquid water changes into gas (water vapor). To melt ice at 100°C, the pressure would have to be very high, about 2090 atm, which is not a common condition on Earth.
- Water evaporating at -10°C: This is incorrect because water does not evaporate at -10°C, it freezes. -10°C is below the freezing point of water, which is 0°C. To evaporate water at -10°C, the pressure would have to be very low, about 0.006 atm, which is also not a common condition on Earth.
- Water vapor condensing at 50°C: This is incorrect because water vapor does not condense at 50°C, it remains as gas. 50°C is above the boiling point of water, which is 100°C. To condense water vapor at 50°C, the pressure would have to be very high, about 12.3 atm, which is also not a common condition on Earth.
- Ice sublimating at 25°C: This is incorrect because ice does not sublimate at 25°C, it melts. 25°C is above the melting point of ice, which is 0°C. To sublimate ice at 25°C, the pressure would have to be very low, about 0.003 atm, which is also not a common condition on Earth.
- Water vapor depositing at -20°C: This is correct because water vapor can deposit at -20°C, forming ice. -20°C is below the freezing point of water, which is 0°C. At this temperature and normal atmospheric pressure, water vapor can come into contact with a very cold surface or air and lose enough energy to form solid crystals.
Conclusion
Water is a remarkable substance that can change its phase under different conditions of temperature and pressure. The phase changes of water are named as melting, freezing, evaporation, condensation, sublimation, and deposition. Each phase change involves either absorbing or releasing energy by the water molecules to break or form intermolecular forces. Some examples of incorrectly matched phase changes are ice melting at 100°C, water evaporating at -10°C, water vapor condensing at 50°C, and ice sublimating at 25°C. These are wrong because they do not match the normal conditions for these phase changes to occur on Earth.
We hope you enjoyed this article and learned something new about water’s behavior. If you want to learn more about water and other topics related to chemistry and physics, you can check out some of the sources we used for this article. Thank you for reading!
