Water can boil and turn into vapor likewise it can freeze and turn into ice. The question is, at what temperature does water freeze? This question reminds us of our old-school revision days. How much accurate freezing point of a liquid is? Does it vary? What all factors determine the freezing point? This article will be discussing all these points.
1. At What Temperature Does Water Freeze?
The common answer we get for this question is 0 degree Celsius or 32 degrees Fahrenheit or 273.15 Kelvin. At this temperature, water changes its form to ice crystals. But there are exceptions also. It is found that water can be cooled down to -40 to -42F without freezing. Later found that at -55F water molecules can take a tetrahedron arrangement. Each molecule will be loosely bound by four others. When this happens the properties of water also vary. Like, density will decrease, heat capacity will increase, and compressibility also increases.
Below -55F only a few water molecules will exist but they can’t last long. When water becomes ice crystals, the structure changes and this change in structure determines the rate of crystallization and thermodynamics. A nucleation site is where water freezes. A nucleus is a place around which water forms crystals. In the case of pure water, changing the structure of liquid can create a nucleus. These nuclei cannot enlarge unless and until the structure of water molecules reaches that of ice.
1.1 Structure of Water
Water has two hydrogens and an oxygen atom. The atoms have covalent bonds between them. A covalent bond is one in which sharing of electrons happens. Both hydrogen atoms share an electron pair with the oxygen atom. Oxygen’s electronegativity is higher than that of hydrogen atoms.
So there is a slightly large electron density near oxygen compared to the other two atoms. This makes water take an angular bent shape. An angle of 104.5 degrees is formed between the H-O-H bond. Water molecule shows a negative polarity near the oxygen atom and positive polarity in the hydrogen atom. Thus water molecules as a whole can be considered polar.
1.2 Structure of Ice
When liquids form ice crystals, it forms a unique lattice structure. In ice water molecules adopt a three-dimensional pattern. Unlike water, each oxygen atom has four hydrogen atoms around them. These atoms form two O-H bonds along with hydrogen bonds. This arrangement gives the ice a hexagonal shape. In the hexagonal structure, there are empty spaces. These empty spaces reduce the density of ice. Hence ice can float in water.
2. Freezing Point
It can be described as a temperature at which the liquid changes its phase to solid. Water freezes at zero degrees Celsius or 32 F. There is a misbelief that when phase change happens there is a temperature change. But in fact, the energy of the system is changing. The temperature remains intact. The matter is characterized by three states. All three states have their internal energy. Internal energy is nothing but the energy of molecules present.
Water in a gaseous state has more internal energy and molecules are loosely packed. When it loses some internal energy it can become liquid again. Internal energy is further lost during freezing and thus ice forms. In ice, molecules are tightly packed and have less freedom of movement.
2.1 Equation for Freezing Point of Water
When phase change happens, no temperature variation happens. There will be only an increase or decrease in energy. When water freezes the energy is reduced. The formula for energy requirement during phase changes is given below.
Q = -(mLf)
Where,
Q = energy requirement of a system to phase change(in joules)
m = Mass of the sample(in kilograms)
Lf = Latent heat of fusion( in joules/kilogram)
The energy required to change one unit of sample from liquid to water is known as the latent heat of fusion. It is the energy required by water to crystalize.
2.2 Factors Affecting the Freeing of Water
The factors that play an important role in the freezing process are low temperatures, quantity, and size of the container. If the temperature is comparatively colder, then freezing happens faster. If you place a cup of water and a bucket of water to freeze under the same conditions then the water in the cup will freeze faster. All liquids have different freezing points. For water, it is 32 F.
Liquids like alcohol can take a much longer time to freeze because their molecules are smaller than water. Oils and other heavy liquids also take more time to freeze than water. This is because their molecules are comparatively large.
2.3 Water Freeze Faster Compared to Other Liquids
The molecular structure of water plays a role in this matter. The hydrogen bonds in water help it to crystallize faster. Water has a high boiling point also. This indicates that water molecules can be frozen faster than other liquids.
2.4 Ways to Speed Up Freezing
Heating the liquid before putting it to freeze can speed up the freezing process. Hot water freezing faster is a fact that is relevant. When hot water is used for freezing water, the water at the bottom will be thicker than surface water. Thus it can form crystals faster than cold water. Another option to speed up the freezing process is the selection of containers. Always be attentive while selecting containers. Prefer those that are made of materials like metal or glass.
2.5 Freezing Points of Different Liquids
Depending on the type of liquid the freezing point can vary. For liquid with more salt ions, the freezing point is much lower. Salt ions can prevent the proximity of molecules. When molecules can’t come closer it will take more freezing time.
3. Ice Formation
When you place an ice tray filled with water to freeze consider some factors, firstly choose an ice tray made of metals to freeze faster. Never choose ice trays having unusual sizes. Choose ice trays without dividers because they will freeze faster than those with divisions. This is because the surface area of ice cubes has a major role in freezing. After placing the ice tray inside the freezer keep it closed. Air can affect the freezing rate. Frequent openings of the freezer can increase the temperature inside the refrigerator. It can result in a delay in solid ice formation.
4. Uses of Frozen Water
Frozen water has many purposes. Below mentioned are some uses among them.
Frozen water is used in ice skating and ice hockey.
Used to bring down temperatures of machinery.
Can be used in drinks to keep things cold.
Useful in ice sculptures.
5. Facts About Water and Ice
5.1. Water
Water is one of the inorganic compounds which is considered an elixir.
It can exist in different forms like solid, liquid, and vapor.
Water is considered a universal solvent.
At 100 degrees Celsius, it can change the phase to vapor.
When cooled below 0 degrees Celsius it can change phase to solid ice.
Liquid water molecules are less close to each other which gives them the flowing property.
75% of the human body comprises water.
5.2. Ice
Ice is the solid form of water.
They are somewhat transparent and opaque at the same time.
Ice has an ordered regular crystalline lattice structure.
If impurities are present their color can change.
Less dense than water.
Ice floating over the surface of water bodies can save aquatic animals. It can prevent the cold water below from freezing.
When we take equal mass of water and ice, water will have less volume than ice.
Summary
When the water phase change occurs there happens a change in internal energy. Several factors affect the freezing point of a liquid. Temperature, size of container, and quantity are some factors among them. Water freezes at a temperature of 0 degrees Celsius or 32 F. It is also found that water can be cooled down to -40 degree Celsius without freezing. Saltwater has ions that can lower the freezing temperature. Heavy liquids also take more time to freeze compared to water. There are different ways to speed up freezing. Heating the water before putting it inside the freezer is one of the methods. Frozen water has many real-life applications like sports, arts, and industries.
FAQs
Q1. What temp does water start to freeze?
Water’s freezing point is zero degrees in Celsius scale and 32 degrees in Fahrenheit scale and 273.15 in Kelvin scale of temperature.
Q2. Can water freeze in 40-degree weather?
Colder weather can speed up the water freezing to some extent. But when ideal conditions are provided water can freeze anywhere.
Q3. Can water freeze at 50 degrees Fahrenheit?
Water’s freezing point is zero degrees Celsius or 32 degrees Fahrenheit. It is also found that water can continue in its liquid state up to -55 degrees.
Q4. Can water freeze below 32?
Water can be maintained in its liquid state up to -55 degrees. Below -55 degrees some water molecules can exist but only for a few seconds. Normally the freezing point of very pure water is 0 degree Celsius.
Last Updated on by Laveleena Sharma