When liquids freeze, they transform from being a liquid to being a solid in a certain sense to describe it, the usual freezing temperature of liquid is when it reaches  0 degrees C(Celsius), 32 degrees F(Fahrenheit), or 273.15 K (Kelvin). When a liquid is freezing it will shrink, or in other words, minimize (get smaller) in size. Liquids shrink because the particles they contain are growing closer together and are not moving any longer because they are not as capable of fighting the force that attracts them to one another. When they shrink, they gather together and form a shape like a hexagon. These particles that grow close together are also called crystalline solids. “When liquid water is cooled, it contracts like one would expect until a temperature of approximately 4 degrees Celsius is reached. After that, it expands slightly until it reaches the freezing point, and then when it freezes it expands by approximately 9%” (FAQ, 1).  
The process of water expanding when freezing occurs, happens in the structure of the water molecule. Water molecules are made up of two hydrogen atoms and one oxygen atom. The oxygen atoms are more electronegative, and the hydrogen particles have a partial positive charge to it whereas oxygen particles have a partial negative charge (Structure, 1).  "This separation of charge produces a net dipole moment on the molecule; for the isolated water molecule this dipole moment is approximately 1.85 Debye units." (Structure, 1). The center of the hydrogen atom is always .0957nm (Nanometer) from the center of the oxygen atom. All of the atoms of the water particle equal an angle of 104.5 degrees. 
 The molecular structure is also commonly or scientifically known as hydrogen bonding. A hydrogen bond is a weak force that helps to form an exceptional attraction. "This happens when a hydrogen atom bonded to a strongly electronegative atom exists in the vicinity of another electronegative atom with a lone pair of electrons," (Hydrogen, 1). The bonds will mainly be stronger than an ordinary dipole-dipole. “Dipole-Dipole forces are attractive forces between the positive end of one polar molecule and the negative end of another polar molecule,” (Purdue, 1). An example of a polar molecule is water.  Water is an example of a polar molecule because it has a very small positive charge on one side/end and a slightly negative charge on the opposite side/end. These are yet weaker than covalent and ionic bonds. A covalent bond is a bond between atoms sharing electron pairs. An ionic bond is an electric bond between two ions that formed from the transfer of a certain number of electrons. Electrons are a negatively charged particle that surrounds and atoms nucleus (Jefferson,1). A nucleus is the center and genually the most important part of something. The nucleus is the part that forms the basic things that something needs for growth or even activity.  
An open solid structure causes ice to have less mass that water, or a liquid, does. This statement is the reason why ice floats above water. If water behaved as what we call quote-on-quote normal, than all bodies of water, like oceans, lakes, rivers, etc., would not just only freeze at the top layer, but it would freeze completely solid. If all of these forms of water were to freeze, we would lose the many natural resources and species that live in them. “Water's "density maximum" is a product of the same phenomenon,” (Water, 1). Close to the freezing point, the water molecules start to arrange locally into ice-like structures. This creates some "openness" in the liquid water, which tends to decrease its density. “This is opposed by the normal tendency for cooling to increase the density; it is at approximately 4 degrees Celsius that these opposing tendencies are balanced, producing the density maximum,” (Water, 1). 
In 1963 a Tanzanian student made a discovery to change the thought on the process of freezing water. This student is now known to be Erasto Batholomeo Mpemba. He discovered the Mpemba effect.  The Mpemba effect is the scientific proven rule that water then has a higher temperature (warm water) freeze faster then water with a lower temperature (Edwards, 1). “It was first noted in the fourth century BC by Aristole, and many scientists since have noted this phenomenon,” (Edwards, 1). It was never actually labeled under anything until “Erasto Batholomeo Mpemba made the statement in his science class that ice cream would freeze faster if it was heated first,” (Edwards, 1). His classmates ridiculed him until a teacher at the school experimented the  statement and found it to be true (Edwards, 1). It is also said this rule only applies under certain circumstances. He shows that water with a higher temperature has a faster evaporation rate, which means less mass to freeze. He also showed that on cold water there is a frost layer that acts as an insolation.   
One thing that is also very commonly thought about why the Mpemba effect is scientifically true is that certain concentration of solute, for example carbon dioxide, is minimized when water gains a higher temperature, when it is warmer (Edwards, 1). “Carbon dioxide is a colorless, odorless gas found in our atmosphere, our bodies, and found in many other places,” (Study, 1).  There is nothing proven to show that when they say  freezing or frozen whether it means when a layer freezes over or when all of the liquid turns to a solid block of ice. A scientist named James Brownridge has been studying this effect. He says that the warmer water may freeze faster because of the difference is temperature from the freezer. “  This helps it reach its freezing point before the cold water reaches its natural freezing point, which is at least 5 degrees C (Celsius) lower,”   (Edwards, 1).