1. Introduction

This project aims to test whether temperature, salt and sugar affect the speed of the initial freezing of pure water.To solve this question,we will use a mixture of ice and salt,to be put into a styrofoam box(10cm x 10cm x 12cm).We will then use a temperature probe to measure the temperature of the water in the test tube.Using the probe and the data logger,we will then record the data down in a spreadsheet and then plot a graph for each temperature or amount of salt or sugar. We found out that most of the time, salt freezes faster than sugar. However, 1g of sugar started to freeze faster than 4g of salt.3g and 4g of sugar did not manage to start freezing in 3 minutes.Pure water(Control) did not manage to freeze within 3 minutes.60 degree of water froze faster than 65 degree of water.However,both 60 degree of water and  65 degree started freezing within 3 minutes.This is useful for the reader to be able to find out on whether they should pour salt they should put should they want to chill something really quickly. The reader could also consider heating up the items they want to chill before chilling them.This can help reduce the electricity bills of the person by reducing on the use of the freezer.

Table of Contents

1. Temperature of Water

2. Conduction
3. Convection Heat
4. Heat Transfer
5. SuperCooling
6. Evaporation
7. Phase Change
8. Mpemba Effect
9. Effect of sugar on the freezing point of water
10. Effect of salt on the freezing point of water

Temperature of water

The temperature of water in a container is the average energy of its molecules. The amount of heat in the water is defined as the the total amount of energy of all its molecules. The amount of water and the number of its molecules in the container affects the amount of heat.

When placing a container of water in the freezer compartment of a refrigerator, the water will cool down and finally freeze. As the thermal energy of the water molecules goes down, the temperature of the water also goes down. When the temperature reaches its freezing point of 0 Degree Celsius and starts changing from a liquid to a solid state.

The freezing point of 0 Degree Celsius will remain until the water solidifies. After the water the water turns into a solid state, its temperature can become lower if the surrounding temperature is lower.(SchoolforChampions,2015)

Mpemba effect
If hot water was placed in the freezer in small container which is a good conductor of heat, the heat will melt the frost that is formed outside the container, which includes the ice on the bottom surface. It creates a good connection between the container and the surface, allowing a better conduction than a container that contains cold water when the ice refreezes. Just as a layer of frost on the surface of a container can slow down the conduction of heat from the water. Even a layer of ice on the upper surface of the water can insulate the water from the colder air currents, slowing the freezing process. When the water reaches between 3 and 0 degree Celsius, it will float to the surface as it is less dense the unfroze water, acting as a insulator that protects the water below from freezing which will slow down the freezing process of water. In the case of warm water, the convection currents will cause that layer of ice to melt, allowing the water to cool more rapidly.
Evaporation in the case of warm water allows it to freeze faster than cold water as there is more evaporation from the warm water than in the cold water. Not only it does carry some of the water, it also allows the amount of water to freeze in the warm water container which will in fact decrease the temperature of the warm container due to heat loss. A poor conductor of heat (Wood) is a great part of cooling as it will be cause by evaporation instead of conduction. This is an important factor in explaining how hot water freezes faster than cold water. [Mpemba used wooden buckets when he was making his ice cream and noticed the phenomenon.]
Gases is one more possible factor that concerns as water always contains dissolved oxygen and carbon dioxide. These impurities have the effect of lowering the freezing point of water. When the water is heated, gases are driven out because of their solubility in water is less at higher temperatures. Thus when the hot water cools, the higher freezing point of the less dissolved gas than water and freezes first.
One other factor may be the environment.The initially hot water may change the environment around it in some way that makes it cool faster later on. The size of the freezer that the container sat in is important.
One of the factor is of the non-uniform temperature.The hot water rises to the top and displacing the cold water beneath it is also known as convection current. These currents are popular form of heat transfer in liquids and gases, which occurs in the ocean and also in the radiators that warm a chilly room. The uneven temperature distribution creates convection currents that accelerate the cooling process. The temperature of the hotter water can drop at a faster rate than the cooler water.(SchoolforChampions,2015)

Heat conduction is the flow of the internal energy from a region of higher temperature to one of lower temperature by the interaction of the adjacent particles (atoms, molecules, ions, elections,etc.) in the intervening space.
It is also defined as heat transfer by means of molecular agitation within a material without any motion of the material as a whole. The energy of the hotter end of a metal rod will be transferred down towards the colder end due to the collision of the higher speed particles with the slower ones and a net transfer of energy to the slower ones.
In conduction, Thermal energy can move through a substance. Usually metals are good conductors of heat, but on addition, non-metals and gases are usually poor conductors of heat. Insulators are known as a poor conductor of heat. Heat is conducted from the hotter end of an object to the colder end. [ There is no such thing as more colder or less colder. It is the small amount of higher speed molecules than the slower ones.]
The electrons in a piece of metal can leave their atoms and move about in the metal as free electrons. [Link: That is why metals are also a good conductor of electricity as free electrons are able to pass electric current much faster than poor conductor of electricity.]  Charged metal ions are parts of metal atoms left behind. The ions are packed closely together and they vibrate continually. As the metal gets hotter, the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of the metal to cooler parts by the free electrons. These ions move through the structure of the metal, colliding with the ions as they go.(PhysicsInfo,2015)

Convection is the transfer of energy through the movement of currents of a gas or liquid.It is also defined as heat transfer within a material without any motion of the material itself.If one end of a metal rod is at a higher temperature, then energy will be transferred down the rod toward the colder end because the higher speed particles will collide with the slower ones with a net transfer of energy to the slower ones.Convection of mass cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids.Convection can be demonstrated by placing a heat source (e.g. a Bunsen burner) at the side of a glass full of a liquid, and observing the changes in temperature in the glass caused by the warmer fluid moving into cooler areas.
The particles in fluids can move from place to place. Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection.
Liquids and gases expand when they are heated. This is because the particles in liquids and gases move faster when they are heated than they do when they are cold. As a result, the particles take up more volume. This is because the gap between particles widens, while the particles themselves stay the same size.(HyperPhysics,2015)

Heat Transfer
The discipline of heat transfer is concerned with only two things: temperature, and the flow of heat. Temperature represents the amount of thermal energy available, whereas heat flow represents the movement of thermal energy from place to place.
On a microscopic scale, thermal energy is related to the kinetic energy of molecules. The greater a material's temperature, the greater the thermal agitation of its constituent molecules (manifested both in linear motion and vibrational modes). It is natural for regions containing greater molecular kinetic energy to pass this energy to regions with less kinetic energy.Several material properties serve to modulate the heat tranfered between two regions at differing temperatures. Examples include thermal conductivities, specific heats, material densities, fluid velocities, fluid viscosities, surface emissivities, and more. Taken together, these properties serve to make the solution of many heat transfer problems an involved process.(efunda,2015)

is a process of the lowering of the temperature of a liquid or a gas below its freezing point without it becoming a solid. A liquid crossing its original freezing point will crystallize with the presence of seed crystals or nuclei around which a crystal structure can form creating a solid. Lacking any such nuclei, the liquid phase can be maintained all the way down to the temperature at which crystal homogeneous nucleation occurs. Homogeneous nucleation can occur above the glass transition temperature, but if homogeneous nucleation has not occurred above that temperature a non-crystalline solid will form.

Water normally freezes at 0°C  but it can be "supercooled" at standard pressure down to its crystal homogeneous nucleation at almost −48.3 °C.The process of supercooling requires water to be pure and free of nucleation sites, which can be achieved through processes like reverse osmosis, but the cooling itself does not require any specialised technique. If water is cooled at a rate on the order of 10^6 K/s, the crystal nucleation can be avoided and water becomes a glass.(C.Austin,2008)

Evaporation happen to cold and warm liquids,but happens more frequently to warm liquids and it is all about the energy in individual molecules, not about the average energy of a system. The average energy can be low and the evaporation still continues evaporation happens when atoms or molecules escape from the liquid and turn into a vapor. Not all of the molecules in a liquid have the same energy. When you have a puddle of water (H2O) on a windy day, the wind can cause an increased rate of evaporation even when it is coldEvaporation from the oceans
One factor of evaporation would be if the air is saturated with substances.If it already saturated with substances,liquid would not be able to evaporate as quickly.If the humidity is 100%,the air is saturated with water and no more water can evaporate.
Air pressure also affects evaporation. If air pressure is high on the surface of a body of water, then the water will not evaporate easily. The pressure pushing down on the water makes it difficult for water to escape into the atmosphere as vapor. One real life example of high air pressure would be storms.Storms are often high-pressure systems that prevent evaporation.
One other factor of the rate of evaporation would be temperature. Boiling-hot water will evaporate quickly as steam.(chemforkids,2015)

Phase Change
Phase change is defined as the transitions between solid, liquid, and gaseous phases typically involve large amounts of energy compared to the specific heat. If heat were added at a constant rate to a mass of ice to take it through its phase changes to liquid water and then to steam, the energies required to accomplish the phase changes would lead to plateaus in the temperature vs time graph.(Hyperphysics,2015)(Homework Assignment Help,2015)

The presence of sugar (or salt, or any other dissolved substance in water) does indeed lower the freezing point of water. This phenomenon, called freezing point depression, occurs because the particles of the dissolved substance interfere with the formation of the crystalline bonds between water molecules that give ice its solidity.
Interestingly, the addition of a solute (dissolved substance) to water not only lowers the freezing point but also raises its boiling point — a phenomenon referred to as boiling point elevation. It does this by lowering the vapor pressure of water (a tendency that describes a substance's tendency to turn into a gas).(Infoplease,2015)

The salt dissolves into the liquid water in the ice and lowers its freezing point.If you ever watch salt melting ice, you can see the dissolving process happen -- the ice immediately around the grain of salt melts, and the melting spreads out from that point.
When salt (sodium chloride or NaCl) dissolves in water, each molecule separates into sodium (Na+) and chlorine (Cl-) ions, which mix separately among the water molecules. These ions affect the water molecules and their freezing and boiling temperatures in different ways. Water molecules form crystals when they freeze. But when there is salt in the water, the Na+ and Cl- ions get in the way of the water molecules, making it more difficult for them to rearrange into crystals. This means that, when compared to plain water, salt water remains in a liquid state for a longer amount of time as the temperature decreases. As heat is added to plain water, the temperature rises and the water molecules gain more energy. They move around faster and collide with each other more often. At the boiling point, the water molecules have enough energy to escape the liquid. (In technical terms, the vapor pressure of the water molecules is greater than the surrounding atmospheric pressure. In salt water, the Na+ and Cl- ions dilute the water, isolating each water molecule somewhat from others. This means that each molecule will need more heat energy to move around and collide with other water molecules than is the case for pure water. In turn, this means that the salt water will have to be at a higher temperature for the water molecules to escape by boiling.(Planetseed,2006)

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