Report : Chemical practicum report in Creating Ice Cream

A.  TITLE                                                   : Chemical practicum report in Creating Ice Cream "

B.  OBJECTIVES OF EXPERIMENT     : To know the freezing point and frozen point dropping solution by                                                                          applying it in Ice Cream making.

C.  DAY / PRIVATE DATE                      : Friday , April 03, 2015

D.  THEORETICAL BASIS

v The Colligative Properties of the Solution

The solution is a homogeneous mixture of two or more substances. The interaction between solute and solvent can result in the change of physical properties of the components of the solution. One of the attributes caused by the interaction between solute and solvent is the colligative nature of the solution. The colligative nature of the solution is the nature of the solution which is only affected by the amount of solute particles in the solution, and is not influenced by the nature of the solute.

The Law of Ralout is the basis for the four properties of a dilute solution called colligative nature (from another language of colligare, meaning "to collect together") because they depend on the collective effect of the number of solute particles, not on the properties of the involved particles. The four properties are:

1)     Decrease in the vapor pressure of the solution relative to the purified solvent vapor pressure.

2)     Boiling point increase.

3)    Decrease of freezing point.

4)   Symptoms of osmotic pressure.

v Decrease of Frozen Point of Solution

The freezing process of a liquid occurs when the temperature is lowered, so the distance between the particles is so close to each other and ultimately works a very strong intermolecular attraction. The presence of particles of solute will result in the movement of solvent molecules hindered, consequently to be more closer intermolecular distances required lower temperatures. So the freezing point of the solution will be lower than the freezing point of the pure solvent. The difference of freezing point due to the presence of solute particles is called the decrease of freezing point (ΔTf). The reduction of the freezing point of the solution is proportional to the product of the solution molarcity with the settlement of the solvent freezing point (Kf), expressed by the equation:

ΔTf = Kf m     or     ΔTf = Kf (n x 1000 / p)

 Where:

ΔTf = decrease of freezing point

Kf = the molal freezing drop point

N = number of moles of solvent

P = mass of solvent

The freezing point of the solution is the freezing point of the purified solvent minus its drop in freezing point or Tf = Tfa^o- ΔTf.

v Cause and Definition of Frozen Point Decline

What is a decrease in freezing point? Pure water freezes at 0 ° C, in the presence of a solute such as the added sugar into the water, the freezing point of this solution will not be equal to 0 ° C, but will fall below 0 ° C, this is what is referred to as the "freezing point drop."

So the solution will have a lower freezing point than the pure solvent. For example, the salt solution in water will have a lower freezing point than the pure solvent which is water, or the phenol solution in alcohol will have a lower freezing point than the pure solvent ie alcohol.

Why does this happen? Does the solute resist the solvent from freezing? The explanation of why this happens is easier when described from the thermodynamic point of view as follows.

For example, pure water at 0 ° C at this temperature of water is at equilibrium between the liquid phase and the solid phase. This means that the water velocity changes from liquid to solid or vice versa is the same, so it can be said to phase water and solid phase. In this condition has the same chemical potential, or in other words the energy level of both phases is the same. The magnitude of the chemical potential is affected by the temperature, so at a certain temperature the chemical potential of the solid phase or liquid phase will be lower than the other, the phase having the lower energy potential is preferably preferable, for example at 2oC the liquid phase has a higher kimi potential Lower than the solid phase so that at this temperature the water tends to lie in the liquid phase, otherwise at a temperature of -1o C the solid phase has a lower chemical potential so at this temperature the water tends to be in the solid phase.

If into pure water we dissolve the salt and then the temperature we decrease little by little, then with the cooling time slowly some of the solution will turn into a solid phase until at a certain temperature will turn into solid phase as a whole. In general, the solute preferably resides in the liquid phase compared to the solid phase, consequently in the cooling process takes place, the solution will retain its phase in the liquid state, because the energy solution preferably resides in the liquid phase compared to the solid phase. This causes the chemical potential of the solvent in the liquid phase to be lower (down) while the chemical potential of the solvent in the solid phase is not affected. Then more energy will be needed to convert the solution into a solid phase because its freezing point is lower than its pure solvent. This is why the presence of solutes will lower the freezing point of the solution. The formula for finding the freezing point of the solution is as follows:

ΔTf = Kf. M. I

Information:

ΔTf = freezing point

Δm = molalilatis solution

Kf = constant constant freezing point of solution

Do not forget to add the Van Hoff factor to the above formula if the solution in question is an electrolyte solution.

E.     TOOLS AND MATERIALS

1)     Plastic

2)    Tablespoons

3)    Water

4)   Jar

5)    Ice Stone

6)   Salt

7)    Powder flavorings

8)    Rubber

9)   Basin

F.      HOW TO WORK

1)     Preparing the Tools and Materials needed.

2)     Enter the powder into a plastic container.

3)    Beat the powder until dissolved.

4)   Tie the plastic with rubber.

5)    Break the ice cubes.

6)   Put ice cubes and salt into the jar.

7)    Insert plastic into the rock and salt.

8)    Then shake the pan ± 10 minutes.

9)   Observe the mambo ice changes.

10)  If the ice in the plastic is solid evenly then remove it from the jar

G.  DATA RESULT OF EXPERIMENT

1)   Ice cream dough after being ejected from the panic formed into ice cream that is ready to eat. With a soft texture, not solid but not too liquid.

2)  With the process of ice play on ice cubes and kitchen salt freezing ice cream happens faster.

H. DISCUSSION

Ice has an average temperature below 00 C. In this ice cream making there is the addition of salt, so that ice melting without adding heat and water formed from the melting process will also have a temperature below 00 C. This is why the addition of salt can Reducing the melting point of water, because ice can melt below its normal melting point, which is 00 C. So salt particles are the triggers of melting ice. On the other hand, smelting requires energy (absorbing heat). Well, because here the heat is not in the supply from outside, then the ice absorbs heat from itself, so the temperature becomes far down. The ice is very cold temperatures and then will absorb a lot of heat from the dough ice cream, so the ice cream dough can freeze

   I.       CONCLUSION

Ø The colligative nature of the solution is the nature of the solution which depends only on the amount of solute particles in the solution, and does not depend on the type of solute. Colligative properties of the solution include decreased vapor pressure, boiling point boost, decrease in freezing point, and osmotic pressure.

Ø The difference of freezing point due to the presence of soluble zar particles is called the decrease of freezing point (ΔTf). The freezing point of the solution is proportional to the product of solution molality with the solvent freezing solvent (Kf) settlement, expressed by the equation:

ΔTf = Kf m or ΔTf = Kf (n x 1000 / p)

Ø Normal temperature of ice and water mixture is 0oC but not cold enough to freeze ice cream. The temperature required to freeze the ice cream is -3 oC or lower. To reach the temperature it is necessary to add salt in the process of making ice cream. Salt serves to lower the freezing point of the solution. When ice is mixed with salt, ice melts and dissolves to form salt water and lowers its temperature. This process requires heat from the outside. The mixture gets hot from the ice cream dough then the result is solid ice cream as you wish. 

J. DOCUMENTATION