Chemistry

Science Fair Project

The effect of salt and sugaron the freezing point of water

Question:

How the freezing point of water is affected by the

presence of sugar or salt?

Hypothesis:The freezing point of water will be lowered when sugar or salt is added.

Materials:

-    1 packet of sugar-    1 packet of salt-    800ml of distilled water-    8 test tubes-    8 beakers-    1 basin-    Tap water-    1 freezer-    Ice cube trays-    8 thermometers-    1 digital weighing scale-    1 black marker

Mix 200g of salt into in 1 liter of water and pour the solution into ice cube trays. Place the trays in a freezer, and leave overnight. The ice will be used to form an ice bath in the basin.

The next day, label the 8 beakers and test tubes as “Salt 0.5M, Salt 1.0M, Salt 1.5M, Salt 2.0M, Sugar 0.5M, Sugar 1.0M, Sugar 1.5M and Sugar 2.0M”.

Procedure:

Label beakers

Frozen solution

Continued: Prepare 8 varieties of solution in each beaker as

described below:

a.    Salt 0.5M – Mix 100ml of water with 2.9g of saltb.    Salt 1.0M – Mix 100ml of water with 5.8g of saltc.    Salt 1.5M – Mix 100ml of water with 8.7g of saltd.    Salt 2.0M – Mix 100ml of water with 11.6g of salte.    Sugar 0.5M – Mix 100ml of water with 17g of sugarf.    Sugar 1.0M – Mix 100ml of water with 34g of sugarg.    Sugar 1.5M – Mix 100ml of water with 51g of sugarh.    Sugar 2.0M – Mix 100ml of water with 68g of sugar

Weigh salt Mixing

NOTE:Salt has a

molar mass of 5.8g per mol. Sugar has 34g per

mol.

Continued: Fill a basin with the ice cubes prepared earlier, to

create an ice bath.

Pour the solution in each beaker

into its respective test tube to the

halfway mark, or about a height

of 5 cm. Place a thermometer into

each test tube. Then, place the 8 test tubes into the ice bath.

Fill basin with prepared ice

Test tubes in ice bath

• Observe when the first ice crystals start to form, and record the temperature.

VARIABLES: Independent variable: the amount of salt

and sugar added to the solution.

Dependent variable: the freezing point of the solution.

Control variables: the temperature of the environment (room temperature), the amount of solution in each test tube, and the temperature of the ice in the basin.

Data table:

Graph:

EXPERIMENT RESULTS

Solute used

Freezing point of solution (°C)

L 0.5 mol 1.0 mol 1.5 mol 2.0 mol

Salt -1.9 -3.8 -5.8 -7.7Sugar -0.9 -2.0 -3.3 -4.5

0.5 mol 1. mol 1.5 mol 2.0 mol

-10

-8

-6

-4

-2

0

SaltSugar

Tem

pera

ture

(°

C)

Freezing point for salt and sugar solutionMolar mass of salt and sugar added

Data Analysis/ Discussion

The data shows that as we add more salt and sugar, the freezing point of water will be lower than the normal freezing point (O°C).

Also we see that salt makes the freezing point drop lower than sugar does.

Solute used

Freezing point of solution (°C)

L 0.5 mol 1.0 mol 1.5 mol 2.0 mol

Salt -1.9 -3.8 -5.8 -7.7Sugar -0.9 -2.0 -3.3 -4.5

Freezing point depression is a condition where the freezing point of a liquid is

lowered by the presence of an additive.

At the freezing point of a particular solution, the chemical potential of the solution at liquid state and solid state will be equal. Solute particles are able to dissolve only in a liquid solvent. Conversely, when

the solvent is in a solid state, solute particles cannot be dissolved. Following the same logic, adding a solute to the solvent will reduce the

chemical potential of the solution and consequently, also its freezing point.

CONCLUSION: The hypothesis that a higher salt or sugar content

in water will lower its freezing point has been proven to be true.

Water will normally freeze at 0 °C. However, seawater does not freeze at 0 °C, as the presence of salt lowers its freezing temperature to below 0 °C. The concept of freezing point depression is useful in applications where water needs to be kept liquid, especially in the use of antifreeze in combustion engines operating at freezing temperatures.

Thank you everyoneTHE END

Presented by DUCK and EliseDUC