Lab report boiling point

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  • Publicado : 9 de octubre de 2010
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PURPOSE

This science experiment is being done on boiling point elevation, or the law that says adding solutes to solvent increases its boiling point. In this experiment, various amounts of saltwill be added to water and the change in boiling point will be observed.

INTRODUCTION

The fact that dissolving a salt in a liquid, such as water, affects its boiling point comes under the generalheading of colligative properties in chemistry. In fact, it’s a generic phenomenon dissolve one substance (the solute) in another (the solvent) and you will raise its boiling point.

Colligativeproperties determine how a solvent will behave once it becomes a solution, as it were. The degree of change depends on the amount of solute dissolved in the bulk liquid, not the type of solute. So,here’s a rough explanation of what’s going on. If a substance has a lower vapor pressure than the liquid, then dissolving that substance in the liquid, common salt in water, for instance, will lower theoverall vapor pressure of the resulting solution compared with the pure liquid. A lower vapor pressure means that the solution has to be heated more than the pure liquid to make its molecules vaporize. Itis an effect of the dilution of the solvent in the presence of a solute.

Put another way, if a solute is dissolved in a solvent, then the number of solvent molecules at the surface of the solutionis less than for pure solvent. The surface molecules can thus be considered “diluted” by the less volatile particles of solute. The rate of exchange between solvent in the solution and in the airabove the solution is lower. A lower vapor pressure means that a higher temperature is necessary to boil the water in the solution, hence boiling-point elevation.

MATERIALS

• Water

•Table Salt

• Thermometer

• Beakers

• Heat

• Timer

• Teaspoon

PROCEDURE

1. Label four beakers 1,2,3, and 4.

2. In beaker #1, add 5g of table salt. In...
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