Colligative Properties & Osmotic Pressure

In this lab experiment, half our group observed and measured osmosis using dialysis tubes that were represented as the semipermeable membrane. It is permeable to water and other small molecules but is impermeable to larger molecules such as the sucrose solution used in each of the four beakers and tubing. The other half of our group observed the tonicity of sheep blood to determine whether the blood was isotonic, hypotonic, or hypertonic. The 85 g/dL of NaCl solution was the ideal isotonic number in relation to the sheep blood cells as well as a reference to the other observations of the solutions.

Purpose: The purpose of this laboratory was to gain an understanding of the differences between the freezing points of pure solvent to that of a solvent in a solution with a nonvolatile solute, and to compare the two.

| The temperature of each solution will be taken at the start with a thermometer accurate to +/- 0.5°C, and they should all be the same temperature and will then be kept in the same room. Rather than actually controlling the temperature, the temperature was just monitored.

Introduction: The experiment's goal was to determine the freezing point of a pure solvent and the freezing point depressions of two solutions. The freezing point and the freezing point depressions were determined by graphing the temperature of the pure solvent and two solutions as they cooled and observing when crystals first formed.

The experimenters inserted a capillary tube containing approximately 2 to 3 mm of benzoic acid into a manual Mel-Temp melting point apparatus. With the Mel-Temp dial set between 3 and 4, the temperature increased at a steady rate of approximately 2° C per minute from a plateau set at 90° C. The first appearance of liquid occurred at 119° C, and the benzoic acid completely melted by 122° C giving a melting point range of 119° C to 122° C for benzoic acid. Repeating the procedure for 2-naphthol returned a melting point range of 118° C to 123° C. Next, a 1:1 mixture of benzoic acid and 2-naphthol received the same

The freezing point of the solution was -5 degrees, while the freezing point of the pure water was -3 degrees, This is a 2 degrees difference in the freezing points. This supports the hypothesis that solutions have lower freezing points. The freezing point depression is a colligative property used to calculate the molar mass of a substance. However, It was not possible to calculate the molar mass of our substance because with a home lab kit there was no weighing involved. We were still able to record and determine the freezing point of both

A similar effect leads me to my hypothesis. Boiling point elevation is, like freezing point depression, a colligative property. When cooking something on a stove at higher elevations, salt (a solute) is added to the water in order to enable the water to go to higher temperatures without boiling. The more salt is added, the higher the temperature is able to go. Knowing this, it makes sense that the largest amount of solute will lower the temperature of our chosen solvent, tert-butanol, the most.

water should be cold enough to freeze over, but it surprisingly never does(Berke 10). In

The experiment conducted was designed to discover what solutes allow for ice to melt at a faster rate.

In order for water or milk to freeze, the temperature needs to be at or below 0ºC. In order to lower the freezing point of solution, different solutes are dissolved in solvents. When a solute is combined with a solvent, such as dissolving sugar (solute) into water (solvent), a solution is formed. The process of decreasing a freezing point of a liquid by dissolving a solute in a solution is referred to as freezing point depression. The freezing point is a colligative property, which means that the freezing point depends on the number of solute particles dissolved in a solution. For example, CaCl2, which has three particles, would lower the freezing point of a solution more than NaCl would, which only has two particles (Helmenstine).

Freezing point depression is used in the world around us, such as when salt is placed onto roads during winter during which the temperature is around or right below 0ºC to prevent any precipitation that falls from freezing onto the road. When salt (NaCl) is introduced to ice, hydrogen bonds in the ice require more energy to join together. This energy is found in the form of heat energy, decreasing the temperature of the small amount of melted water surrounding the ice (Litherland) . By placing salt onto roads

During this project, there were always two large questions. How does salt affect the freezing point and how does sugar affect the freezing point? These are very broad questions and along the way, other questions will come about considering how far this topic can lead therefore in order to answer them research will have to be involved.

Introduction: Osmosis is the diffusion of water through a selectively permeable membrane. Due to the difference in concentration gradient, particles that are dissolved can go from high concentration to low concentration through a semipermeable membrane. The purpose of the investigation was to observe the effects vinegar, corn syrup, and water has on the mass of an egg. For the vinegar my hypothesis was, if the egg is placed in vinegar , then the shell will dissolve. For the corn syrup my hypothesis was, if the egg is placed in corn syrup, then the egg will form a new shell. For the tap water my hypothesis was, if the egg is placed in tap water, then the egg will stay the same.

The ice was added continuously until the temperature of the water bath dropped to 100C. The final temperature, Tf was then measured after the ice had melted completely. The latent heat of fusion of ice was then computed.

Consequently the difference between freezing and boiling is 180 degrees Fahrenheit (212-32) or 100 degrees Celsius (100-0). This means that 180 degrees change in Fahrenheit is equal to 100 degree change in Celsius, or more simply 1.8 degrees Fahrenheit equals 1.0 degrees Celsius.