Transcript Push a meat
Importance of Colligative Properties of solutions Colligative Properties Some physical properties of solution are affected by the concentration of solute particles Properties of solutions that depend on the number of molecules in a given volume of solvent and not on the properties or identity of the molecules. The depend on the collective effect of the concentration of solute particles present in the solution. Colligative Properties Molecular mass of a substances can be determined. Whether a solution is iso-osmotic or not can be found. The behavior of solution of electrolytes can be understood. The osmotic properties of body fluids such as lacrimal fluids and blood can be evaluated. Isotonic solutions can be prepared Properties Vapor Pressure Lowering Boiling Point Elevation Freezing Point Depression Osmotic Pressure Vapor Pressure Lowering Also, in some steam engines the cylinder can be cooled to lower the vapor pressure of the steam and create a suction on the back side of the piston to get extra power Freeze-drying is an example of vapor pressure lowering. Freeze-drying occurs because the vapor pressure of the surrounding air is lowered, causing the surrounding air to take heat from the substance which then freezes because of heat lost. Sodium chlorate and sodium nitrate are used to calibrate RH meters which is a practical application of vapor pressure lowering. These substances lower the vapor pressure to set levels so RH meters, meters that calculate humidity, can be calibrated to the correct humidity. Salt increases the boiling point of water and is an effective application of boiling point elevation. So cooks and chefs across the world will add a pinch of salt to water to cause it to boil faster because it will boil at a lower temperature. Boiling Point Elevation Cooking . It will take slightly longer to boil, since its boiling point has now been elevated. Sugar Refining An example of boiling point elevation can be seen in making homemade candies. Excessive amounts of sugar are added to water, increasing the water's boiling point. As water evaporates, the concentration of the solution increases and the boiling point is increased yet again. This continues until the right consistency for the candy is achieved. Putting salt in pasta to make it cook faster and cooking candy at home are some common examples. The higher boiling point of salt water has two important implications in cooking. First, water takes longer to come to a boil if it contains salt. Second, the temperature of the boiling water is higher. Adding salt to pasta water means it takes longer to bring it to a boil, but the pasta will cook more quickly due to the higher temperature. Freezing Point Depression Think about salting an icy road. The freezing point of the water is lowered by the salt that you add. Also it decreases in proportion to how many particles the salt dissolves into. Calcium chloride is a good choice because it dissolves into 3 particles antifreeze in the radiator. It also follows the rule of thermodynamics "salt lowers the freezing point of water" which is a true statement as it stands by itself. Magic Salt on Icy Road Ice Cream using Cream Salt Antifreeze on Car Radiators Easily to Cold Soda/etc Osmotic Pressure The most used example is that of turgor pressure in plants. The dissolved substances in the plant cells pull water into the plant cells and keep them "inflated", which keeps the cell walls rigid and the plant doesn't "wilt". However, there is more to the process than that and osmotic pressure alone cannot account for water moving up all the way to the top of a 150 foot tree. It's much more complex than that. osmotic gradients are a way for cells to control the flux of small molecules and fluid into and out of the cell. sweating is largely dependent on osmotic pressure. Osmotic pressure is used in water filtering. Instead of regular osmosis where solvents will go from a solution of higher concentration to lower it does the reverse therefore filtering the impurities out of water. a process commonly used to purify water it determines how hard and how fast osmosis will occur. cell survival Hypertonic or Hypotonic The osmotic properties of body fluids such as lacrimal fluids and blood can be evaluated. Osmotic pressure is what keeps plants standing upright. Water presses against cell walls and the cell walls push back against the water. When equilibrium of pressures is reached, the plant remains un-wilted. Osmosis is a very useful process. For example, meats can be preserved by turning them into jerky: The meat is soaked in a very concentrated salt solution, resulting in dehydration of the meat cells. Jerky does not spoil as quickly as fresh meat, since bacteria on the surface of the salty meat will fall victim to osmosis, and shrivel up and die. This process thus extends the life of the meat without the use of refrigeration.