Boiling : Boiling Use these hints to help answer your questions. Vapor pressure : Free powerpoint template: www.brainybetty.com 2 Vapor pressure - The pressure of the gaseous phase (vapor) coexisting with the liquid or solid phase of a substance.
The easier it is to evaporate, the higher the vapor pressure will be
The higher the temperature, the higher the vapor pressure will be Boiling : Free powerpoint template: www.brainybetty.com 3 Boiling -Bubbles of vapor forming in the liquid phase. This happens when the vapor pressure is equal to the air pressure on the liquid
Boiling point - the temperature at which the vapor pressure is equal to the atmospheric pressure Standard Pressure : Free powerpoint template: www.brainybetty.com 4 Standard Pressure - air pressure of dry air at sea level.
760 torr (mm Hg)
101.325 kilopascal (kPa)
1 atmosphere (atm)
Normal boiling point - the boiling point at standard pressure Normal Boiling Point of Water : Free powerpoint template: www.brainybetty.com 5 Normal Boiling Point of Water Normal bp of water
Remember this is at average pressure at sea level
212oF Boiling Point in Pgh : Free powerpoint template: www.brainybetty.com 6 Boiling Point in Pgh You know water runs downhill, right?
If the Allegheny River runs into the Ohio River that runs into the Mississippi River, that is all downhill to the ocean in the Gulf of Mexico.
FYI - some places, Death Valley for instance, can be below sea level and dry Boiling Point in Pgh : Free powerpoint template: www.brainybetty.com 7 Boiling Point in Pgh Air pressure is caused by the air above the place in atmosphere.
As the amount of air over something becomes less, the air pressure gets smaller.
As you go up in elevation, the air pressure gets lower.
The air pressure in Pittsburgh should be lower than at sea level. Boiling Point in Pgh : Free powerpoint template: www.brainybetty.com 8 Boiling Point in Pgh The boiling point of water in Pittsburgh should definitely be lower than 100oC. Boiling Point and Pressure : Free powerpoint template: www.brainybetty.com 9 Boiling Point and Pressure The lower the air pressure is the lower the boiling point of the liquid becomes.
The reverse of that is true also.
Boiling point can change dramatically depending on the air pressure. Kinetic Theory Explanation : Free powerpoint template: www.brainybetty.com 10 Kinetic Theory Explanation The Kinetic Theory explains everything in terms of the particles in materials.
The fewer air particles pushing on the surface of the liquid, the easier it is to form bubbles inside the liquid. Therefore, the less energy it takes to form the bubbles. So, the lower the temperature has to be to create the energy. Pressure and Boiling Point : Free powerpoint template: www.brainybetty.com 11 Pressure and Boiling Point Denver is in the Rocky Mountains.
Denver is called the “Mile High City”
The air is thin in the mountains, like you find around Denver. Pressure and Boiling Point : Free powerpoint template: www.brainybetty.com 12 Pressure and Boiling Point If the air is thinner, what happens to the air pressure on liquids in Denver?
If the air pressure is lower, what happens to the boiling point. Pressure and Boiling Point : Free powerpoint template: www.brainybetty.com 13 Pressure and Boiling Point The boiling point of water is lower in Denver.
That means that because it is easier to boil the water in Denver, the water is not as hot as you think.
The water gets stuck at the cooler boiling point so it takes longer to cook pasta or rice in the water. Uses of Lowering Boiling Point : Free powerpoint template: www.brainybetty.com 14 Uses of Lowering Boiling Point Milk scorches at a particular temperature and boils at a temperature higher than that.
By boiling the milk in a vacuum, it decreases the boiling point to below the scorch temperature.
Look at this description of the invention of evaporated milk Vacuum Cooking : Free powerpoint template: www.brainybetty.com 15 Vacuum Cooking Norbert Rillieux
born into an aristocratic Creole family in New Orleans, Louisanna
son of Vincent Rillieux, a white plantation owner, and Constance Vivant, his placee (common-law wife of different race). Vacuum Cooking : Free powerpoint template: www.brainybetty.com 16 Vacuum Cooking early part of the 1800s sugar refinement was slow, expensive, and inefficient.
Sugar cane juice was pressed and extracted from the cane Vacuum Cooking : Free powerpoint template: www.brainybetty.com 17 Vacuum Cooking Workers poured the sugarcane juice into the largest kettle
it was heated
most of the water evaporated
They continued to pour the resultant thick liquid into smaller and smaller pots
the liquid continued to thicken
sugar crystallized. Vacuum Cooking : Free powerpoint template: www.brainybetty.com 18 Vacuum Cooking Sugar was lost in transfer
Sugar was burned during evaporation
The process was dangerous for the workers, who routinely had to transfer the hot liquid. Vacuum Cooking : Free powerpoint template: www.brainybetty.com 19 Vacuum Cooking Rillieoux invented a system utilizing a vacuum chamber or a container with reduced air to lower the boiling point of the liquids.
Used lower temperature
Sugar didn’t burn
Safer for workers Vacuum Cooking : Free powerpoint template: www.brainybetty.com 20 Vacuum Cooking Gail Borden also discovered ways of condensing products
Secured patents for his condensed milk vacuum cooker in 1851
Led to creation of Borden, Inc. in 1854 Vacuum Cooking : Free powerpoint template: www.brainybetty.com 21 Vacuum Cooking successful promotion of his condensed milk
not until the Civil War
troops needed milk products that did not spoil Raising Boiling Point : Free powerpoint template: www.brainybetty.com 22 Raising Boiling Point If liquids like water or milk boil at a lower temperature when placed in a vacuum, how can the temperature be raised? Raising Boiling Point : Raising Boiling Point If lowering pressure decreases the boiling point, than increasing pressure will increase the boiling point.
Water will boil at a higher temperature at a higher pressure.