Properties of Solutions Flashcards
Polarity of Water I
Water has several unique properties. It is a polar molecule and has a negatively charged (oxygen end) and positively charged (hydrogen end) sides. The polarity of water allows it to form hydrogen bonds and demonstrate both cohesive and adhesive properties.
Osmosis
A specific type of diffusion in which water moves across a semipermeable membrane from an area of high concentration to an area of low concentration.
Cohesion
Is a measure of how well similar molecules stick to each other or group together. Water molecules are cohesive because they are attracted to other water molecules. The cohesiveness of water allows it to travel through small capillaries without using energy. Cohesiveness also creates surface tension by creating tight-knit layer of water molecules on the surface of any body of water.
Water Polarity II
Breaking up multitude of hydrogen bonds between water molecules requires a lot of energy, so water is said to have a high specific heat and high heat vaporization. Water boils at 100 degrees Celsius or 212 Fahrenheit. Ice floats on water because it has a lower density than liquid water. Most substances have greater densities in solid form. Water is also considered the universal solvent meaning many substances dissolve in water.
Adhesiveness
The measure of how well dissimilar particles or surfaces cling to one another. The adhesiveness of water allows it to stick to other molecules because of water’s polarity
Solvent
The substance in which a solute is dissolved to form a solution. Water is considered the Universal solvent meaning many substances dissolve in water.
Solvents and Solutes
The formation of a solution from a solute and a solvent is a physical process, and it does not involve any chemical transformation. A solution is formed when a liquid mixture consisting of one or more solutes dissolves in a solvent. The solvent constitutes a greater proportion of the solution than the solute.
Solution
A solution is formed when a liquid mixture consisting of one or more solutes dissolves in a solvent. The solvent is in a greater proportion of the solution than the solute. Solutions exist as gases, liquids and solids. The overall phase of the solution is the same phase as the solvent. So if the solvent is a liquid and the solute is a solid, then the solution will be liquid.
Solubility of a substance
determined by intermolecular interactions.
Solutes
The substance dissolves in a solvent to form a solution. Solutes are hydrophilic (water-loving) or hydrophobic (water-fearing).
Hydrophilic Solutes
Have substantial consequences in biological systems. Vitamins with hydrophilic structures are water-soluble.
Hydrophobic solutes
Have substantial consequences in biological systems. Vitamins that are hydrophobic are fat-soluble.
Solid & Liquid Solutes
Solubility of most solid and liquid solutes increases with increasing temperature.
Gas Solubility
Solubility of gas decreases with increasing temperature.
Saturated Solution
A solution containing the maximum possible amount of solute.
Unsaturated solution
When less than the maximum amount of solute is dissolved.
Supersaturated solution
A solution that has been raised to a higher temperature in order to dissolve more solute than would be possible at room temperature or lower temps.
Concentration of a Solution
The quantity of solute in a given quantity of a solution.
Dilution
Is the addition of solvent, which decreases the concentration of the solute in the solution. Different units are used to express the concentrations of a solution depending on the application.
Unit concentrations of a solution
1.Molarity= mol/L
2.Mole Fraction = mol/mol
3.Molality= mol/kg
4.Mass Percentage= mass solute (g)/mass solution(g) X 100
5.Parts per thousand (ppt) = g solute/kg solution
6.Parts per million (ppm) mg solute/kg solution
7. Parts per billion (ppb)=mcg solute/kg solution
*Units of ppb or ppm are used to express very low concentrations, those of residual impurities in foods or pollutants in environmental studies. Molarity of a solution is temperature dependent, but other units are independent of temperature.
Osmosis & Diffusion
These are key processes for the transport of molecules through substrates and across membranes. Diffusion and Osmosis do not require energy, other than kinetic energy moving molecules. This is called passive transport.
Diffusion
Diffusion is the movement of any substances from areas of high concentration to areas of low concentration. Ex: Perfume is sprayed and concentrated in one area and overtime molecules spread out in all areas of the room. Ex: Blood in capillaries moving from heart to lungs in high concentrations of carbon dioxide. CO2 will move out of capillaries and diffuse across respiratory membrane into the air of the lung alveoli. This decreases CO2 in blood . Air in lungs is rich with CO2 is then exhaled.
Osmosis
Osmosis is a specific type of diffusion referring to water moving from an area of high concentration to low concentration. Water moves passively across a membrane through pores made of proteins called aquaporins. Water is a solvent, meaning substances (solutes) dissolve in it. Water moves in regions where solvent concentration is high to where solvent concentration is low. Ex: Plants take up water through their roots. Osmosis causes water to flow through cell walls to root interior where there is a lower concentration of water.
Passive Transport
Kinetic energy that moves molecules. Does not require energy, like in Osmosis or Diffusion.
Active Transport
To move from regions of low concentration to high concentrations, energy must be used. Movement against the concentration gradient requires energy. Also known as active transport.
