Name: _______________________ Date: ________________________ Flynt - ___Period ___th Grade Science A solution is a mixture of one substance dissolved in another so the properties are the same throughout. A solution is composed of a solute and the solvent. The solute is the substance being dissolved and the solvent is the part of the solution that does the dissolving. The solute is of molecular size. Examples of Solutions: Gas Liquid Solid Gas Oxygen and other gases in nitrogen (air) Liquid Carbon dioxide in water (carbonated water) Ethanol (common alcohol) in water; various hydrocarbons in each other (petroleum) * Sucrose (table sugar) in water; sodium chloride (table salt) in water Solid Hydrogen dissolved to palladium Water in activated charcoal Steel, Brass, other metal alloys Water vapor in air (humidity) The odor of a solid -molecules of that solid being dissolved in the air * Two liquids that are soluble are said to be miscible in one another. Strength of Solutions The solubility is the amount of solute that be dissolved in a given amount of solvent at any one temperature. A solution is said to be unsaturated as long as more solute can be dissolved. Dilute or Weak Solution - only a small amount of solute compared to solvent. Concentrated Solution - A relatively large amount of solute to solvent. Saturated Solution --At this point, the concentration of the solute in solution is the maximum possible under the existing conditions (temperature and pressure). A solution is saturated when no more solute can be dissolved at the current temperature. A saturated solution is one in which the dissolved and undissolved solutes are in equilibrium. Supersaturated Solution -- a solution that contains more dissolved substance than does a saturated solution; the solution is not in equilibrium with the pure substance. An example of a supersaturated solution is carbonated water, which is a supersaturated solution of carbon dioxide gas in water. At the elevated pressure inside a Coca-Cola bottle, more carbon dioxide can dissolve in water than would dissolve at atmospheric pressure. If exposed to atmospheric pressure, the carbon dioxide gas would escape very slowly from the supersaturated liquid; this is why your Coke goes flat over time. However, the escape process may be accelerated by the presence of nucleation sites within the solution, such as small bubbles, which may be caused by shaking the bottle, or adding another solute, such as sugar powder. A Diet Coke and Mentos eruption is a rather extreme example. Other examples: Super-saturated solutions of sugar and water are commonly used to make rock candy. Scuba divers' tissues become saturated with breathing gases during a dive. If the diver ascends too fast, these gases form bubbles, resulting in decompression sickness. Water is the Universal Solvent Although water is sometimes called the universal solvent, there are many things it cannot dissolve. For example water and oil do not mix. We say oil is immiscible in water. What makes water such a good solvent? Water is a good solvent due to its polarity. The solvent properties of water are vital in biology, because many biochemical reactions take place only within aqueous solutions When an ionic or polar compound enters water, it is surrounded by water molecules. The relatively small size of water molecules typically allows many water molecules to surround one molecule of solute. The partially negative dipoles of the water are attracted to positively charged components of the solute, and vice versa for the positive dipoles. Assessment Questions: Multiple Choice Questions 1. In a solution the substance that does the dissolving is called ___ a) soluble b) the solute c) the solvent d) an ion 2. Water is a good solvent because a) Water is a good solvent because it is a negatively charged ion. b) Water is such a good solvent because it repels most molecules c) Water is such a good solvent because it is such a small molecule d) Water is a good solvent due to its polarity and small molecular size 3. A solution that cannot hold any more solute at room temperature would be ___ a) a dilute solution b) a concentrated solution c) a saturated solution d) a supersaturated solution 4. Ethanol dissolved in water would be an example of ___ a) a solution between two miscible liquids b) a solution between a solid and liquid c) a suspension between two liquids d) ethanol and water do not form a solution 5. To form a supersaturated solution requires a) reducing the amount of solute b) increasing the amount of solute in a solution c) increasing the temperature of a saturated solution so more solute can be added d) none of the above