chem test

Some mixtures look like they are pure substances. For example, a mixture of salt dissolved in water looks the same as pure water. Air is a mixture of several gases, but you cannot see the gases that make up air. mixture homogeneous heterogeneous Heterogeneous Mixtures A heterogeneous mixture does not have a fixed composition. Mixtures that are not uniform throughout are said to be heterogeneous. Not completely mixed For example, in a mixture of clay and water, heavier clay particles concentrate near the bottom of the container. Another naturally occurring heterogeneous mixture is granite, a type of igneous rock. Granite is a mixture of crystals of the minerals quartz, mica, and feldspar. Particles in a suspension are large and settle out. Natural orange juice is a suspension of orange pulp in a clear liquid that is mostly water. Suspension is a mixture in which particles of a material are more or less evenly dispersed throughout a liquid or gas. When the orange juice carton is not shaken, the top layer of the juice in the carton is mostly water because all of the pulp has settled to the bottom. You can see that orange juice is a heterogeneous mixture. Particles in a suspension may be filtered out. Particles in suspensions are usually about the size of a bacterial cell, which has a diameter of about 1,000 nm. Particles of this size are large enough to be filtered out of the mixture. For example, you can use a filter made of porous paper to catch the suspended pulp in orange juice. That is, the pulp stays in the filter, and smaller particles, such as water molecules, pass through the filter easily. You can classify a mixture as a suspension if the particles settle out or can be filtered out. Some mixtures of two liquids will separate. Oil, vinegar, and flavorings can be shaken together to make salad dressing. But the dressing is a heterogeneous mixture. When the dressing stands for a few minutes, two layers form. The two liquids separate because they are immiscible, which means that they do not mix. Eventually, the oil, which is less dense, rises and floats on the vinegar, which is denser. miscible: substances that can be mixed.  immiscible: substances that cannot be  mixed. One way to separate two immiscible liquids is to carefully pour the less dense liquid off the top. The process of pouring a less dense liquid off a denser liquid is called decanting. Particles in a colloid are too small to settle out. Colloid a mixture consisting of tiny particles that are intermediate in size between those in solutions and those in suspensions and that are suspended in a liquid, solid, or gas Latex paint is an example of another kind of heterogeneous mixture, a colloid. The color in latex paint comes from solid particles of colored pigments that are dispersed in water. The difference between colloids and suspensions is that the particles in colloids are smaller than those in suspensions. Particles in colloids range from only 1 to 1,000 nm in diameter. Because the particles in colloids are so small, they pass through most filters and stay spread throughout the mixture. Even though the colloid may look like clear water, the particles are large enough to scatter light that passes through the colloid. This scattering of light is called the Tyndall effect. Other familiar materials are also colloids. Gelatin, egg whites, and blood plasma are all protein colloids. They consist of protein molecules dispersed in a liquid. Whipped cream is a colloid that is made by dispersing a gas in a liquid, and marshmallows are made by dispersing a gas in a solid. Fog is made of small droplets of water spread in air, and smoke contains small solid particles dispersed in air. Some immiscible liquids can form colloids. Mayonnaise is a colloid made up of tiny droplets of oil suspended in vinegar. Vinegar-and-oil salad dressings separate into two layers, but the egg yolk in mayonnaise keeps the oil and vinegar from separating. Egg yolk coats the oil droplets so that they do not join together and form a separate layer. Mayonnaise is an emulsion, a colloid in which liquids that usually do not mix are spread throughout each other. Emulsions are also found in your body. In the small intestine, bile salts cause fats to form an emulsion. Then, enzymes can break down the smaller fat particles more quickly. Emulsions are a type of colloid with very small particles that make them appear uniform but are not. Example of Emulsion - Cream: Cream appears uniform but is a mixture of oily fats, proteins, carbohydrates, and water. Lipid droplets in cream are coated with proteins that act as emulsifiers, preventing separation. The protein coating keeps lipid droplets dispersed in water, allowing them to stay spread throughout the mixture. Emulsification helps in maintaining a stable mixture and facilitates biological processes like fat digestion. Emulsion is any mixture of two or more immiscible liquids in which one liquid is dispersed in the other. Homogeneous Mixtures A homogeneous mixture looks uniform even when you examine it under a microscope because the individual components of the mixture are too small to be seen. Homogeneous mixtures, such as salt water, are uniform. Salt and water do not react when mixed. So, the two substances can be separated by evaporating the water. Homogeneous mixtures are solutions. Homogeneous mixtures have the smallest particles of one substance uniformly spread among another. Solution is a homogeneous mixture throughout which two or more substances are uniformly dispersed. All homogeneous mixtures are also solutions. Components of a Solution: Solute: The substance that dissolves (e.g., salt or sodium chloride). Solvent: The substance in which the solute dissolves (e.g., water). When a solute dissolves in a solvent, the solute separates into the smallest particles of the substance—atoms, ions, or molecules. Miscible liquids mix to form solutions. Miscible liquids mix to form a single layer without separating. Example: Water and isopropanol (rubbing alcohol). Unlike immiscible liquids, miscible liquids do not form layers, making separation more challenging. Distillation is a common method to separate miscible liquids. Separation relies on differences in boiling points of the liquids. Example: A mixture of methanol and water can be separated because methanol boils at 64.5°C, while water boils at 100.0°C. When heated, methanol boils and evaporates first, leaving most of the water behind. Liquid solutions sometimes contain no water. Some solutions are liquids mixed in other liquids without containing water. Examples: Fingernail-polish removers and paint strippers. Fuels like gasoline, diesel, and kerosene are homogeneous mixtures of various liquid carbon compounds. These fuels are derived from distilled petroleum. Some hydrocarbons obtained during the distillation of petroleum are used to make plastics. Other states of matter can also form solutions. Solutions can involve solutes and solvents in any state: solid, liquid, or gas. Solids in liquids: Salt dissolved in water. Liquids in liquids: Vinegar (acetic acid dissolved in water). Gases in gases: Air (a mixture of nitrogen, oxygen, argon, etc.). Gases in liquids: Soft drinks (carbon dioxide dissolved in water). Liquids in solids: Amalgam (mercury dissolved in silver, used in dental fillings). Solvent: The substance present in the largest amount. Solute: The substance present in the smaller amount. Solids can dissolve in other solids. Brass is an alloy made by dissolving zinc metal in copper metal. Metals are melted into liquids, mixed, and then allowed to cool. Upon cooling, a solid solution of one metal dispersed in another forms. Alloys like brass are widely used in manufacturing musical instruments and other objects due to their unique properties like strength, durability, and resistance to corrosion. HOMEWORK