Solutions and Other Mixtures Chapter 7.1 Solutions and Other Mixtures

Objectives Distinguish between heterogeneous mixtures and homogeneous mixtures. Compare the properties of suspensions, colloids, and solutions. Give examples of solutions that contain solids or gases.

Heterogeneous Mixtures Heterogeneous mixtures do not mix thoroughly and do not look the same throughout. Heterogeneous mixtures include: Suspensions – a mixture that has large particles that will settle to the bottom after a period of time. Colloids – a mixture that has tiny particles spread throughout the liquid, solid, or gas.

Suspensions The particles in a suspension are large and will eventually settle to the bottom. Suspensions can often be identified by the presence of a “shake well before using” label. The particles in a suspension can be filtered out due to their large particle size. Sometimes, immiscible liquids will separate into layers. This allows the less dense liquid to be poured off the top in a method called decanting.

Colloids Particles found in a colloid are too small to settle to the bottom. Particles of a colloid are too small to filter. Even though the particles of a colloid are small, they still scatter light. This scattering of light is called the Tyndall effect. Emulsions – are specific types of colloids in which two or more immiscible liquids are dispersed throughout each other.

Homogeneous Mixtures Homogeneous mixtures look the same throughout because they are the same throughout. Homogeneous mixtures are solutions. A solution is a mixture of two or more substances that are uniformly dispersed throughout a single phase. Solute – the substance that dissolves Solvent – the dissolving agent (Water is universal solvent.)

Solutions The particles of a solution are atoms, ions, or molecules and are extremely small. These particles are so small that they do not scatter light, meaning they do not demonstrate the Tyndall effect; this distinguishes between solutions and colloids. Solutions may be formed from solids, liquids, or gases. Miscible liquids mix to form solutions. Miscible liquids are simply liquids that mix together. Miscible liquids cannot be decanted and are usually separated using distillation.

Solutions Liquid solutions do not have to contain water. Examples: gasoline, diesel, kerosene, paint strippers, etc. The air we breathe is a solution of gases. Nitrogen, oxygen, argon, carbon dioxide make up the air we breathe. Gases can also be dissolved in liquids, such as in soft drinks. Alloys are solutions containing different metals (solids.) Alloys are important because they have unique properties that the individual metals do not have.