Mixtures

Objectives Know the types of mixtures and how they are found in the environment. Be able to identify the type of mixture. Understand the terms colloid, suspension, solution, concentration gradient, and alloy. Predict how osmosis and diffusion will cause particles to move.

Mixture Matter that consists of two or more substances mixed together but not chemically combined is called a mixture. Some mixtures may look similar but may have different properties. Stainless steel is a mixture of chromium and iron. + =

Types of Mixtures There are two major types of mixtures: Heterogeneous Mixture Homogeneous Mixture

Heterogeneous Mixture A mixture that does not appear to be the same throughout. Ex. Salads Parts of a heterogeneous mixture can be easily separated. Ex. Sand and water

Types of Heterogeneous Mixtures Suspension – A mixture that looks uniform when stirred but separates into different layers when not agitated. Ex. Orange Juice, Blood. 2. Colloid – A mixture of small particles in a liquid that do not settle out. Ex. Milk.

Homogeneous Mixtures A mixture that appears to be the same throughout. Ex. Toothpaste, whipped cream, stainless steel.

Solutions are Homogeneous Mixtures!!! A Solution is a type of homogeneous mixture of two or more substances in a single phase. These are almost always liquids. Examples include ocean water, lemonade, or alcohol. A solution always has a substance that is dissolved and a substance that does the dissolving.

Parts of a Solution Solute – The substance (usually a solid) that is dissolved. Solvent – The substance (usually a liquid and almost always water) that does the dissolving. Solubility – The ability of a substance to dissolve another substance. This is a function of temperature.

Alloy A Homogeneous mixture of two or more metals Stainless Steel = Steel + Chromium Steel = Iron + Carbon

How Do Substances Move? CONCENTRATION GRADIENT - the number of molecules or ions in one region is different than the number in another region In the absence of other forces, a substance will naturally move from a region where it is more concentrated to one where it is less concentrated A substance naturally moves “down a concentration gradient”

Membrane Crossing Mechanisms DIFFUSION OSMOSIS

Diffusion EQUILIBRIUM Movement from an area of high concentration to an area of low concentration. Only the kinetic energy of the molecules is necessary; no additional energy is required. A form of PASSIVE TRANSPORT that does not require energy Diffusion will occur until there is equal amounts of solute spread throughout the system: EQUILIBRIUM

Factors Affecting the Rate of Diffusion Steepness of concentration gradient Steeper gradient = faster diffusion Molecular size Smaller molecules = faster diffusion Temperature Higher temperature = faster diffusion Electrical or pressure gradients increase the rate of diffusion

Osmosis The movement of water across a selectively permeable membrane Membrane prevents solutes from moving across membrane with water. Water moves to equalize concentration inside and outside of cell. Water solution Glucose solution

Diffusion

Terms ISOTONIC HYPERTONIC HYPOTONIC Equal: concentration of solutes is equal inside and outside the cell. No net movement of water HYPERTONIC Higher solute concentration outside the cell than inside of the cell. Net movement of water is outside of the cell. HYPOTONIC Higher solute concentration inside the cell than outside the cell. Net movement of water is into the cell.

1 liter of distilled water 2% sucrose solution 1 liter of distilled water 1 liter of 10% sucrose solution 1 liter of 2% sucrose solution a b c Hypotonic Solution Hypertonic Solution Isotonic Solution