Chem Lab

Topics: Solution, Mixture, Chemical substance Pages: 4 (840 words) Published: January 31, 2011
Types of Mixtures Lab

Purpose
• To classify types of mixtures
• To determine the polarity of substances

Background Information: Polarity
In the middle of the night of March 24, 1989, the giant oil tanker Exxon Valdez veered out of the shipping lanes in Alaska’s Prince William Sound and struck a reef. The side of the tanker was ripped open, and 11 million gallons of crude oil flowed out into Alaska’s clear blue waters. Because petroleum oil is insoluble (does not dissolve) in water and less dense, it quickly spread across the surface. The oil slick eventually covered 10,000 square miles, contaminating 1500 miles of shoreline, and causing substantial damage to wildlife, the fishing industry, and the marine environment.

Chemists say “like dissolves like,” meaning that polar solvents tend to dissolve polar solutes, and nonpolar solvents tend to dissolve nonpolar solutes, while nonpolar and polar substances are immiscible (do not mix). Because petroleum is nonpolar and water is polar, the oil from the leaking Exxon Valdez did not mix with the seawater, but rather spread across its surface.

Pre-lab Questions
(1) What is the difference between a heterogeneous mixture and a homogeneous mixture? (2) Compare and contrast the properties of solutions, colloids, and suspensions. (3) What is the difference between the “solute” and the “solvent?” (4) How does a “phase” of matter differ from a “state” of matter? (5) Explain the rule like dissolves like. Use the terms “miscible,” “immiscible,” “polar,” and “nonpolar” in your answer.

Materials
7 cupsGraduated cylinderSpoon
BeakerMilkStarch
DropperOilSucrose
FlashlightSaltTest tubes and holder
Food coloringSandWater

Procedure
(1) Prepare mixtures in different cups with about 200 mL of water and the following substances: (a) 3 teaspoons of sucrose (b) 1 teaspoon of starch (c) 1.5 teaspoons of sand (d) 5 drops of food coloring (e) 20 mL of oil (f) 0.5 teaspoons...
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