Lab04-Element, Compounds & Mix. 5-02EJM

Lab04-Element, Compounds & Mix. 5-02EJM -...

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Name____Erica Murray__ By Dr. Adams (5-03edit.) Elements are the basic building blocks of nature. At the time of this writing, scientists have detected 115 different elements. The smallest unit of an element is an atom . An atom of an element has the properties of that element. Elements can combine chemically to form new substances called compounds. A compound is a pure substance with a unique set of chemical properties. A compound is represented by a chemical formula. A chemical formula of a compound is usually the smallest unit of the compound that would have the properties of that compound. The formula lists the types and numbers of atoms in that compound. In this laboratory exercise you are to examine a sample that is a mixture of two compounds. One compound is water-soluble (dissolves in water) and the other compound is water-insoluble (does not dissolve in water). You will be using physical processes to separate the two components. After separating the two components, the weight percentage (%) of each component will be calculated. Silver nitrate (AgNO 3 ) will be used in this exercise to test for the presence of substances in water solutions. Solutions made with water are also called aqueous solutions . Silver nitrate is very reactive with most elements and compounds. Silver nitrate is soluble in water, but does not react chemically with water. When silver nitrate is added to pure water, normally no change is seen in the appearance of the water solution. The appearance of distilled water with added silver nitrate solution is a control used for comparison in this laboratory exercise. If silver nitrate is added to an impure water sample, changes are normally seen in the water sample. Such changes may include; the formation of a cloudy solution, the formation of a solid, or color changes that do not resemble the color of silver nitrate added to pure water. The reaction of silver nitrate when added to a water-based sample is a sign that something other than pure water is in the water sample. This test tells us little about the identity of any foreign substance in water, but is an easy test that may detect a foreign substance in a sample of water. We will use this test in this lab to test water samples for the presence of foreign matter. PROCEDURE A : Locate the baggie that contains your unknown mixture . Also locate your plastic funnel, filter paper, two 250 mL beakers, two 50 mL beakers, blue or white test tube rack, 4 open mouth test tubes, metal spatula and glass-stirring rod. You will need a gallon of distilled water for this course. If you have not obtained the distilled water, you will need to do so before you can adequately start this laboratory exercise. You can purchase distilled water in most large grocery stores. It should say “distilled water” or “steam distilled water” on the label. Do not purchase “drinking water” for this purpose unless it is labeled “distilled water” or “steam distilled water”. Weigh an empty dry 250 mL beaker (this beaker will be referred to as beaker #1) and record its weight in
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Lab04-Element, Compounds & Mix. 5-02EJM -...

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