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Produced by the Chemistry Group, UCC, as part of DelPHE-funded collaboration between University of Cape Coast and The Open University, UK
Typology: Lab Reports
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A. Teacher’s Guide B. Students Guide C. Assessment – Student’s sheet D. Extensions to experiment E. Links to other packs F. Health and Safety G. Evaluation of pack
Curriculum areas covered:
Physical and chemical changes Compounds, mixtures, solute and solvents Homogenous and heterogeneous mixtures
Title: Distillation of rubbing alcohol (2-propanol) and water mixture
Target group: Teacher Trainees (DBE)
Also suitable for: SHS students
Duration :
Learning outcomes:
These are the learning outcomes expected after students have gone through this Pack.
KN1 define the term distillation KN2 list the types of distillation
CS1 demonstrate knowledge and understanding of the concept of distillation. CS2 to predict which of the solvents in the mixture would be distilled first.
KS1 identify that liquid-liquid mixtures can be separated
PS1 assemble the distillation set up for the separation purpose PS2 record observations based on the experiment
Purpose:
The experiment is to help with the separation of liquid-liquid mixture.
Background Information
Distillation is an extremely useful technique that is used to purify and separate liquid- liquid mixtures. There are three common types of distillation –simple, fractional and steam distillation.
Simple distillation is used to separate the components of a liquid- liquid mixture if the boiling points of the liquids are further apart. If the boiling points of the liquids are closer together then fractional distillation has to be used. Steam distillation is used to separate an immiscible mixture of essential oil and water. In each of the processes, the liquid mixture is placed in the distilling flask as shown in Figure 1. As the flask is heated, the lower boiling liquid vaporizes faster than the higher boiling liquid. Thus, although both components are in the vapor phase, the vapor is richer in the lower boiling liquid. The resulting vapor could be condensed and re-evaporated making the resulting vapor still richer in low boiling liquid. If the process is repeated a sufficient number of times, a separation of the two volatile components can be achieved
Figure 1. Distillation of rubbing alcohol and water mixture
Equipment/ Materials needed
Bunsen burner or source of heat 250 ml conical flask or round bottom flask – distilling flask Tripod stand Wire gauze Thermometer boiling chips Liebig condenser fitted with rubber tubings Water source 3 small receptacles (small beakers or conical flasks) Rubbing alcohol Distilled water
Other requirements
Practical notebook/ Writing material. Working bench/table, Open space, Laboratory coat, Eye goggles, Hand gloves
Experimental Procedure
Reflection on the experiment
In the distillation of crude oil, the different fractions are condensed out at different points in a huge fractionating column. Give examples of the distillate produced. What type of distillation is employed here?
Complete the table below by checking the properties of the solutions
Property butanol water
Odor Boiling point Dissolve in common salt Dissolve in naphtha
www.ncsu.edu/sciencejunction/depot/experiments/water/lessons/ph/index/html www.sciencepark.etacude.com/projects/php Orna, M. V., Schreck, J.O. and Heikkinen, H. Eds. (1998). Welcome to Reactions in Chemistry. ChemSource Version 2.1. New Rochelle, NY,
a. Do not eat, drink or chew whilst doing the experiment. b. Keep your face at a safe distance from open flames and heated solutions. Never look into a heated solution from above. c. Avoid breathing in dust or vapour. When smelling solutions, gently wave the air above the solution towards your nose with your hand. d. Wash any spilled solutions from your skin with plenty of water, and notify the instructor. e. Report any accident, no matter how minor, to the instructor/report the nearest health post.
Compulsory rules
You will not be allowed to do the experiment unless you are wearing the following items: a. Long-sleeved overcoat that is long enough to cover the hips, worn closed at all times. b. Safety glasses. Please note that contact lenses do not provide eye protection and in some cases may complicate an emergency (caustic liquids which splash into the eye can be
trapped behind the contact lens). You are advised to avoid wearing contact lenses in the laboratory, if possible. c. Closed, flat-heeled shoes (no open sandals). d. Long hair and loose scarves must be tucked away or tied up. e. If you are using toxic or corrosive chemicals you use protective gloves.
Tidy working Keep your working area tidy. A cluttered bench is a common contributory factor to accidents. Cleaning the glassware after use should be done immediately. This prevents the organic tarry material from attacking the surface of the glass. Always clean up a chemical spill without delay Clean up and dispose off your unknown substances according to your teacher’s instructions.
a. Was it difficult/easy to have access to the experimental materials listed? b. Were the experimental procedures easy to follow? Explain. c. Suggest other methods and materials which can be included in this pack.
