IGCSE Coordinated Science Y1 Topic: Methods of Separation & Purification Monday, August 27 th Lesson 2

IN: Chromatography Lab Let’s revisit today’s lab… –Do Visa-Vis™, Monami, and Staedtler™ have a case against Crayola™? –Use observational “data” from your experiment to support your conclusion. Appropriate data means detailed observations or drawings/sketches of your chromatograms. Tape your chromatograms into your journal.

THROUGH:

Chromatography Wrap Up Answer the questions on the Chromatography Practice Sheet. We’ll discuss them in a few minutes!

Separation & Purification Techniques Review Crystallization-The formation of a solid from a solution, melted solid, or a vapor. –Example: Dissolving sugar in water then heating to evaporate the water and leave behind sugar crystals. Chromatography-A technique for separating the components of a mixture on the basis of differences in their attraction to a stationary and a mobile phase. –Example: Separating pigments that make up a dye.

Distillation-the process of purifying a liquid first by evaporation and then recollecting it through condensation –Example: Desalination of sea water Fractional Distillation-A special type of distillation where a mixture is separated into its component parts by using differences in their boiling point. –Example: Distillation of Crude Oil –Video Clip –Read more about crude oil purification on Pages in your Chemistry book and fill in the chart on the Help Sheet.

Fractional Distillation of Crude Oil Crude oil when it is mined is thick and sticky (not very useful). The oil is heated in the fractionating column which is hotter at the bottom and cooler at the top. The components with the lowest boiling point turn into vapor first. –Small hydrocarbons (chains of carbon and hydrogen) boil off first and are condensed and collected OR collected as a vapor. –Larger hydrocarbons require higher temperatures and are collected nearer to the bottom of the column.

OUT: How can scientists assess the purity of a substance? –Go to the Haiku page and use the links in the resource section of C1/C2 to answer this question. Why is it important for the food and drugs (i.e. medicines) to be pure?

Homework You will have your first TEST on Wednesday, August 29 th ! To prepare- Complete the C1/C2 Revision Guide at the back of your packet by Wednesday. Review your topic checklists and study your notes/packet.

EXTENSION You have been hired as part of a team of scientists to help solve a very important problem. In many countries there is little or no access to clean drinking water. Use what you know about separation and purification to devise a way to purify unsafe water using everyday objects.