C8 - Chemical Analysis

• pure substance is something that only contains one compound or element
• a chemically pure substance will melt or boil at a specific temperature. you can test the purity of a sample by measuring it is melting or boiling point and comparing it with the melting or boiling point of the pure substance. the closer your measured value is to the actual melting and boiling point the purer your sample is
• formulations are useful mixtures with a precise purpose
• mobile phase : molecules are moving
• stationary phase : molecules can not move
• chromatography : draw a pencil line 1 cm from the bottom of the filter paper. add several dots of die on the line. next dip and hold paper in in the solvent and watch the dye travel up the paper. the dyes with the higher solubility will travel further up the paper
• the amount of time the molecule spend in the mobile and stationary phase depends on how soluble there are in the solvent and how attracted they are to the paper
• Rf value is the ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent
• Rf = distance travelled by substance / distance travelled by solvent
• chlorine bleaches damp litmus paper turning it white
• oxygen : if you put a glowing splint inside a test tube containing oxygen the oxygen will relight the glowing splint
• carbon dioxide : bubbling carbon dioxide through an aqueous solution of limewater causes the solution to turn cloudy
• hydrogen : if you hold a lit splint at the end of a test tube containing hydrogen you will get a squeak pop