Exploring Colors in Chemistry Labs

SIFC Chemistry Teacher: Dr. Brian Li

Chemistry courses in SIFC are designed to train students’ practical skills through series of laboratory experiments. Throughout the whole school year, students will also gain many other experiences along with academic ones. For example, during the first four weeks, students have explored different ways to separate matters from their mixtures. 

Method 1: Filtration plus evaporation

Students were given a ‘simple’ task to extract sugar from some insoluble solids. Simple action requires decent skills as you gently boils sugary water. Mistakes could be made because you are not patient enough or not precisely control the speed of heating. Unluckily, you failed in the first trial, but you luckily observed GOLDEN colored syrup emerged in the beaker.

Method 2: Distillation plus condensation

Students were tasked to purify 70% drugstore ethanol. Plain simple principle is stated, but complex set-up is required. An interesting thing is that ethanol is colorless so that its appearance won't tell you 80% or 90% of it. Only its density tells you at end. So don't fool yourself by its color.

Method 3: Recrystallization plus nucleation

Students were to set for purer copper sulfate crystals. It’s a fabulous process which you could fully enjoy as you are making fantastic blue colored CRYSTALS! But careless you were, forget to stir solution to stop nucleation. All little ‘baby’ crystals would stick together at the bottom of your beaker. It’s not a joke that they are hard to be poured out.

Method 4: Solvent extraction

Students were inspired to extract iodine from tincture iodine. Oohing! It is that iodine belonging to the family of halogens, which is black colored in solid subliming into PURPLE gas. After shaking the tube up and down, a trace of iodine elegantly moved up into the clear phase.

Method 5: Paper chromatography

Is BLACK just black, BLUE just blue? Students were settled in performing an impossible ‘mission’ to find other colors in back/blue. Eventually they were amazed by the spectrum presented on the filtering paper strips. As different strengths of interactions with paper and solvent, all hidden pigments of different colors were separated.

Throughout the series of experiments, students not only gained hands-on skills in laboratory but also get appreciation for such colorful applications of Chemistry in our daily life.