My friends and I volunteer at a local library, teaching elementary students interested in science experiments. We visit this place once a week and help kids perform interesting tests and teach them how certain results occur.
Last week, kids and my team made a jelly-like substance, and the purpose of this experiment was to teach them about colloid.
Colloid is a substance at the phase in between liquid and solid state. Solid has a fixed structure of molecular binding, and liquid has a rather loose structure, so colloid has a structure similar to those of both states.
- polyethylene glycol (oxide)
- a cup of water
- a stick for stirring
- a pipette
- a spoon
- plastic cups
- Have polyethylene glycol (oxide) prepared in a cup.
- Using a pipette, pour 14mL of ethanol and stir using a stick to make sure two substances are perfectly mixed together.
- Prepare another cup, and mix 50mL of water and pigment.
- Pour the mixture of 3 into the mixture of 2.
- Colloid is created!
Polyethylene oxide(PEO) is a polymer composed of many ethylene oxides(EO). PEO has high affinity for water, so when it meets water, they bond very easily. Ethanol helps water and PEO bond more easily.
One thing about PEO is that when it meets water, it gets really sticky. That is why when we added water to the mixture of PEO and ethanol (process 4), the resulting substance got really sticky and turned into a colloid!
Colloid is being used in many different fields. To name one example, soothing ointments that people use when they are hurt are all created using colloids!