Investigating Hydrogels - Chemistry Club

This week in Chemistry Club, students investigated the hydrogels which are present in items such as nappies and hair gel.   

Hydrogels are polymer chains (lots of atoms linked together) that are ‘hydrophilic’ - which means they love water! This makes them super absorbent. Disposable nappies contain a synthetic polymer (sodium polyacrylate) that can absorb a vast amount of water. Students extracted the hydrogel (approx. 15 ml) from the nappy core.   When distilled water was added, the hydrogel swelled up extremely quickly and became a very viscous mixture.  Students were surprised to see how much water (500 ml) was absorbed by the tiny crystals.

Hair gel is an example of a saturated hydrogel (which means it has already soaked up water) and this can be released by adding salt to the gel. Ions present in the salt displace the water molecules within the gel because they are more strongly attracted to the polymer than water. As soon as students added salt to the viscous hair gel, the hydrogel structure collapsed, and it turned into a runny liquid! 

 

Chemistry Club takes place every Thursday in S4 from 1.25pm.  It is open to all students in Years 9,10 and 11. 

Mrs Arain, Science