Why Do Heavier Particles Float in a Colloidal System?

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Heavier particles can float in a colloidal system due to interactions with lighter materials, such as styrofoam. In this case, silica particles, which are denser than the liquid (2M hydrobromic acid), bond with the styrofoam, creating a compound with a lower overall density. This results in the combined particles floating rather than sedimenting. The phenomenon highlights the importance of particle interactions and density changes in colloidal systems. Understanding these dynamics can clarify why heavier materials may not always settle as expected.
fifi olu
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Hi,

Sorry for double posting but I wasn't sure of the right thread.

I am working with a colloidal system in which the particles are heavier than liquid. However when I add styrofoam to the system, the particles float. I can't seem to understand why the heavier particles float instead of sediment. Please help.
Thank you.
 
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hi there
welcome to PF :)

you need to explain/clarify your experiment a bit more

what is the liquid ?
what is the denser material?
However when I add styrofoam to the system, the particles float <---- what do you mean by this ?

Dave
 
davenn said:
hi there
welcome to PF :)

you need to explain/clarify your experiment a bit more

what is the liquid ?
what is the denser material?
However when I add styrofoam to the system, the particles float <---- what do you mean by this ?

Dave
Hi Dave, thank you very much for your response.

the liquid is 2M hydrobromic acid (density: 1.49g/cm3)
the denser material is silica (density: 2.65g/cm3)
the sililca is dispersed in the acid. but when I add styrofoam balls to the mixture, the dispersion separates into 'acid at the bottom' and 'styrofoam with silica at the top'.

thank you again.

fifi
 
I guess you answered your own question: Styrofoam with silica

The silica must bond with the styrofoam, and the resulting compound particles have a smaller density than the acid. Note that in soft condensed matter the bond can be "soft", such as electrostatic, ...
 
https://www.physicsforums.com/threads/denser-material-floats.772393/reply?quote=4861154hank you very much M Quack. I thought as much; I just doubted myself.
 
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