I am teaching my 8th grade students that the two factors determining the amount of friction is the type of surface and amount of force applied on the two surfaces. I am reading on the Internet that it is not surface that determines the amount of sliding friction, but a chemical bonding between the two. Is this true?

Yes, but in general rough surfaces do have higher sliding friction. I'm not sure if the accuracy/confusion trade off is worth it with 8th graders.

Yeah... different surfaces have different coefficients of friction... which ties into a mathmatical formula...

I used to work for an ink manufacturer whod sell ink that was printed on all kinds of plastics mostly... well, the people who made goods like insulation wanted a package that didn't have a lot of slip... meaning the friction between the two packages was higher... meaning that they could be stacked higher and wouldn't slide... wed formulate the ink to have a higher coefficient of friction. This was done by the omission and addition of certain additives to the ink. The ink then not only told the customer about the product, but also had a functional purpose for safety and display issues.

So yeah, some things experience less friction... think about all the technology that goes into the swimsuits of olympic swimmers or racers... they want less drag through the air or water...

I wouldn't get too much into chemical bonding unless they've already seen some of this...