system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does wetting your hands make it easier to open a plastic bag, when having wet hands usually makes it difficult to handle other things?

Title pretty much says it.  I searched and couldn't find an answer. But having wet fingers seems counter intuitive, but makes opening trash bags and such way easier. How?
gpt
Your dry fingers have difficulty adhering to the smooth plastic. When you wet your finger, the water fills the spaces between your skin and the plastic bag. Water molecules are slightly bent, which means that they act a little bit like small magnets, with a small attractive force between them. This small attractive force (Van der Waals forces) causes the water to bond to both your fingers and to the bag, allowing you to grip it better. The forces in this case are small and the bag is light, so the force your hand apply is lower than the Van der Waals force.

When opening a jar, the Van der Waals force is still there, but you are applying a much larger force to try to open the jar. In this case, you grip the jar much harder, which increases the surface area contact and allows you to transmit the force from your hand to the jar and lid, hence opening it. When the jar and lid is wet, the water gets between your hand and the jar. Water is a fluid and cannot transmit shear force (the force of objects moving alongside one another), so your hand slips as soon as you apply a force greater than the Van Der Waals force.