Glue

Hit it, boys!
I can show you two main ways that glue works
The first is called mechanical locking
Mechanical locking uhn?
How does that work?
Just listen

When you use a gob of glue
Just what exactly does it do to get things sticking?
It can fix a flower pot or any broken toy you've got
But how? (Uh oh!)
If you magnify the smoothest stuff, it's coarse and rough, you'll see
Cracks and dents are many, yes, there are plenty
Here and there, everywhere roughness is the key
Glue goes into tiny cracks, it oozes into all the gaps
And there it hardens (Oh!)

Everywhere that it can drip
It gets a firm and hearty grip
And so, when it dries completely then its grip is good and strong
There you go, good as new
Through and through 'cause the glue won't let go
(That's mechanical locking, but glue also works on a molecular level)

Atoms make up everything, that's the rule
Though they're tiny, not very large
And they combine into clusters called molecules
Which often can have an electric charge
Those have a couple of different ends, positive and negative too
And when opposing ends line up, they stick to each other
Like pairs of magnets do (it's true!)
(There's a name for that, Van Der Waals forces)

Now the molecules of glue are clinging by the millions
To the things you're joining
So it helps them stick together
That's the coolest thing I've ever seen

Glue can work in many ways, I've shown you only two
But when you build a model truck or fix a handle on a cup
Just think of all the great things glue can do!