how does a slick tire give its grip compared to grooved or threaded tires???

Tires that are deliberately slick (rather than tires that are just worn out and slick) are made up of a very soft compound that becomes very, very sticky as it heats up. Actually, on dry roads, slicks have at least as much "stick" as do treaded tires. What treads in a tire do is channel water out to the sides of the tire and allow as much tread as possible to come in contact with the road for traction, whereas a slick will just hydroplane. There used to be an old joke on race tracks: "If it's raining, a VW Beetle can win a race on a NASCAR track because it will be the only car out there." Racing slicks get REAL slippery in the rain!

Slicks and drag radial tires are made up of a soft compound that allows them to become very sticky when heated. Since slicks dont have any tread the entire surface of the tire comes in contact with the ground. If you go to the track you can actually watch chunks of tire come flying off slicks when people do burn outs or take off to hard with a car that has to much hp. Its called "blowing the tires off your car" Slicks have much, much, much better traction then treaded tires on dry roads. You can shave as much as a half second or more off you 1/4 mile times just by running on slicks or drag radials.

A slick is softened by the pre run burn out and has more surface area contacting the pavement than a treaded tire

Because it does not have tread. The tread squirms and has gaps in the tire. The slick is just solid rubber all the way across the tire.

most slicks are made of a softer compound of rubber that helps them grip also due to having no tread they have more surface area on the pavement

but in water they have no where for the water to go so they hydroplane easily

it's the compound that the tire is made of