Asphalt is a thick, sticky, black or dark brown substance used to pave roads, parking lots, and driveways. It's made by mixing crushed rock and sand with a petroleum product called bitumen, which acts like a strong glue holding everything together. When workers lay fresh asphalt, it's hot and soft enough to spread smoothly, but as it cools, it hardens into the durable surface you walk, bike, and drive on every day.

Almost every road you've traveled on is probably paved with asphalt. Road crews pour and roll it flat, creating that smooth black surface that can handle thousands of cars driving over it. On a hot summer day, you might notice asphalt feels warm or even soft under your feet because it absorbs heat from the sun.

Asphalt is also called blacktop because of its dark color. People sometimes confuse asphalt with tar, but they're different materials. Asphalt comes from petroleum, while tar comes from coal. Cities prefer asphalt for roads because it's relatively inexpensive, can be repaired easily, and provides good traction for tires, even when wet.