When two or more substances are mixed together, what you get is called a mixture.

In a mixture, each material is still itself.

To find out whether mixing made a new substance, look for the four signs.

In the quiet cup, the baking soda spread through the water.

There are no bubbles, no new color, no new solid, and no warming or cooling.

The quiet cup after stirring: clear water, no bubbles, no flakes, not warmer or colder.

Did mixing make a new substance? No, it did not: no sign appeared.

The baking soda is still itself, so the quiet cup holds just a mixture.

In the fizzing cup, bubbles rushed up, and the cup got colder by itself.

The fizzing cup: bubbles rush up, and the cup feels colder.

Did mixing make a new substance? Yes, it did: two signs appeared.