Matter is anything that has mass and takes up space. Elements are one element that cannot be broken down further while compounds are more than one element. Hetero is multiple while homo is one.

Acids are toxic along with bases. 7 is neutral which is in between bases and water.  An acid is stomach acid and a base is drain cleaner and I know stomach acid is an acid because it can dissolve any food and I know drain cleaner is a base because we read about it previously.