Energy is needed to combat entropy. Matter is neither created nor destroyed during a chemical change. The mass of starting materials equals the mass of products. D. Theories are tentative, there are some facts to support them, but not enough to make a law. E. Models Pictures represent processes that are too small to see.
Models are testable, explanatory and tenative.
This DNA damage may lead to cancer. The amount of uncertainty in measuring data increases from math to biology to the social sciences. There is more variability in test tubes than with calculations on paper, more variability with cells than test tubes, more variability with rats than cells and more variability with humans than rats. Weight is a force. Force varies with gravity.