How do you make a model of something you cannot see?

This is a characteristic of the elements in the periodic table that shows a pattern. it may increase or decrease across or down the table.

List four observations that indicate that a chemical reaction may be taking place

An animal cell loses the ability to convert energy stored in food to energy that the cell can use. which of the cell's organelles has stopped working? a.the mitochondria b.the nucleus c.the vacuoles d.the endoplasmic reticulum