What does "form a more perfect union" promise in the preamble

Elements and compounds are pure substances that cannot be broken down physically into a simpler substance. a physical change doesn’t break the bonds between atoms of a substance or form new ones. compounds can be broken down by a chemical change. a chemical change breaks chemical bonds and/or forms new ones between atoms of a substance. what simple substance would a compound break into? the basic elements that make it up! for example, if you passed a very strong electric current through water you’d break the chemical bonds in water and be left with oxygen and hydrogen. which of the following is an example of a chemical change? a separating water into different glasses b breaking frozen ice cubes with a hammer c running an electric current through water d boiling water to evaporate it on a stove

Why is it important to reduce the number of chromosomes in half when forming gametes for sexual reproduction?

When the cell concentrates potassium within, against the natural tendency of matter, it is performing a. passive diffusion b. facilitated diffusion c. active transport d. pinocytosis