Which contribution from international organizations to fight disease is most necessary?

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

Look at the following answer choices and determine which belongs in the both category. testable, can be disproven explains natural phenomena, has evidence to support it prediction, tentative, one or more scientists working together well established, many different scientists working independently, highly reliable

What element is able to combine with itself and hydrogen to form large molecules ?