When you swallow food why does it not usually enter the respiratory system?

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

How do you date a sample of rock that you suspect as being one of the earliest on earth

Both destructive and constructive, the natural event seen here, is important in destroying and creating landforms on earth. what is this event called? a) deposition b) flooding c) landslide d) sedimentation