Choose all the answers that apply. Observations
can always be repeated
are usually quantitative
are made using the senses
are usually the start of the scientific method
can be misinterpreted

B,C,D,E

Explanation: They are usually conducted using measurements, an observation is made using your senses, they are usually the start, they can be misinterpreted because your senses can deceive you.

the answer is a! (2.9 x 10^-18 j) hope i could someone. : )

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.