Fill in the blanks with the word that best completes each statement. Scientists develop knowledge by making -about the natural world that may lead to a scientific question. A scientific question may lead to a(n) -which can be tested. The results of -can lead to changes in scientific knowledge.

1. observations

2. hypothesis

3. experimentation

Explanation:

Observations are made, Hypothesies are formed from observations, and experimnets help alter and comfirm hypothesis.

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.

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.