Chemical reactions that energy often occur spontaneously

Chemical reactions that release energy often occur spontaneously. Chemical reactions that absorb energy will not occur without a source of energy. An example of an energy-releasing reaction is hydrogen gas burning, or reacting, with oxygen to produce water vapor. direction the reaction requires energy.

Explanation:

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the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands

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