What must happen before a chemical reaction can begin? The activation energy must be exceeded. The activation energy must be reached. The concentrations of products and reactants must be equal. The concentration of reactant molecules must be reduced.

The activation energy must be REACHED before a chemical reaction can begin.

A chemical reaction can be defined as a process where one or more substances called reactants, are converted to one or more products of that reaction.

The activation energy is the minimum amount of energy required to carry out a chemical reaction.

The higher the activation energy of a given chemical reaction, the slower this reaction will be.

An enzyme is a biological catalyst that helps to perform a chemical reaction by lowering its activation energy.

In conclusion, the activation energy must be REACHED before a chemical reaction can begin.

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Explanation:

For any enthalpy change in a chemical reaction, (exothermic/endothermic), the activation energy must be reached so as to break the strong chemical bonds between the reactant molecules.

answer: angiosperms

dicots

angiosperms are highly evolved plants, they produce seeds which are enclosed within in a carple. these are the largest group of plants on earth. they include trees, shrubs, herbs and small flowering plants. angiosperms exhibit a flowering stage in their life cycle. the flower serves the function of reproduction and fruit formation in majority of angiosperms. dicot is the term used to describe flowering plants that have two seed leaves. dicots are plants which develop seeds which split into two parts called cotyledons. each cotyledon contains one embryo.

here, a small purple flower development indicates that the plant belongs to angiosperms and having two embryonic leaves indicates it belongs to dicots.  

evidence and logical support is essential for a scientist to do in order to maintain credibility. this is because no one can believe without any logic and without any evidence.hence a scientist can maintain credibility by proving himself and by answering logically so experiments prove very beneficial. logical hypothesis give conclusion which is acceptable. therefore, there are two main factors to maintain credibility by a scientist is evidence and logical support.