During an exothermic chemical reaction,
a. a system becomes warmer, and the chemical substances undergo a decrease in potential energy.
b. a system becomes warmer, and the chemical substances undergo an increase in potential energy.
c. a system becomes cooler, and the chemical substances undergo a decrease in potential energy.
d. a system becomes cooler, and the chemical substances undergo an increase in potential energy.
e. a system becomes warmer, and additional heat is gained from the surroundings.

B.

Explanation:

When an exothermic chemical reaction occurs the substance becomes warmer and it gains potential energy

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ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.