Answer:
C. naturally uncombined with other elements.
Explanation: Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air.
Chemical reactions are at the essence of just about every biological and physical process in the whole universe. Stars form due to chemical reactions, our sun flamed up also because of chemical reactions in its core. Life basically evolved on Earth as an outcome of chemical reactions. The "circle of life" is, at its quintessence, a sequence of chemical reactions. Also our capacity to move and think is an outcome of chemical reactions that happen inside our bodies. Chemical reactions are the reason why new forms of matter are created. Chemical reactions make us comprehend the properties of matter. Chemical reactions make food into fuel for our bodies, they make fireworks blow up, they change food when it is cooked, they make soap remove dirt, and a lot more. Chemical reactions contribute to solving crimes and unravel mysteries. We can even find out which planets and moons are most likely to be able to preserve life. The most significant and momentous discovery made by humans, fire, is just a chemical reaction. Nothing would ever change without chemical reactions
Answer:
solution:-a homogenous mixture of two or more substances in relative amounts that can be varied continuously up to what is called the limit of solubility.
solute:-is a substance, usually a solid, that is dissolved in a solution, which is usually a liquid.
solvent:-substance, ordinarily a liquid, in which other materials dissolve to form a solution.
polar molecule:-is a molecule in which one end of the molecule is slightly positive, while the other end is slightly negative.
Nonpolar molecules occur when electrons are shared equal between atoms of a diatomic molecule or when polar bonds in a larger molecule cancel each other out.
concentration refers to the amount of a substance in a defined space.
Explanation:
The enthalpy change is negative.
The other statements are false because:
Can take place without a catalyst
Energy is given out to the surroundings.
Kinetic energy of products is higher.
