Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Q: Question: The total number of protons and neutorns in an atom is called what? Answer: mass number

A: The mass number is defined as the total number of protons and neutrons in an atom.
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Q: Question: At equilibrium reactants and what are equally abundant? Answer: products

A: Reactants and products are equally abundant at equilibrium.
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Q: Question: The presence of what makes soil hold together more tightly and enables it to hold more water? Answer: clay

A:
Soils with lots of very small spaces are water-holding soils. When clay is present in a soil, the soil holds together more tightly. Clay-rich soil can hold more water.
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