Because you need to know what you are looking for before actually trying something so you can prevent any accidents by doing stuff at random

An atom of this isotope contains 5 protons and 10-5=5 neutrons.

The answer is A. 1.67 × 10⁻²⁶ kg.
Explanation:
When experimenting, the best hypothesis to develop would be a null hypothesis (H₀). A null hypothesis is a statement indicating no change or effect. In this case, it would be;
“There is no effect of temperature on the solubility of a solid in a liquid”
An alternative hypothesis (Hₐ) would be;
“There is an effect of temperature on the solubility of a solid in a liquid”
In this experiment, the null hypothesis would be rejected and the alternative would be accepted. This is because the experiment would show that increased temperatures of the liquid increases solubility of the solid in the liquid.
I really don’t know the answer, please help this kiddo with his question