Select all the correct answers.

Why do the atoms in a piece of copper metal have no net charge?

The charges of the positive and negative copper ions cancel each other out.
The number of electrons surrounding each copper nucleus doesn’t change.
Copper atoms can’t lose electrons without a substance present to gain electrons.
When a copper atom loses electrons, it also loses a corresponding number of protons.
The copper atoms exchange neutrons instead of electrons.

8 m/s because for him to get the same amount of energy as ray is putting out, bobby, who weighs half as much as ray, needs to run twice as fast.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.