Physical properties are used to classify and compare substances. Physical properties can include density, thermal conductivity, electrical conductivity,
solubility, magnetism, melting point, and boiling point. Which statement is
correct about all of these physical properties?
They involve a change in the state of matter.
They involve the production of new substances.
They can be measured only after a change in state.
They are independent of the amount of the sample present.

Physical properties involve a change in the state of matter.

Explanation:

A chemical change would change the chemical composition.

A physical change would change the state of matter, for example solid to liquid to gas are changes in state. So, this means when water changes states of matter it is a physical change.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.