500mL of air are trapped in a tube over mercury at 25°C. It is found that, after six
days, the air has expanded so that 32mL have escaped the tube. What total
temperature change occurred over this period if the pressure remained constant?

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom

They can measure  the amount of energy gained or lost

Ithink about 50 % of an original isotope's number of atoms remain