Why is the wavelength of 633 nm used to analyze the standard solutions and drink samples?

Idon’t understand this page, can someone ?

What is the mass of 8 moles of sodium atoms

Melting and boiling are endothermic processes. this means that these processes absorb energy from their surroundings in order to occur. use this information and the data you collected in the phase change gizmo to describe what happens to the temperature of water when you boil it, then explain why this result occurs.