What are some common properties of calcium , gold , iron , and sodium ?

What is relative velocity? in which condition is relative velocity known by adding the velocity of the first body and that of the second body

An element becomes a positively charged ion when itloses protons.loses electrons.gains electrons.gains neutrons.

Awelder using a tank of volume 7.50×10^-2 m^3 fills it with oxygen (with a molar mass of 32.0 g/mol ) at a gauge pressure of 3.30×10^5 pa and temperature of 37.1 ∘c. the tank has a small leak, and in time some of the oxygen leaks out. on a day when the temperature is 23.1 ∘c, the gauge pressure of the oxygen in the tank is 2.00×10^5 pa . a) find the initial mass of oxygen. b) find the mass of oxygen that has leaked out.