substance

  1. K

    Equation for chemical potential of pure substance. Unsure why this derives as it does

    Hello, I am new to this. I have attached a screenshot from a journal article which talks about deriving Fick's first law. My calculus is a little rusty, and I don't understand how equation 5 is derived from equation 4. I'd have a go, but I have little to offer. All I have to offer is...
  2. J

    Defining substance

    I’m fairly new to the world of physics but am extremely intrigued by many of its various fields. Most recently I have been struggling to find a clear answer as to what determines if something has substance. My novice assumption would be that substance can be defined by its interaction with...
  3. L

    Half life of substance

    cancer a patient who is undergoing cancer theraphy is given 10 mins of irradiation from a radioactive source that has half life = 2 years. If the same source is to be used for same treatment 2 years later , how long should the patient should be irradiated? the ans is 20 mins .. can someoene...
  4. A

    Calculate the net charge on a substance consisting of a combination of 7.8 1013 prot

    Calculate the net charge on a substance consisting of a combination of 7.8 1013 protons and 3.0 1013 electrons.