I’ve been reading about HL, but I still don’t get why would you use it. So, if half life of coffee is 5h, how that info is relevant when we know that full life is 10 (roughly)? On top of that, how do you get the half-life of a material other than waiting to be completely ‘dead’ and say, ok full life is X, the half life is X/2.
Also, let’s take uranium which in Earth’s crust has a half-life of almost 4.5 billion years.. how did we get this number?
Thank you!
In: Chemistry
We use half-lives when the decay rate is random but follows a predictable distribution. We don’t actually know when the “full-life” is, because it’s impossible to predict thanks to the process being random, but we can use the average time of decay to predict [a curve](https://ohiostate.pressbooks.pub/app/uploads/sites/205/2019/08/hypothetical-distribution-half-lives-.png) which tells us when half of the remaining substance will have decayed. And then it takes another half-life for half of that remaining half to decay, and so on.
So for Uranium-238 for example the process of decay for every single atom is random. In a given sample, some of the atoms will decay tomorrow, some won’t decay for the next 10 billion years. But if you have 1 kg of Uranium that’s 2.53×10^24 atoms, a very very large number, so even with the very small chance for any given atom to decay in any given second, you can still observe thousands and thousands of decays over any measurable period of time. Maybe millions, I don’t know, I can’t math. But you can do this experiment and observe how many decays your 1 kg experiences over a set period of time and from that extrapolate the half life
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