How does uncertainty apply to chemists?
Uncertainty applies in the sense that we as human beings are naturally imperfect. We will always have some form of uncertainty in any experiment we do, no matter how well we take precautions to not, so we should state how uncertain we are.
I will first assume that we are talking about random error and systematic error, and then proceed to the Heisenberg Uncertainty Principle.
Random error will always happen to some extent. If you do multiple trials, there is always the chance you will make human mistakes, such as with stopwatching or with measuring a specific mass onto a scale.
For example, timing is difficult to get spot-on.
The smaller the time-scale, the more difficult it is to be very precise.
Maybe you time
Or, maybe you try to measure a small mass, which can be difficult to get spot-on as well.
The smaller the mass, the greater the uncertainty you have.
For example, I have had to measure a few
Systematic error is when something is wrong with your measurement tool, and it is consistently off.
Maybe you consistently measured distance from a specific reference point, and are precisely
Or, maybe something more subtle is that you are wearing nitrile gloves and using a chemistry lab-grade scale. You'll introduce static onto the scale, which will cause the scale to display a continuously changing mass that is not accurate to your actual mass. This is called mass hysteresis.
To avoid this, you may have a static gun in the lab that you can use to remove the static. Then, you can take off your nitrile gloves and measure without gloves, and the scale shouldn't drift so much this time.
Consistency in measuring masses is especially an issue on small scales (such as a
#mu#-scale), because, wouldn't you know it, dust that you might not know is there can significantly alter your #%#accuracy.
HEISENBERG UNCERTAINTY PRINCIPLE
The Heisenberg Uncertainty Principle basically states that the more certainty
#\mathbf(DeltaxDeltap_x <= ℏ)#
#ℏ = h//2pi#is the reduced Planck's constant.
In a sense you have already seen sprinkles of this in this answer up above when I mentioned that smaller masses and smaller time scales lead to greater uncertainty.
In fact, a similar concept applies here.
In general, we usually are more certain (have lower uncertainty) about the momentum of an electron, so we tend to have high uncertainty about its position (Inorganic Chemistry, Miessler et al.).
We kind of get around that by making radial probability density plots to probabilistically define locations where an electron is statistically expected to be.
To read this plot, it just says that the greatest chance you will have of finding electrons is at ~
You have no chance of finding electrons at ~
(Obviously there is no chance either if you are completely outside the orbitals, e.g.