Learn about Junior Chemistry, Solutions 1, in this comprehensive video by bannanaiscool.
Read the full transcript »
Male Speaker: There is some salt in this beaker, some sugar in here and know that this is ionic and this is molecular. Now we are going to make solutions out of both of these compounds and we are going to test these solutions for electrical conductivity. We are going to use this little handy-dandy meter which will tell us if a solution is conducting or not when the two probe wires down here are touching together little like, beep the sound is all me by the way comes on and you are able to tell whether a solution actually has the ability to be able to send the electrical current from one electrode to the other complete a circuit and light up the little bulb. So, let's test it. Alright, here is the sodium chloride, here is the CO, look at that, you put the conductivity apparatus in there and it really does a job of showing conductivity. Now rinse off the electrode here in water and of course you dint see the bulb come on because water is not going to conduct and then we put the conductivity apparatus in the sucrose and we don't get seem to get any kind of a reaction there, rise it off over here, hey lets try a little bit of vinegar too and instead of throw that in there and well yup there we go, conductivity there in the acid, in the sodium chloride, nothing in the water or in the sucrose solution, lets talk. Conductivity is one type of property the solutions can have. There are other types of properties that solutions can have as well will go over there right now. So, first of all you saw in the demonstration, I know you have got good eyes so you probably aware that on in the water and in the sucrose there was slight conductivity. You know if you cant get a solution properly to still that 100% and there are some ions floating around, you are going to get conductivity and that's a big thing right here right now to differentiate between ionic and molecular solution. So the molecular, molecular solutions are non-electrolytes and that means that they do not conduct an electrical current, water into pure state doesn't really conduct very well at all and of course the sucrose being a molecular compound dissolved in the water doesn't conduct very well either. Most molecular solutions are colorless in nature and molecular compounds form solutions. Now neutral ionic that's another category of solutions. Neutral ionic, they are electrolytes you saw that the salt in water was an electrolyte. That was a conducting solution, and its also the neutral ionic, in that its pH is seven, any time you have ions like chloride iodide, bromide in solution or nitrate ion, they are going to give you solutions that when bonded to a cation that's a positive charge ion like a group 1A or 2A element, you are going to get yourself a neutral compound of pH 7 but ionic in that it conducts. Then other types of solutions will be things like acids, acids are electrolytes as well, you saw that the acetic acid conduct it. Now acetic acid wouldn't actually conduct as well as a sulphuric acid, perchloric acid, nitric acid, hydriodic acid, hydrobromic acid or hydrochloric acid, those are the six strong acids and they are strong electrolytes but the acetic acid that you saw was not a strong electrolyte although it lit up pretty well. So, acids however do all have a pH of less than seven and there are all electrolytes but some are strong and some are weak electrolytes. The strong electrolytes are strong acids, the weak electrolytes are called weak acids. And then you got bases, then give you demonstration of a base but bases have a pH its greater than seven and their electrolytes too. So, you know the one diagnostic characteristic a feature that totally describes a molecular solution is that they don't conduct. If you put a conductivity apparatus into a solution it doesn't conduct, it's molecular, everything else will conduct and it will either be neutral ionic, an acid or base.
Copyright © 2005 - 2015 Healthline Networks, Inc. All rights reserved for Healthline.