Biology | Water As A Solvent
This video is all about one of water's most intriguing and fundamental properties: water as a solvent. We’ve already addressed the notion that water has some polarity to it in the previous video. One end of the molecule has a partially negative charge and the other end has a partially positive charge. We’ve talked about how this leads to hydrogen bonds when multiple water molecules are placed near each other. We also alluded to the fact that it’s these hydrogen bonds that give water many of their unique properties. So the main property that we will especially be going into detail upon is water’s ability to act as a solvent. What this means is that it’s easy for certain things to be dissolved in water. This is really important to understand because a lot of biochemical reactions occur by being dissolved in water, and then interacting with other things. This is what is constantly happening inside of cells and especially the cytoplasm. Since the majority of the cytoplasm is made of water, it acts as a solvent, which allows many interactions to happen between various types of molecules. So the key feature that makes water a good solvent for a large class of molecules is because of its polarity. For example, if you were to look at some sodium chloride, often known as table salt, you would see that the sodium and the chloride are attracted by ionic bonds. The sodium has a positive charge, which means that it has an electron taken away from it, while the chloride has a negative charge, meaning that it has taken away an electron. Like we learned in our Elements & Atoms video, these are called anions and cations. We also learned that opposing electromagnetic charges attract, which is what causes this ionic bond. We can take a closer look at both the sodium chloride and the water molecules. Since we know opposing electromagnetic charges attract, we can predict what is going to happen if sodium chloride and water interact with each other. The oxygen end of the water molecule is going to be attracted to the sodium ion. This means that the oxygen ends will go towards the sodium ion while the hydrogen ends will be repelled away from it. So when several water molecules and their oxygen ends are attracted to the sodium ion, the sodium will be able to dissolve in the water very easily since it is also attracted to the partially negative ends of the water molecules. Something similar will happen with the chloride anion as well. Since it has a negative charge, it’s going to be attracted to the partially positive hydrogen ends of the water molecules, and vice versa. So you probably see something interesting here. This is that if something has charge, such as an ion, or if something has a polarity, it’s very easy for it to dissolve inside of water, which is because the same sequence of events as we’ve just observed would occur once again. And so in the scenario that we’ve just observed, the water would be the solvent, which means that it is the substance that is dissolving something, and the sodium chloride would be the solute, which means it is the substance being dissolved. So now that we understand how hydrophilic substances are able to incorporate themselves into the water with ease and success, you might be wondering about what are some substances that aren’t able to dissolve in water very well. The answer to this is that most substances that are not polar, known as non-polar substances, aren’t going to be able to act as a solute in water very well. A good example of this is hydrocarbons. So if we looked at some hexane, which is a type of hydrocarbon and a major component of gasoline, we would see that this molecule doesn't have any polarity to it. As a result, if we threw some hexane into the water, it wouldn’t dissolve all that well as the sodium chloride would. This means that things like hexane are known as hydrophobic substances. Once again, when we look at the word it appears to mean afraid of water, as “phobic” means fear. So as we continue to indulge in biology, we will continue to see these hydrophobic and hydrophilic reactions and the sequence of steps that occur when water acts as a solvent, which we now know of. All of these assets will become very useful as we near our cells unit, but for now, I thank you all for watching. *Copyright Disclaimer Under Section 107 of the Copyright Act 1976, allowance is made for "fair use" for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational or personal use tips the balance in favour of fair use. No copyright infringement intended.* I do not own any of the images shown in this video. All rights to the images displayed belong to their respective owners.
This video is all about one of water's most intriguing and fundamental properties: water as a solvent. We’ve already addressed the notion that water has some polarity to it in the previous video. One end of the molecule has a partially negative charge and the other end has a partially positive charge. We’ve talked about how this leads to hydrogen bonds when multiple water molecules are placed near each other. We also alluded to the fact that it’s these hydrogen bonds that give water many of their unique properties. So the main property that we will especially be going into detail upon is water’s ability to act as a solvent. What this means is that it’s easy for certain things to be dissolved in water. This is really important to understand because a lot of biochemical reactions occur by being dissolved in water, and then interacting with other things. This is what is constantly happening inside of cells and especially the cytoplasm. Since the majority of the cytoplasm is made of water, it acts as a solvent, which allows many interactions to happen between various types of molecules. So the key feature that makes water a good solvent for a large class of molecules is because of its polarity. For example, if you were to look at some sodium chloride, often known as table salt, you would see that the sodium and the chloride are attracted by ionic bonds. The sodium has a positive charge, which means that it has an electron taken away from it, while the chloride has a negative charge, meaning that it has taken away an electron. Like we learned in our Elements & Atoms video, these are called anions and cations. We also learned that opposing electromagnetic charges attract, which is what causes this ionic bond. We can take a closer look at both the sodium chloride and the water molecules. Since we know opposing electromagnetic charges attract, we can predict what is going to happen if sodium chloride and water interact with each other. The oxygen end of the water molecule is going to be attracted to the sodium ion. This means that the oxygen ends will go towards the sodium ion while the hydrogen ends will be repelled away from it. So when several water molecules and their oxygen ends are attracted to the sodium ion, the sodium will be able to dissolve in the water very easily since it is also attracted to the partially negative ends of the water molecules. Something similar will happen with the chloride anion as well. Since it has a negative charge, it’s going to be attracted to the partially positive hydrogen ends of the water molecules, and vice versa. So you probably see something interesting here. This is that if something has charge, such as an ion, or if something has a polarity, it’s very easy for it to dissolve inside of water, which is because the same sequence of events as we’ve just observed would occur once again. And so in the scenario that we’ve just observed, the water would be the solvent, which means that it is the substance that is dissolving something, and the sodium chloride would be the solute, which means it is the substance being dissolved. So now that we understand how hydrophilic substances are able to incorporate themselves into the water with ease and success, you might be wondering about what are some substances that aren’t able to dissolve in water very well. The answer to this is that most substances that are not polar, known as non-polar substances, aren’t going to be able to act as a solute in water very well. A good example of this is hydrocarbons. So if we looked at some hexane, which is a type of hydrocarbon and a major component of gasoline, we would see that this molecule doesn't have any polarity to it. As a result, if we threw some hexane into the water, it wouldn’t dissolve all that well as the sodium chloride would. This means that things like hexane are known as hydrophobic substances. Once again, when we look at the word it appears to mean afraid of water, as “phobic” means fear. So as we continue to indulge in biology, we will continue to see these hydrophobic and hydrophilic reactions and the sequence of steps that occur when water acts as a solvent, which we now know of. All of these assets will become very useful as we near our cells unit, but for now, I thank you all for watching. *Copyright Disclaimer Under Section 107 of the Copyright Act 1976, allowance is made for "fair use" for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational or personal use tips the balance in favour of fair use. No copyright infringement intended.* I do not own any of the images shown in this video. All rights to the images displayed belong to their respective owners.