Solutions (Terminology)

Summary

The transcript discusses the terminology related to solutions in the field of physical chemistry. It begins with the definition of a solution, emphasizing the homogeneous mixture of solutes and solvents, such as sugar dissolved in water. Different types of mixtures are explored, including immiscible liquids like oil and water, and emulsions like milk where fat is not homogeneously dispersed. The conversation also touches on solid solutions such as alloys like brass and other phases of solutions, including gases and liquids like carbonated water and alcoholic beverages. The lecture sets the stage for deeper exploration into the properties and concentrations within multi-component systems.

Highlights

• Sugar water is a classic example of a homogeneous solution. 🍬
• Oil and water illustrate immiscible liquids that form layers instead of solutions. 🌊
• Milk is not a true solution but an emulsion with fat clusters. 🥛
• Brass, an alloy, showcases a solid solution of copper and zinc. ⚙️
• Carbonated water demonstrates gases can dissolve in liquids. 🍾

Key Takeaways

• Solutions are homogeneous mixtures where one substance is evenly dispersed within another. 🎨
• Solutes are the minority component in a solution, while solvents are the medium where solutes dissolve. 🧪
• Not all mixtures are solutions; immiscible liquids like oil and water don't qualify. 🚫
• Emulsions, like milk, have components not fully mixed on a microscopic level. 🥛
• Solutions aren't limited to liquids; solid solutions, such as alloys, exist too. 🚀
• Gas can be a solute in a liquid solution, like carbonated water. 🥤
• Understanding solution terminology is vital for exploring multi-component thermodynamics. 📚

Overview

In the realm of physical chemistry, understanding the nuances of multi-component systems is crucial. A significant portion of these systems can be classified as solutions, where one substance is uniformly distributed within another. For instance, when sugar is fully dissolved in water, it forms a solution characterized by its homogeneous nature. From here, the discourse delves into essential terminology and classifications that separate solutions from other mixtures.

Not all mixtures fit the criteria for solutions. The discussion highlights immiscible liquids, like oil and water, which refuse to blend and settle in separate layers, defying the solution status. Additionally, it explores emulsions, such as milk, where components are mixed but not uniformly at the microscopic level, indicating a more complex composition than a simple solution.

Expanding beyond liquid solutions, the lecturer touches on alloys like brass, which serve as examples of solid solutions. The conversation also underscores the versatility in solution phases, mentioning gas-in-liquid solutions like carbonated beverages. This foundational knowledge sets the stage for further analysis of solution properties and the dynamics within multi-component systems.

Chapters

• 00:00 - 00:30: Introduction to Multi-Component Systems and Solutions This chapter introduces the concept of multi-component systems and solutions, focusing on how these systems consist of various components. It emphasizes the importance of understanding terminology and vocabulary related to solutions. The discussion opens with a consideration of what constitutes a multi-component system, particularly highlighting solutions, and sets the foundation for delving deeper into topics regarding their composition and description.
• 00:30 - 02:30: Definition and Characteristics of Solutions This chapter introduces the concept of a solution. A solution is defined as a mixture of two substances where one substance is homogeneously dispersed within the other. An example provided is sugar dissolved in water, which forms a uniform solution. This sets the foundation for understanding different characteristics of solutions in subsequent sections.
• 02:30 - 03:30: Solutes and Solvents in Solutions This chapter explores the concept of solutions, focusing on the relationship between solutes and solvents. Using the example of sugar dissolving in water, it illustrates the nature of homogeneous mixtures, where the solute (sugar) is evenly distributed throughout the solvent (water). This even distribution is consistent across all scales, ensuring that any part of the solution contains equivalent proportions of solute and solvent molecules. The chapter highlights the importance of homogeneity in defining solutions.
• 03:30 - 05:30: Examples of Non-Solutions and Emulsions The chapter discusses the concept of solutions, focusing on solutes and solvents. It explains that in a solution, the solute is the substance in the smaller proportion, like sugar, and the solvent is the substance in the larger proportion, like water. It highlights the uniform distribution of solute molecules within the solution.
• 05:30 - 06:30: Emulsions and Milk as an Example In this chapter, the focus is on understanding emulsions, using milk as a primary example. The discussion highlights the difference between solutions and other types of mixtures, such as emulsions. A solution is defined as a homogeneous mixture where the solute is completely dissolved in the solvent, like sugar water. However, not all mixtures are solutions. For instance, mixing oil and water creates an emulsion rather than a solution, as they do not dissolve into each other. This concept is illustrated through the example of making salad dressing, which typically involves mixing oil and vinegar, resulting in an emulsion.
• 06:30 - 07:30: Expanding the Concept of Solutions Beyond Liquids In this chapter, the concept of solutions is extended beyond just liquid mixtures. An example is given using oil and water, which when shaken, might temporarily appear as a homogeneous mixture but will eventually separate, indicating it's not truly homogeneous. Therefore, it's more accurately described as a mere mixture rather than a solution.
• 07:30 - 10:30: Different Phases of Solutions The chapter 'Different Phases of Solutions' discusses why oil and water do not form a homogeneous mixture, highlighting the concept of immiscibility. Immiscibility refers to the inability of two substances to mix and create a solution. It is emphasized that oil is insoluble in water, leading to their separation when combined.
• 10:30 - 11:30: Conclusion and Next Topics: Concentration The chapter explores the concept of solubility with food-related examples. It explains that oil is insoluble in water, whereas sugar is soluble. The chapter also mentions milk as a complex mixture of various components, illustrating another example of mixtures.

Solutions (Terminology) Transcription

• 00:00 - 00:30 [Music] so as we begin to think about how to talk about multi-component systems systems with more than one component in them an awful lot of interesting multi-component systems are solutions can be described as solutions so let's make sure we understand the terminology how to use some vocabulary that we use to describe solutions
• 00:30 - 01:00 typically so first question is maybe what is a solution so a solution is a mixture of two substances in which importantly one substance is homogeneously dispersed within the other so you're familiar with solutions let's take as our first example um i don't know let's say sugar and water so if you just dissolve some sugar in water you've created a solution
• 01:00 - 01:30 let's say homogeneous mixture and the reason we can call this a solution is because after i've stirred the sugar into the water the the sugar molecules are dissolved in the aqueous solution they're homogeneously dispersed everywhere i look i can find an equal proportion of sugar molecules and water molecules in that mixture in that solution so since the mixture is a homogeneous mixture at every length scale no matter how finely i look i get an equal
• 01:30 - 02:00 proportion of the same proportion of sugar molecules in every portion of that solution so that's what a solution is we often talk about solutions in terms of solutes and solvents the solute is usually considered to be the minority component of that solution if i dissolve a small amount of sugar in a larger amount of water we say that the sugar is the solute the water is the solvent so the solvent is the the background
• 02:00 - 02:30 into which i'm dissolving the solute to make this homogeneous mixture that i'm calling a solution so not everything is a solution of course and i can give you some counter examples so sugar water i'll say is a solution if i mix other things with water they may not form a solution if i mix oil and water let's say you mix yourself some salad dressing which i guess would be oil and vinegar
• 02:30 - 03:00 same idea but let's just mix two component solution oil and pure water i can shake them up like you would with a salad dressing for example and get them to appear to mix but if i let them rest of course the the oil and the water will separate the oil will float on top of the water so the fact that it doesn't remain dissolved the the two separate from one another means the mixture is not homogeneous there's oil on the top and and water on the bottom so that's not a homogeneous mixture i can um call it a mixture perhaps but i
• 03:00 - 03:30 can't call that a solution that's not a solution because the oil doesn't dissolve in the water it doesn't mix homogeneously with the water terminology we would use in that case is to say those two fluids those two liquids are immiscible which just means not mixable i can't mix the oil in the water to form a solution they will separate from one another so they're immiscible i can also say that one of them is insoluble in the other
• 03:30 - 04:00 if i can't dissolve oil in water then it's oil is insoluble in water i can dissolve sugar in water so that's sugar is soluble in water let's do another food related example so here's another mixture milk is actually a very complicated mixture with lots of components of course and it certainly looks like one
• 04:00 - 04:30 solution it won't separate the way oil and water will your milk sitting in your refrigerator is uh going to remain some substances mixed throughout other ones some fat if you have uh full fat milk mixed throughout the water that is the solvent of the milk mixture but in fact this is not a solution may be difficult to tell with the naked eye but if you look very closely especially under some magnification what
• 04:30 - 05:00 you'll see is there's globules or clusters of fat molecules near each other and other regions that are mostly aqueous so the fat is not homogeneously dispersed throughout the solvent but it's located in little pockets throughout the solvent so the fact that it's not perfectly homogeneously mixed means that we don't actually call milk a solution we would call that an emulsion so if we manage to get the fat
• 05:00 - 05:30 not separating not not floating on top of the water well distributed throughout the entire sample but uh persisting in in clusters like dissolving like the oil sticking with the oil and the the water sticking with the water and clusters separated from one another we typically call that an emulsion and there's interesting chemistry to explore about how it is the fat becomes suspended within that emulsion without fully dissolving
• 05:30 - 06:00 but we'll postpone those for another day and in order to talk about more features of solutions and and we can also talk about what phases the solution has to have so everything i've talked about so far has been liquids sugar water oil and water milk those are all liquids solutions don't actually have to involve liquids let's say i have a solid chunk of brass brass it turns out
• 06:00 - 06:30 is what we call an alloy an alloy is a mixture of more than one metal so this is a binary alloy composed of two different metals if i mix the correct proportions of copper and zinc they will essentially dissolve one another if i have a homogeneous mixture of copper and zinc normally we would call that an alloy it's a little bit unusual to call it a solution but it's certainly possible to call that a solid solution we can say that brass is a solid
• 06:30 - 07:00 solution of copper and zinc so you don't have to have uh solutions that are composed purely of liquids although that's the the more traditional uh case where you'd use the terminology of a solution and in fact when we're thinking about phases although the solvent is usually but not always a liquid we can dissolve any sort of material in that liquid solvent to obtain a solution so for example
• 07:00 - 07:30 we've we've talked about several examples up here of solutions of in fact i'll come back to this one of liquids here's an example if i have carbonated water the way to prepare carbonated water the solute was originally in carbon dioxide probably in the gaseous phase if i take gaseous carbon dioxide and dissolve it in water what i get is a
• 07:30 - 08:00 solution of co2 in water or perhaps the chemical byproducts that co2 produces when it dissolves in water but the point is i've dissolved a gas in a liquid to make that solution if i want to dissolve a liquid in another liquid maybe an example i could use here would be any sort of alcoholic beverage so that is typically have more than
• 08:00 - 08:30 two components but if i take ethanol and i dissolve it in water in some proportions then i've got an alcoholic beverage alcoholic beverages not pure water they're not pure ethanol they're a solution of ethanol and water so that's an example where a liquid has been dissolved in another liquid here's a gas dissolved in another liquid we've seen one example where we have a solid dissolved in a liquid i can give a different example salt water ocean water
• 08:30 - 09:00 would be solids like sodium chloride or other salts dissolved in water so the phase of the solute before you dissolve it in the solution before you prepare the solution might have been a gas might have been a liquid might have been a solid completely irrelevant what the phase of the the solute is before it dissolves it might end up in a liquid solution in some cases we might even talk about solid solutions so those are
• 09:00 - 09:30 several terminological features of solutions that are important to be able to talk about as we move forward and talk about multi-component thermodynamics and what we'll do next is move on to talk about how to talk about the properties of a solution in particular we need to be able to talk about not just what the components of a solution are but the relative amounts of those two components so we need to be able to talk about concentration that's coming next