[3], "Surface and interfacial tension | White Paper", https://en.wikipedia.org/w/index.php?title=Meniscus_(liquid)&oldid=1152442360, This page was last edited on 30 April 2023, at 07:42. This occurs with water and a glass tube. We will not concern ourselves with calculating capillary height in this course. The meniscus of a liquid is the upward or downward curve seen at the top of a liquid in a container. Let me do it in that green color. the Terms and Conditions. In any case, you get the true volume of the liquid by reading the center of the liquid in the tube, as shown by the middle of the dashed line in the diagram. Registered in England and Wales no. Raindrops start to form in a roughly spherical structure due to the surface tension of water. The viscosity of a liquid is a measure of its resistance to flow. You can imagine now okay, maybe another water that's because it is attracted to the actual paper towel. On the other hand, water forms a concave meniscus. you spill some water, or you spill some milk. We also use third-party cookies that help us analyze and understand how you use this website. And let me make this The meniscus of water curves up the sides of the cylinder, while heavy liquids like mercury curves down the cylinder. The intermolecular forces between molecules in the liquid state vary depending upon their chemical identities and result in corresponding variations in various physical properties. going on here with the mercury, the mercury is more attracted to itself than it is to the glass container, so it bulges right over there. In anatomy and medicine, a meniscus is a crescent-shaped or semi-lunar structure that partially divides the cavity of a joint. right now, that is the water. The liquid itself is held together by its own cohesive forces. Copyright 2023 Quick-Advice.com | All rights reserved. Silicon is even less ThoughtCo, Aug. 27, 2020, thoughtco.com/definition-of-meniscus-605883. On the other hand, the cohesive forces between mercury atoms are much greater than the adhesive forces between mercury and glass. actually see in the water because there's a bigger Science Photo Library's website uses cookies. Therefore, the meniscus of water is concave. As pictured below, the volume should be read from the bottom of the meniscus. It all depends on if the molecules of the liquid are more attracted to the outside material or to themselves. This makes good sense, considering the shape of a meniscus. When you visit the site, Dotdash Meredith and its partners may store or retrieve information on your browser, mostly in the form of cookies. Mercury in a glass flask is a good example of the effects of the ratio between cohesive and adhesive forces. Both consist of long molecules of cellulose that contain many OH groups. actually are quite polar. Explanation: In the case of water, as density is low, adhesive force is more as compared to cohesive force and capillary rise will take place. The outward curve is greater than the inward curve, the lens acts as a magnifier and has a positive focal length. adhesion occurring more intensely because more of the water A concave meniscus, which is what you normally will see, occurs when the molecules of the liquid are attracted to those of the container. Alternatively for mercury, the cohesive forces are stronger than the adhesive forces which allows the the meniscus to bend away from the walls of the capillary tube. Because water adheres strongly to the polar surface of glass, it has a concave meniscus, whereas mercury, which does not adhere to the glass, has a convex meniscus. That's why you'll see On the other hand, the cohesive forces between mercury atoms are much greater than the adhesive forces between mercury and glass. Some features of this website require JavaScript. How many lines of symmetry does a star have? Tap water, containing a few dissolved chemicals, has a slightly taller meniscus, and sea water has a much taller one. and then you still have partial negative charges A convex meniscus occurs when the liquid particles are more attracted to each other than to the walls of the container. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. Explain. The reason is the flow of air around the drop. looks something like that. 8 Why does Mercury have no attraction to water? In general, the shape of the surface of a liquid can be complex. And actually it would be very hard to find something that thin that's on the order of only a few molecules. Honey, syrup, motor oil, and other liquids that do not flow freely, like those shown in Figure \(\PageIndex{1}\), have higher viscosities. Helmenstine, Anne Marie, Ph.D. (2020, August 27). This turns the meniscus in an upward direction. This is a convex, convex meniscus. And so you can imagine all of a sudden, maybe this, let me see, Capillary, capillary action. Share sensitive information only on official, secure websites. Conversely, a convex meniscus occurs when the particles in the liquid have a stronger attraction to each other than to the material of the container. When liquid mercury is confined in a tube, its surface (meniscus) has a . It forms what looks like the upper portion of a sphere - a convex meniscus. So, I fill the water right over here. Science Photo Library's website uses cookies. when it's away from the glass. If you also had glass over here. Retrieved from https://www.thoughtco.com/definition-of-meniscus-605883. Is that the reason why some water stays in a glass of water after you drink it or pour it out? and the container, also known as "wetting", encourages as much liquid US toll free: 1-844 677 4151, General enquiries: info@sciencephoto.com If the adhesive forces between water molecules and the molecules of the surface are weak compared to the cohesive forces between the water molecules, the water does not wet the surface. Get eye level with the meniscus. The mercury atoms are strongly attracted to each other by metallic bonds. clear what's going on. just jump back down. And then it's vibrating there and then maybe another water A concave meniscus occurs when the molecules of the liquid are more strongly attracted to the container than to each other. If the cohesive forces between molecules of a liquid are stronger than London Direct link to bhakti patel's post Water has hydrogen bondin, Posted 7 years ago. And I would say, "Yes, If I were to take, if I were away from the container than when you're at the container. In the case of water and most liquids, the meniscus is concave. The atoms in glass are covalently bonded together into what is effectively a giant molecule these covalent bonds are too strong to be disrupted by interaction with water molecules. So these are partial negative. It is convex when cohesion is stronger. On the. And partial positive at the silicon. (credit: Mark Ott). mercury The curved surface of a liquid inside a container is the meniscus. https://www.thoughtco.com/how-to-read-a-meniscus-606055 (accessed May 1, 2023). This is the upward or downward curve at the surface of a liquid in a container. A convex meniscus occurs when the molecules have a stronger attraction to each other than to the container, as with mercury and glass. we're in a liquid state. When you pour a glass of water, or fill a car with gasoline, you observe that water and gasoline flow freely. This is because dissolved salts can increase the surface tension of water. e.g. away from the container, we would call this a Helmenstine, Anne Marie, Ph.D. "How to Read a Meniscus in Chemistry." The cookie is used to store the user consent for the cookies in the category "Other. Science Photo Library (SPL) What is upward meniscus? expand_more See More the adhesive forces between the molecules of a liquid and those of the The liquid appears to "stick" to the edge of the container. Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features. It all depends on if the molecules of the liquid are more attracted to the outside material or to themselves. Thats what youre noticing. The meniscus can be either concave or convex, depending on the surface tension of the liquid and its adhesion to the wall of the container. Water-based fluids like sap, honey, and milk also have a concave meniscus in glass or other wettable containers. These cookies will be stored in your browser only with your consent. Direct link to haekele's post Capillary action occurs, , Posted 7 years ago. Invent and record a hypothesis to explain why liquids like water have a concave meniscus in a glass vial whereas mercury has a convex meniscus in a glass vial. So this is the glass right over here. We can measure viscosity by measuring the rate at which a metal ball falls through a liquid (the ball falls more slowly through a more viscous liquid) or by measuring the rate at which a liquid flows through a narrow tube (more viscous liquids flow more slowly). Well sure, you can have a convex meniscus. it or you won't see it if you were dealing with a plastic tube because the plastic does A meniscus is a phase boundary that has been curved because of surface tension . GB 340 7410 88. And so you can imagine we have glass here. electronegativity difference between the silicon and If the liquid molecules are strongly attracted to the tube molecules, the liquid creeps up the inside of the tube until the weight of the liquid and the adhesive forces are in balance. When you visit the site, Dotdash Meredith and its partners may store or retrieve information on your browser, mostly in the form of cookies. For every one silicon, Mercury, on the other hand, forms a convex meniscus. Please enable it in your browser. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". An official website of the United States government. The adhesive forces between the liquid and the porous material, combined with the cohesive forces within the liquid, may be strong enough to move the liquid upward against gravity. However, before we explain why some liquid have a concave up meniscus while others share a concave down meniscus, we have to understand the adhesive forces at work of surface tension.Water, for example, is a polar molecule that consists of a partial positive charge on the . In most cases, menisci are concave due to molecules of liquids more strongly attracted to the walls of the tube than to each other. A good example of this shape of meniscus can be seen with mercury in a glass container. Retrieved from https://www.thoughtco.com/how-to-read-a-meniscus-606055. Adhesion between the liquid If you place one end of a paper towel in spilled wine, as shown in Figure \(\PageIndex{5}\), the liquid wicks up the paper towel. https://www.thoughtco.com/definition-of-meniscus-605883 (accessed May 1, 2023). to take a glass tube, a thin glass tube this time. The various IMFs between identical molecules of a substance are examples of cohesive forces. This is typically done with a Wilhelmy plate.[2]. Why does Mercury have no attraction to water? GB 340 7410 88. e.g. If you take a paper towel. The formation of menisci is commonly used in surface science to measure contact angles and surface tension. Why is the meniscus of water concave and of? A meniscus is a phase boundary that has been curved because ofsurface tension. The water molecules are also attracted to each other, so large amounts of water are drawn up the cellulose fibers. to hog silicon's electrons. $\endgroup$ As Table \(\PageIndex{1}\) shows, the more structurally complex are the molecules in a liquid and the stronger the IMFs between them, the more difficult it is for them to move past each other and the greater is the viscosity of the liquid. Conversely, a concave meniscus occurs when the molecules of the liquid attract those of the container's, causing the surface of the liquid to cave downwards. cohesive forces in the liquid, likes to minimize the surface area of Beyond the fact that And so it'll stick to it. Direct link to Matt B's post Very interesting question, Posted 4 years ago. Because of its high cohesion and low adhesion to the glass, mercury does not spread out to cover the bottom of the flask, and if enough is placed in the flask to cover the bottom, it exhibits a strongly convex meniscus, whereas the meniscus of water is concave . When water is confined in a glass tube, its meniscus (surface) has a concave shape because the water wets the glass and creeps up the side of the tube. You might have even observed this before. For a concave meniscus, this it the lowest point or bottom of the meniscus. By sharing this link, I acknowledge that I have read and understand The surface tension is quite a major effect. Definition and Equations, Water Properties and Facts You Should Know, Precipitate Definition and Example in Chemistry, Chemistry Vocabulary Terms You Should Know, Examples of Physical Changes and Chemical Changes, 7 Things to Consider Before Buying a Telescope, How to Grow Crystals - Tips and Techniques, Ph.D., Biomedical Sciences, University of Tennessee at Knoxville, B.A., Physics and Mathematics, Hastings College. This, what I am circling In the figure, the capillary rise can be seen, the meniscus is in a concave shape. Depth must be measured with the meniscus at eye level (to eliminate parallax error) and at the center of the meniscus, i.e. It forms a shape that Sales enquiries: sales@sciencephoto.com Figure \(\PageIndex{1}\): (a) Honey and (b) motor oil are examples of liquids with high viscosities; they flow slowly. Capillaries are our The curve formed by the liquid is lowest . University of Illinois at Urbana-Champaign. paper towel like this. On smaller raindrops, the surface tension is stronger than in larger drops. This procedure can be easily done because of capillary action, the ability of a liquid to flow up a small tube against gravity, as shown in Figure \(\PageIndex{7}\). And you could imagine ThoughtCo. Direct link to tyersome's post The atoms in glass are co, Posted 7 years ago. The strong cohesive. In a science class, this liquid is usually water or some sort of aqueous solution, and the column is usually a graduated cylinder or a pipet. You depend on a constant supply of tears to keep your eyes lubricated and on capillary action to pump tear fluid away. Capillary action, and adhesive forces are responsible for concave meniscus and 'leftover' of water in glasses. So much thinner than even a beaker. Click here. CHARLES D. WINTERS/SCIENCE PHOTO LIBRARY. Adhesive forces between the molecules of a liquid and different molecules composing a surface in contact with the liquid are responsible for phenomena such as surface wetting and capillary rise. The cookie is used to store the user consent for the cookies in the category "Performance". And one just gets bumped the right way, jumps up and jump there. And then it's going to stick to the glass. Capillary action, Posted 7 years ago. Found a typo and want extra credit? Well this phenomenon which energy to jump up here. When the weight of the liquid in the tube generates a downward force equal to the upward force associated with capillary action, the liquid stops rising. Figure \(\PageIndex{6}\): Depending upon the relative strengths of adhesive and cohesive forces, a liquid may rise (such as water) or fall (such as mercury) in a glass capillary tube. 3-18). that looks like this where there's a bulge near the center when you're further This results in the concave formation of water in the capillary tube; this is known as capillary attraction. 327-329 Harrow Road A small tube has a relatively large surface area for a given volume of blood, which results in larger (relative) attractive forces, allowing the blood to be drawn farther up the tube. The meniscus is the curvature of a liquid's surface within a container, such as a graduated cylinder. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. If you held it vertically, molecule could jump up here and stick to the glass there. In either case, you are measuring based on the center of the meniscus. is a big tub of water. Ans: Because cohesive force between molecules of mercury is greater than the adhesive force between mercury and glass molecules. Exactly! So these things just keep bumping around. And in particular this meniscus, because the fluid is Measure the meniscus at eye level from the center of the meniscus. And so the first thing we might ask is what'll we call this thing. For a convex meniscus, this is the uppermost or top point of the liquid. Water has hydrogen bonding.what about mercury?does mercury repel glass tube?what is the force which makes mercury have more cohesive nature than adhesive nature? It has to be a polar material. It all depends on if the molecules of the liquid are more attracted to the outside material or to themselves. Surface energies, surface tensions, contact angles, all related. Water-based fluids like sap, honey, and milk also have a concave meniscus in glass or other wettable containers. I had one question though - at aroung 8:6 in the video, Sal begins describing how water can soak upwards in a paper towel because of capillary action. This may be seen between mercury and glass in barometers and thermometers. The meniscus is the curve seen at the top of a liquid in response to its container. Eventually the force of gravity balances out the forces pulling the water upwards and it stops. And just to be clear what's The extent of the rise (or fall) is directly proportional to the surface tension of the liquid and inversely proportional to the density of the liquid and the radius of the tube. Mercury produces a convex meniscus. Direct link to Pdogg's post Khan said that the reason, Posted 4 years ago. The meniscus is the curve seen at the top of a liquid in response to its container. Water meniscus is convex, mercury menisucs is concave A meniscus can go up or down. CHARLES D. WINTERS/SCIENCE PHOTO LIBRARY Necessary cookies are absolutely essential for the website to function properly. Mercury shows a convex meniscus (the centre is higher than the edges), because internal cohesive forces are stronger than the force between the glass wall and the metal. (credit photo: modification of work by Mark Blaser). Convex menisci occur, for example, between mercury and glass in barometers[1] and thermometers. 1550520. How to Read a Meniscus in Chemistry. But it's actually not the case and I encourage you to try it. By continuing, you agree to accept cookies in accordance with our Cookie policy. Why is the surface of water in glass tubes curved? (credit photo: modification of work by OliBac/Flickr). Cookies collect information about your preferences and your devices and are used to make the site work as you expect it to, to understand how you interact with the site, and to show advertisements that are targeted to your interests. maybe this character, this water molecule right over here. A convex meniscus occurs when the molecules have a stronger attraction to each other than to the container, as with mercury and glass. In a contact angle measurement, the shape of the menisci is measured with a balance or optically with a digital camera. Most cloth towels are made of cotton, and paper towels are generally made from paper pulp. Click here. Case I: The Meniscus. Menisci are a manifestation of capillary action, by which either surface adhesion pulls a liquid up to form a concave meniscus, or internal cohesion pulls the liquid down to form a convex meniscus. However the video did also say that capillary action can only occur with an polar compound as a surface. This makes taking measurements easy. So why do, Posted 5 years ago. That also explains why the meniscus is concave. Why does mercury have a convex meniscus while water is concave? that's the water molecules. A meniscus is a curved liquid surface that results from the interplay of adhesion (the liquid's attraction to its container) and cohesion (the liquid's attraction to itself). This phenomenon is important in transpirational pull in plants. is called a meniscus. The water is seen to curve up the edge of the glass. A huge thanks to Sal and the Khan Academy Team for putting togather this informative video. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Direct link to kayla gilbreath's post What would happen if you , Posted 7 years ago. A meniscus lens is a convex-concave lens in which one face curves outward, while the other face curves inward. As a result of this high surface tension, the surface of water represents a relatively tough skin that can withstand considerable force without breaking. In the case of water and mostliquids, the meniscus is concave. Direct link to Just Keith's post That is called a convex m, Posted 5 years ago. For every one silicon atom, Direct link to Learner's post Glass is polar. You can read about more in-depth here: Khan said that the reason for the concave meniscus in a glass tube was the water molecules bonding with the glass molecules. Cohesive forces between like molecules are responsible for a liquids viscosity (resistance to flow) and surface tension (elasticity of a liquid surface). not have that polarity. This cookie is set by GDPR Cookie Consent plugin. 2 How is the meniscus of mercury different to that of water? The meniscus is the curving of water at the surface due to its surface tension, the attraction of molecules for each other. What Is Centripetal Force? A flat meniscus occurs when water in some types of plastic tubes; tubes made out of material that water does not stick to. The height to which a liquid will rise in a capillary tube is determined by several factors as shown in the following equation: \[h=\dfrac{2T\cos}{rg} \label{10.2.1}\], Applications: Capillary Action is Used to Draw Blood. But when you pour syrup on pancakes or add oil to a car engine, you note that syrup and motor oil do not flow as readily. Example: Mercury (when exposed to air, 138 with glass) Flat Meniscus: The contact angle, , for a flat meniscus is 90. container then you will see a "convex meniscus."

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