meniscus of water and mercury

A huge thanks to Sal and the Khan Academy Team for putting togather this informative video. 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. e.g. Glass, typically made up the meniscus in glass, but you might not see Option C is correct. A flat meniscus occurs when water in some types of plastic tubes; tubes made out of material that water does not stick to. This website uses cookies to improve your experience while you navigate through the website. The liquid itself is held together by its own cohesive forces. For water, adhesive force is stronger than the cohesive forces, sticking more strongly to the capillary wall than other water molecules, hence as the tube is thinner, the higher the level. on a very thin glass tube. However the video did also say that capillary action can only occur with an polar compound as a surface. Cohesive and Adhesive Forces - Chemistry LibreTexts When you have mercury liquid in a container, why is the meniscus upside down compared to all other liquids? On the. This is the situation for water rising in a glass tube. drawing things in scale. This cookie is set by GDPR Cookie Consent plugin. up this thin glass tube. Concave Meniscus: Meniscus and Wetting. Water, Alcohol and Mercury. - YouTube Who invented Google Chrome in which year? When you talk about 3-18). The mercury atoms are strongly attracted to each other by metallic bonds. 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. In physics, the term "meniscus" can either apply to the boundary between a liquid and its container or to a type of lens used in optics. when it's away from the glass. 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. You can either pick up the glassware to bring it to your level or else bend down to take measurements in situations where you're concerned with dropping the container or spilling its contents. A concave meniscus, which is what you normally will see, occurs when the molecules of the liquid are attracted to those of the container. Mercury has a convex meniscus because the intermolecular forces between mercury atoms are stronger than those between mercury atoms and glass molecules of a tube. In general, the shape of the surface of a liquid can be complex. Convex menisci occur, for example, between mercury and glass in barometers[1] and thermometers. 4: The Phenomenon of Capillary Action. If the cohesive forces between molecules of a liquid are stronger than But this is, I'm not Most cloth towels are made of cotton, and paper towels are generally made from paper pulp. The various IMFs between identical molecules of a substance are examples of cohesive forces. VAT no. 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. This cookie is set by GDPR Cookie Consent plugin. Figure \(\PageIndex{4}\): Differences in the relative strengths of cohesive and adhesive forces result in different meniscus shapes for mercury (left) and water (right) in glass tubes. So, I fill the water right over here. Let me do it in that green color. University of Illinois at Urbana-Champaign. It is called a meniscus. it kind of just stuck to it. So let's say that this When the molecules of the liquid have a greater attraction to the cylinder wall than to themselves, the meniscus is concave and the surface of the liquid curved downwards. why it is going to be more attracted to the glass than itself, because glass actually has, the molecules in glass 21.4 MB (1.5 MB compressed) 2377 x 3148 pixels. A meniscus occurs because of surface tension. Then it gets bumped the right way. 6 Why does liquid rise in a capillary tube? Many medical tests require drawing a small amount of blood, for example to determine the amount of glucose in someone with diabetes or the hematocrit level in an athlete. 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. it's actually happening in your capillaries in your Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. When you pour a glass of water, or fill a car with gasoline, you observe that water and gasoline flow freely. It does not store any personal data. But let's go back to water. 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. A meniscus is a phase boundary that has been curved because ofsurface tension. the Terms and Conditions. this concave meniscus is because the fluid is more attracted to the container than it is to itself. Helmenstine, Anne Marie, Ph.D. (2020, August 28). This occurs with water and a glass tube. The viscosity of a liquid is a measure of its resistance to flow. GB 340 7410 88. This is a convex, convex meniscus. A convex meniscus (sometimes called a "backwards" meniscus) is produced when the molecules of the liquid are more strongly attracted to each other than to the container. Cohesive forces between like molecules are responsible for a liquids viscosity (resistance to flow) and surface tension (elasticity of a liquid surface). Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. When you visit the site, Dotdash Meredith and its partners may store or retrieve information on your browser, mostly in the form of cookies. The meniscus is convex and the surface of the liquid inside the tube is lower than the level of the liquid outside the tube. the small little gaps of the paper towel, but Water meniscus is concave, mercury meniscus is convex. In physics (particularly fluid statics), the meniscus (plural: menisci, from Greek'crescent') is the curve in the upper surface of a liquid close to the surface of the container or another object, produced by surface tension. In the case of the meniscus, equilibrium between the surface energies of the gas, solid and liquid. Direct link to levongalstyan98's post Most cloth towels are mad, Posted 7 years ago. So let me write this down. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. something on your counter. She has taught science courses at the high school, college, and graduate levels. Water molecules are attracted to these OH groups and form hydrogen bonds with them, which draws the H2O molecules up the cellulose molecules. Some liquids, like the element mercury (Hg), form a convex meniscus, meaning that it is shaped like a lower-case n (see Fig. Capillary Action - Chemistry LibreTexts it's more attracted to the glass than it is to itself?" Both consist of long molecules of cellulose that contain many OH groups. How to Read a Meniscus in Lab Measurements - ThoughtCo It all depends on if the molecules of the liquid are more attracted to the outside material or to themselves. Why does Mercury have no attraction to water? The only part of the moons gravitational pull that has any effect is the difference in its strength over the different parts of the glass. over here, the glass molecules. Partial positive charges at the hydrogens. In the case of water and mostliquids, the meniscus is concave. Please enable it in your browser. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. In fact, if you took a It has to be a polar material. And let's say I take a glass tube, and the material matters. you have two oxygen atoms. She has taught science courses at the high school, college, and graduate levels. As you may have noticed, when water is in such a thin glass tube, it does not have a flat surface at the top. 7.1: Surface Tension, Viscosity, and Capillary Action (Problems), http://cnx.org/contents/85abf193-2bda7ac8df6@9.110, Distinguish between adhesive and cohesive forces, Define viscosity, surface tension, and capillary rise, Describe the roles of intermolecular attractive forces in each of these properties/phenomena, Adelaide Clark, Oregon Institute of Technology, Crash Course Chemistry: Crash Course is a division of. And so you can imagine we have glass here. A lock () or https:// means youve safely connected to the .gov website. And you could imagine Explanation: The shape of the meniscus, of a given liquid, in a given container, is determined primarily by the comparative magnitudes of the relevant forces of cohesion and adhesion. If you were take that same glass beaker, instead of filling it with water if you filled it with say, mercury. The meniscus (plural: menisci, from the Greek word for crescent) is the curve in the upper surface of a liquid close to the surface of the container or another object, caused by surface tension. https://www.thoughtco.com/definition-of-meniscus-605883 (accessed May 1, 2023). On the other hand, water forms a concave meniscus. Rights Managed. Explain why the meniscus of water is concave and that of mercury is When mercury is placed in a graduated cylinder, the cohesive forces in the mercury are stronger than the adhesive forces between the mercury and the glass. Legal. "We've been talking about how water "has this polarity, it You can find out more about our use, change your default settings, and withdraw your consent at any time with effect for the future by visiting Cookies Settings, which can also be found in the footer of the site. Mercury, being much more dense has no such attraction because it is a liquid metal.Answer:It is due to what is called cohesion and adhesion. spill right over there. Direct link to haekele's post Capillary action occurs, , Posted 7 years ago. W9 3RB And so it starts climbing the container. you spill some water, or you spill some milk. The meniscus is the curve seen at the top of a liquid in response to its container. Example: Mercury (when exposed to air, 138 with glass) Flat Meniscus: The contact angle, , for a flat meniscus is 90. Meniscus in mercury (left) and water compared. 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 . Consider what happens when water comes into contact with some surface. This is the upward or downward curve at the surface of a liquid in a container. When liquid mercury is confined in a tube, its surface (meniscus) has a . 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. electronegativity difference between the silicon and When you read a scale on the side of a container with a meniscus, such as a graduated cylinder or volumetric flask, it's important that the measurement accounts for the meniscus. 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. 3 When mercury is kept in glass meniscus is? These are examples of capillary actionwhen a liquid flows within a porous material due to the attraction of the liquid molecules to the surface of the material and to other liquid molecules. Direct link to Matt B's post Very interesting question, Posted 4 years ago. Meniscus of Water & Mercury. The concave meniscus of water and convex meniscus of mercury are shown in the figure below. But it's one thing to just By continuing, you agree to accept cookies in accordance with our Cookie policy. Direct link to Ivana - Science trainee's post First: the chemical compo, Posted 7 years ago. In either case, you are measuring based on the center of the meniscus. Model release not required. 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. to hog silicon's electrons. but then it sticks there. Meniscus of Water & Mercury - Stock Image - C036/3355 29,306 views Apr 3, 2014 Meniscus and wetting are caused by surface tension. Helmenstine, Anne Marie, Ph.D. "How to Read a Meniscus in Chemistry." University of Illinois at Urbana-Champaign, Absorption and scattering of light in air. The meniscus (plural: menisci, from the Greek word for crescent) is the curve in the upper surface of a liquid close to the surface of the container or another object, caused by surface tension. gets knocked up here. thats if the liquid molecules stick to each other better than they 7.1: Surface Tension, Viscosity, and Capillary Action What is Meniscus? This turns the meniscus in an upward direction. Water, Alcohol and Mercury. we call capillary action. But let's say you were 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. When a glass capillary immersed in water, the meniscus is concave upwards. Measure the meniscus at eye level from the center of the meniscus. (In other words, You spill some maybe, Science Photo Library (SPL) For a convex meniscus, this is the uppermost or top point of the liquid. body that allows you to live, but if you have a, if you spill (credit a: modification of work by Scott Bauer; credit b: modification of work by David Nagy). Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. 12201 Sunrise Valley Drive Reston, VA 20192. Powered by SiteManager | Contact Webmaster. 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. higher near the container than it is when you're to take a glass tube, a thin glass tube this time. For every one silicon atom, 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). concave, concave meniscus. When a tube of a narrow bore, often called a capillary tube, is dipped into a liquid and the liquid wets the tube (with zero contact angle), the liquid surface inside the tube forms a concave meniscus, which is a virtually spherical surface having the same radius, r, as the inside of the tube.

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