What is Liquid: Definition and 1000 Discussions

A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, and plasma), and is the only state with a definite volume but no fixed shape. A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular bonds. Like a gas, a liquid is able to flow and take the shape of a container. Most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, leading to wetting phenomena. Water is, by far, the most common liquid on Earth.
The density of a liquid is usually close to that of a solid, and much higher than in a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids. Although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is in gaseous form (with traces of detectable solid matter) as interstellar clouds or in plasma from within stars.

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  1. G

    I Pascal's law (fluids): Derivable from fundamental laws?

    Hi. Pascal's law states that static pressure in a confined incompressible fluid without gravity is the same everywhere. Is this law derivable from more fundamental laws? Some thoughts: Is Pascal's law part of the definition of the liquid state? If the liquid operates between two hydraulic...
  2. Logic hunter

    B How does liquid starts moving when there is Pascal's law

    Consider a conventional U-tube with both the vertical tubes having the same uniform cross section area A and the horizontal tube of length L, connecting those tubes containing an ideal liquid. Now the free surfaces in both the vertical tubes will be at the same height and will have pressure...
  3. Logic hunter

    Contradicting values of pressure for liquid cross-sections

    Consider a fixed horizontal tube of uniform cross section with pressure being 1atm at one of it's end and 5atm at the other (former due to 'open to atmosphere' and latter due to force on a piston), then liquid would flow towards low pressure end. By equation of continuity all cross sections will...
  4. Logic hunter

    B Direction of buoyant force on sunken object?

    We say that buyont force act upwards (in usual cases) and that the normal force exerted by the base of a container (of liquid) on a object is less than its true weight, so a weghing machine will give smaller reading (in terms of value) than expected. But suppose a cube sinks in water. Now water...
  5. J

    Pressure & Boiling: Exploring Relationship & My Understanding

    Hi everyone, I have been mulling over the relationship between pressure and boiling for some time, and I am still slightly confused. I shall attempt to provide an overview of my current understanding in the hope that I can get some corrections/clarification on my current conceptual...
  6. V

    What is the liquid used to break stone slabs?

    Hi guys, I have seen in my village that there is one guy who is heating up the stone slab for few mins with gas cylinder fire and after few mins. he pouring some liquid on that heated part. Immediately that part becomes break small pieces. He removes them and again heating up and pouring that...
  7. YoungPhysicist

    B Can liquid helium conduct heat infinitely fast?

    Can liquid helium is superfluidity state conduct heat infinitely fast? I thought I have seen this is a paper somewhere a long time ago, but now I am not sure about that.
  8. diegzumillo

    Stargazing Possibility of small bodies of liquid etc

    I'm a physicist but my field is at the other side of the spectrum, but my curiosity has no bounds :P Based on observations we know of several configurations 'clumps of matter' can take, like planets, gas giants, comets, or basic rocks etc. But I always wondered about more unusual possibilities...
  9. M

    The refractive index of an unknown liquid

    1. A light ray in dense flint glass that has an index of refraction of 1.655 is incident to the glass surface. An UNKNOWN liquid condenses on the glass's surface. Total internal reflection on the glass-liquid interface occurs for a minimum angle of incidence on the glass-liquid interface at...
  10. J

    Can liquid ammonia NH3 be electrolyzed?

    Can liquid ammonia NH3 be electolyzed to produce H2 and N2? I have heard of ammonia cracking using high temperature and a catalyst but I was wondering if electrolysis would be an easier way to produce hydrogen from ammonia. The H2 could be fed into a PEM fuel cell to produce electricity to run...
  11. A

    What do surface tension vectors mean in this quote?

    I was reading Fundamentals of Inket Printing and it said the following: "The surface tension in a liquid causes a force to act in the plane of the free surface perpendicularly to a free edge in that surface." Can someone explain to me what this means? What's the direction of the force? I have...
  12. DracoMalfoy

    Thermal physics phase change: Liquid copper to solid

    Homework Statement How much energy must be removed from the system to turn liquid copper of mass 1.5kg at 1083 degrees celsius to solid copper at 1000 degrees celsius? a. -2.49X10^5J b. -3.67X10^4J c. 2.25X10^3J d. 9.45X10^4J e. -2.78X10^3J Homework Equations Q=Mc(Tf-Ti)...
  13. Eagle9

    I Can a liquid or solid plasma exist?

    Excuse me if this is naive question :oldsmile: Plasma is gas where all atoms are ionized. I would like to know if liquid or solid plasma can exist. Let’s take chemical element Lithium, its atom has got 3 electrons and Lithium’s crystal lattice is arranged like this...
  14. O

    Liquid temperature increases when flowing through a 100% efficient pump?

    Hi, For an ideal Rankine cycle, the temperature-specific entropy diagram can be given as follows, The pump in this cycle is isentropically 100% efficient. My question is that why the temperature of the water increases as it flows through the pump (point 1 to 2) if the pump is 100%...
  15. A

    Excess Heat Generated By a Liquid Ring Pump

    Hi all. First, some context. I work for a small seed oil extraction plant where we cold press the seed then solvent extract the residual oil from the presscake. In the solvent extraction plant we use liquid ring pumps to pull the required vacuums. The Plant Vac Pump (PVP) is used in all...
  16. S

    Schools PhD in Liquid Crystal Physics (or Engineering)

    Dear Forum member, I want to pursue research in Liquid Crystal Physics / Engineering, are you aware of any laboratories or university departments actively researching in this field in Canada or Germany? I will be very if you are aware of active groups and share their names. Thanks
  17. Death eater

    Why the specific heat of solids and liquid does not change?

    Why specific heat of solids and liquids doesn't change with change in temperature?
  18. L

    Why do bubbles of air in water move up?

    What I am confused about is why do bubbles of air in water move up. I understand why solids and liquids would move up in water if they are less dense. I get the idea that the deeper you go in water the more pressure there is because of the more water weighing down on the water and so there would...
  19. I

    A five-liter pot is filled with 2 l of liquid water and 3 l of dry air....

    Homework Statement A five-liter pot is filled with 2 l of liquid water and 3 l of dry air at the ambient pressure of 1 atm and temperature 10◦C. Subsequently, the pot is closed and heated up. What is the pressure inside the pot going to be when the temperature reaches 100◦C? Homework...
  20. Z

    Carbon dioxide in liquid and gaseous phases with liquid water

    What are the differences between carbon dioxide solubility (miscibility, reaction) in liquid water when in gaseous (<38 bar) and liquid (>38 bar) phase? The temperature in my experiments is usually between 0 and 5°C. The stirring speed is around 500 rpm. Is the solubility given apart from...
  21. T

    A heat exchanger is to be used to heat a process liquid with....

    Homework Statement (c) A heat exchanger is to be used to heat a process liquid within the tubes using saturated steam at 100oC. The tubes have an inside diameter of 20 mm and outside diameter of 22 mm. It is estimated that the inner surface heat transfer coefficient will be 4.2 kW m-2 K-1 and...
  22. T

    Liquid ammonia is heated as it flows at a mean velocity of 2

    Homework Statement I've completed this problem and received the below feedback but have gone to a state of complete loss on what to do to amend. Can anyone provide a prompt ? Heat transfer coefficient is correct. But heat transfer rate is wrong - the question says Heat transfer per UNIT...
  23. torukojin

    A question about liquid pressere

    1. please help me with the following two questions and explain it to me like I am a 15 years old dummy, thanks in advance
  24. F

    I Liquid water reservoir reported under Mars polar cap

    The analysis is based on 29 radar profiles collected between May 2012 and December 2015. The identified region is about 20-km wide. The report acknowledges the results are consistent with with water or water-laden sediments. A brief discussion on the BBC (with no citations) asserted that...
  25. Edemardil

    Force exertion by liquid in a jar

    c) With what force must a determined 10e-10 kg bacterium cling to the rim? Homework Equations (a) (1rev/2.199m)(50.0m/s)(60s/min) to get w =1364 rev/min (b) Ca = V^2/r = 50.0^2/r I got the radius from 0.700*0.5 = 0.350 2500*0.350 = 7142.86 (c) F = m*a The Attempt at a Solution [/B] (c) I...
  26. M

    Thermodynamics question: venting a tank of liquid oxygen

    I am trying to figure out how you can subcool a dewar of liquid oxygen (vacuum insulated) just by releasing the pressure sitting on top of it. The liquid I am thinking of in this case is liquid oxygen, which boils at -297.33 F at 1 atm. Let's say I fill a dewar with LO2, then pressurize that...
  27. Roy S Ramirez

    Injector pressure drop in a liquid rocket engine

    Hello everybody, I hope you are doing fine. I'm currently designing an injector for a hydrogen peroxide - ethanol engine, and the following formula is confusing me: Q = Cd * A * sqrt( 2 * dP / rho); where Cd is the discharge coefficient, A the total area, dP the pressure drop, and rho the...
  28. A

    Discharge of a Pressure Vessel Containing Liquid Nitrous Oxide

    Homework Statement I want to design a closed tank with an orifice hole (that can be opened and closed remotely) at the bottom of the tank and model how the mass flow rate of liquid nitrous oxide changes with respect to time, as the liquid nitrous oxide leaves the tank due to a pressure...
  29. I

    The acceleration of a bubble in water

    Hi, I have a question about a rising bubble. I read that the initial acceleration of a bubble (with negligible mass) in water is 2g, where g is the gravitational acceleration. I understand that if a bubble rise then the water move around it, but I can't derive this equation. Could someone help...
  30. V

    Flow Rate of Liquid O2 Cylinder w/ 24 Bar Pressure

    Hi. Just looking for an average answer to a practical scenario. At work we use a liquid O2 cylinder which includes an outer jacket that houses a regulated gas pressure of 24 bar. I need to calculate the flow rate in l/min when the supply tap (15mm diameter) is open fully? This is essentially...
  31. dromeascr

    What is the pressure surrounding a liquid at its boiling point?

    Hello everyone, before I start I just want to mention that I am not an expert in physics whatsoever, so please be as specific as you can get if you wish to provide an answer. (The question itself might be considered stupid to be honest) I read the definition of the boiling point recently and...
  32. G

    I Liquid metal slip/rotary contact

    are there any already existing devices on the market or possible ways in which one can make a liquid metal slip contact like a mercury contact in which the mercury can be held at a specific location within a confined space with the help of magnetic field? I know that mercury itself is very weak...
  33. N

    Will the liquid flow split evenly at a T-junction?

    Hi ! I need help on the following problem : I've got a liquid in a pipe that splits into 2 in a "T-junction" (see drawing below) : I want to know if the liquid will split equitably (50% to the left and 50% to the right) or not. Length after the elbow = 3m Inner Diameter 0,27 m Flow volume...
  34. S

    Refraction: object disappearing in liquid

    Homework Statement Why does an object disappear when it is placed in a liquid of refractive index equal to or greater than that of the object? Homework EquationsThe Attempt at a Solution Well, I was just baffled by the problem. Finally, i came up with an answer: we see objects when they...
  35. C

    What is the combustion efficiency of liquid fuel rockets?

    How efficiently is the fuel burned in a typical liquid fuel rocket engine? I've heard numbers ranging from 95% to below 50%.
  36. doctor_cat

    Electrical conductivity of liquid argon

    Dear friends, does anyone know if there exists any study about electrical conductivity of liquid argon? Thank you in advance for any suggestion.
  37. R

    MHB Calculating real world Liquid gas values

    Hello, I am trying to calculate the price of Liquid Gas of 1 TCF - My researce revealed to me that: 1 - I know that 100 cubic feet (Ccf) of natural gas equals 103,700 Btu or 1.037 therms 2 - I know that price per MMBtu multiplied by 1.037 equals price per Mcf 3 - The price of one MMBtu is...
  38. O

    Increasing enthelpy of a liquid

    Hi, I am not sure if this is the correct place to ask this question. When a fluid's pressure gets increased using a pump, does its enthalpy increase too? Thank you in advance.
  39. W

    Advice on making a liquid crystal screen (shutter)

    I need to make my own smart film for some experiments. I've read enough articles on it to know the required components, how they are mixed and applied. I have a 1:1 mixture of liquid crystal and UV curable resin and glass bead spacers that I need to apply between two ITO PETs and UV cure to...
  40. NimzCr7

    Rising of a liquid during rotataion in a cylinder

    Homework Statement [/B] A 25-cm-diameter, 100-cm-high cylindrical container, (as shown), is partially filled with 75-cm-high liquid (density = 900 kg/m3). Determine the rotational speed at which the liquid will start spilling. Calculate the gauge pressure at the centre of the bottom of the tank...
  41. Richie Smash

    Why does conducting liquid moving in a loop produce DC

    Hi suppose you have a conducting liquid in a strong magnetic field, and this is pumped in a continuous loop through two electrodes, why does this produce a D.C current? My thinking is a simple answer, and that is that the D.C current is produce because the fluid is moving in one direction...
  42. Richie Smash

    Find the temperature of Liquid A after 12 minutes

    Homework Statement A liquid A initially at temperature T1= 28.4°C, is heated by an immersion heater in container. The resulting temperature T2 is recorded at 1 minute intervals and the following results obtained. (I will post a picture) (a) Complete the table by computing temperature changes...
  43. M

    Liquid volume loss during pressure test

    Hi, I'm doing a pressure test with a liquid medium. I have a fixed volume and I know the pressure drop, and temperature change - how do I calculate volume of liquid lost in a leak?
  44. J

    Satellite and length of liquid column in a barometer

    Homework Statement Homework EquationsThe Attempt at a Solution Mercury will be in a state of weightlessness in the satellite . The air pressure pushes down on the mercury in the cup as a result of which it rises in the barometer tube . But since it is apparently weightless , it tries to...
  45. S

    Calculating the Torque to mix a liquid

    There is a tank that is 12' 2" long and 65" in diameter that is capable of holding 2000 gallons of liquid asphalt, which is calculated to be 8lbs per gallon, viscosity is 8000CP. There are 8 paddles in this tank that they want to rotate around 25rpm. The diameter of the paddle arms is 60"...
  46. R

    I Matter density on the bottom of a liquid container vs hanging in the middle of it

    Why is the rough diamond in the following video held by a wire from above? Is it just so it will be easy to take the rock out of the water glass or is it to prevent the diamond from sinking to the bottom? If it is to prevent the diamond from sinking to the bottom, what is the reason for that ...
  47. wolram

    B New Topographic Map of Saturn's Moon Titan Reveals Liquid Flows

    Using the now-complete Cassini data set, astronomers have created a new global topographic map of Saturn's moon Titan that has opened new windows into understanding its liquid flows and terrain. https://www.sciencedaily.com/releases/2018/01/180106190439.htm I found this fascinating I hope others do.
  48. S

    I Why is Liquid Neon Not Typically Used in Bubble Chamber Detectors?

    Is liquid neon popular for bubble chamber detectors?
  49. S

    Liquid crystals: dielectric torque and electric torque

    Dear Members, I was reading a tutorial on ferroelectricity of liquid crystals, underneath is the excrept: "For ferroelectric materials, in addition to the dielectric torque, the electric torque will have a term due to the linear coupling between the spontaneous polarization" Could someone...
  50. B

    I Hydrogen plasma compression with liquid Mercury piston

    I'm working on a thought experiment. I want to know how much of the kinetic energy from a liquid mercury piston will be converted into work done on the hydrogen plasma in the form of compression, and how much work will be done on the piston in the form of compression. Note: assume piston walls...
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