Chemical Definition and 1000 Threads

A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be simple substances, chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, table salt (sodium chloride) and refined sugar (sucrose). However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.
Chemical substances exist as solids, liquids, gases, or plasma, and may change between these phases of matter with changes in temperature or pressure and time. Chemical substances may be combined or converted to others by means of chemical reactions.
Forms of energy, such as light and heat, are not matter, and are thus not "substances" in this regard.

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  1. askingask

    B Would it be feasible to make a chemical inertial confinement reactor?

    So basically, instead of using large complex pumped lasers, we use chemical lasers that have insane power output. They are used to fuse a fusion pellet. The excess energy is collected and part of it is used to prepare the next batch of chemicals needed to run the laser. What would be the...
  2. S

    Looking for a chemical with a boiling point between 10C and 50C

    i am looking for a chemical compound that has a boiling or condensation temperature between 10C and 50C at standard pressure and is not one prohibited for discussion in the Physics Forum or any online chemical forums. something that is organic and not very toxic is preferred. it should be...
  3. J

    Chemist unwillingly turned chemical engineer

    Hello, I'm just out of grad school working now as a chemical engineer, though the problems I've been asked to solve are quite varied in nature. I've known about and have used physics forums for a while, and just got around to making an account. I hope to learn a lot from here.
  4. C

    ChemE Major

    Hello! I am currently a chemical engineering major. I love all of my class but I am struggling in Physics
  5. Gstoettenmayr

    How Can a Multidisciplinary Engineer Advance Fertilizer Production Techniques?

    Hi there, Thank you for welcoming into your community. I completed a five year electrical control engineering college, then studied chemical engineering followed by a PhD in analytical chemistry. Since the last seven years I work in a role that involves chemical engineering and process...
  6. C

    What Happens to Blue Sphere Silica Gel at High Temperatures?

    What type of chemical and physical transformation occurs in the blue sphere silica gel when it is subjected to very high temperatures above the temperature supported by it for several minutes? does it turn into a compound that will absorb and store moisture and water inside and can leak if it...
  7. D

    Search for specific near infrared transparent materials

    Hello everyone, I am looking for a material with the following characteristics: - It must be machinable - be as thermally insulating as possible, and resistant to a temperature of at least 100°C - transparent to near-infrared light (~1µm wavelength) - relatively resistant to deformation, for...
  8. S

    Hexagon Patterns in Chemical/Molecular Makeup

    Are physical atoms really arranged in hexagon patterns, or is that some sort of way to represent them for illustrations in textbooks and in science articles? (i.e. atoms aren't actually arranged in any hexagon pattern)
  9. C

    Need a surface mount seal for chemical cabinet door

    I want to build a mini chemical cabinet to try to eliminate odors in my garage as my wife thinks the car interior now smells. The chemical resistant rubber strip sealant is crazy expensive, but as the intended use will just be fumes with no actual chemical or fuel contact to the seals, can I use...
  10. nur20

    What is the chemical name for C9H20O9Cl ?

    I am trying to find out it's name.Please help me
  11. G

    Calculating Chemical Potential from Energy Derivatives

    Hi Unfortunately, I can't get on with the following task. The system looks like this it is divided in such a way that the same number of particles is present in each ##\epsilon## section. I am now to determine the energy ##E(P_h,V_h,N)## at the height h using the energy ##h=0## i.e...
  12. Mayhem

    Resources for IR tables for inorganic chemical bonds

    I recently had to do some IR specs of some inorganic compounds (technically organometallic), and I found the literature for inorganic bonds lacking, like the wavenumber of metal-oxygen, metal-carbon bonds etc. Is there a data book on this?
  13. samy4408

    A question about chemical equilibrium

    Hello we learned about the chemical equilibrium and how to write it's formula in the case of liquid and gaseous phase , what about a reaction involving different phases ? like this one : how do we write the formula for the chemical equilibrium ? do we just ignore the carbon ,is there any rules...
  14. samy4408

    Chemistry An exercise about chemical equilibrium

    Hello i am trying to solve a problem set about chemical equilibrium , the issue is that my results don't correspond to the correction . can someone tell me what is wrong with my answer , thanks here is the problem and his correction : here is my answer :
  15. samy4408

    Chemistry Confused by an exercise on the subject of chemical equilibrium

    Hello , i am a little confused about this exercise because we talk about gases reaction and we are asked about the concentrations P.S : i have other questions that depends on your answer . Thanks .
  16. B

    How to test for a purity of a chemical compound

    If you had this chemical compound, for example, how could you test if its pure? $$C_{15}H_{11}I_4NO_4$$
  17. G

    Biology Chemical compounds that I can visualise

    I am actually studying engineering but we are making a project about chemistry, and i don`t know much about it. I need chemical compounds that i can visualise. For example water. need help [Thread moved from the technical forums to the schoolwork forums by the Mentors] [...and thread contents...
  18. A

    Chemical plant design and construction

    Got some good resources on Chemical plant design and construction. A Chemical plant design and construction. B Chemical plant design and construction.
  19. D

    Trying to source a chemical product

    Freezable. Maintains flexibility when frozen. Re-usable. Non toxic. Need to know the chemical name to enable sourcing for a manufacturer.
  20. barryj

    Using matrices to balance chemical equations

    I am working with matrices to balance chem equations. I have googled hard equations to balance and find that most, at least what I have found, have the number of elements to be less than the terms in the equation. for example ... FeCr2O4 + ... Na2CO3 + ... O2 -->... Na2CrO4 + ...Fe2O3 + 1CO...
  21. A

    Balancing Chemical Equations - Is RHS=LHS true always?

    Below are some examples of Chemical Reactions/Equations. 2H2 + O2 = 2H2O CU+ H2SO4=CUSO4 + H2 2MG + O2 =2MGO 2NA + CL2 =2NACL and so on ... I mean is RHS=LHS always true for all Chemical Equations or only for specific chemical equations or not true at all? 2H2O=2H2 + O2 CUSO4+H2=CU+H2SO4...
  22. L

    Can any type of refrigerator work without a chemical refrigerant?

    I was just wondering if a mini fridge could ever work on electricity alone with no toxic chemicals inside?
  23. S

    Is electrolyte chemical consumed during alkaline water electrolysis?

    In alkaline water electrolysis you add Potassium hydroxide, or Sodium hydroxide to the water you want to turn into hydrogen and oksygen. But is the Potassium hydroxide, or Sodium hydroxide consumed during electrolysis and needs to be replaced? Or do you just have to keep adding water as it is...
  24. D

    Chemistry Chemical Equilibrium: find concentration from 2 solutions (ICE table)

    Hello! I've recently encountered this problem https://www.physicsforums.com/threads/need-major-help.117630/ and solved it and I'm stuck at choosing between 2 solutions. I don't understand why do we need to plug in 0.39 and 0.65 to (1-2x) and NOT to (1-2x)^2. I mean, we were given 2NO2, not just...
  25. chikchok

    I Chemical potential and Fermi level

    Does fermi level (in metals) depend on the density of states? I am asking this because from fermi-dirac distribution it seems like that fermi level is non-dependent of DOS, but there is chemical potential in fermi-dirac distribution, which is said to be dependent of DOS.
  26. Yash Agrawal

    Thermodynamics of chemical reactions

    In chemical reactions generally ΔG < 0 , but if we were to consider a reversible path between pure reactants and products at 1 bar pressure , shouldn't the ΔG = 0 for every reaction ? and if it is due to non-pv work , I don't see any non pv work being done in reactions happing in a closed...
  27. Mayhem

    Chemical inhibitions of radioactive elements

    Is it possible to chemically inhibit (block/absorb) ionizing radiation from radioactive elements, and is any research being done in this area to use it for long term storage of nuclear waste (in conjunction with other precautions, of course)?
  28. Ale_Rodo

    What's the derivation of the 'Kinetic Equation' in Chemical kinetics?

    Hi, I'm following an introduction course to chemistry and I am reviewing the chapter on Chemical kinetics. It's shown that the reaction speed for a certain component of a general chemical equation such as aA +bB <-> cC + dD , might be expressed as v = k[A]m[ B]m. I was wondering where it does...
  29. SilverSoldier

    Approximations in Chemical Equilibrium (add a weak acid HA into pure water)

    Suppose we add a weak acid HA into pure water, so that upon addition its initial concentration is c. The following equilibria should establish in the system. $$\text{HA}+\text{H}_2\text{O}\rightleftharpoons\text{H}_3\text{O}^++\text{A}^-$$...
  30. W

    Controlled chemical pressurization formula

    I have spent years physically charging high pressure bottles with multi staged bicycle pumps and spent large sums of money on electric high pressure air pumps not unlike a scuba tank air compressor. Pressure’s can be as high as 4500 PSI . The pressurized bottles are usually 300 to 500 cc’s. I...
  31. C

    Ant chemical trails and detectors Moved to Biology

    1. How do you remove ants chemical trails on the wall? Water and rug not enough? 2. What are the exact details of the ants incredible chemical sensors in their antenna? How can they able to tell the difference between a hydrocarbon with 25 carbon atoms versus 24 atoms? 3. Lastly, is there an...
  32. J

    Chemistry Expanding and Naming of Abbreviated Chemical Formulas

    I noted that the number of carbons in the main chain is 7 (5 carcons and the outer two are attached to an outside 'CH3' grouping .. and the bonds are all single so we have a Heptane. We have the main chain diagram structure as follows .. -C-C-C-C-C-C-C- .. If we then number these carbons...
  33. Kaguro

    Chemical potential and fugacity

    I am trying to learn statistical physics. While learning MB statistics, my textbook defined chemical potential as ##\mu = (\frac{\partial F}{\partial N})_{V,T}##. That's nice. Later when I started on Quantum statistics, my textbook described all three distribution functions via: ##n_i =...
  34. Will26040

    How do I get the viscosity of a mash mixture in brewing?

    Hi, I am designing a mash tun to produce beer. I have 1300kg of malted barley (at a known density) and 3250kg of water. Please could someone outline a method I could use as I am really struggling. One of the main problems I am having is accounting for the density change of the malt when it...
  35. K

    Does an RFID wallet contain any chemical addictives?

    Does RFID wallet or any other wallet that suggest to be protecting contain any chemical addictive or have a different composition of material so that they can protect against unauthorized card reading?
  36. S

    Can we write mass in coefficients of elements in a chemical equation

    let's take a chemical equation - CH4+2O2 ------> CO2+2H2O From Reactant side- the coefficient of CH4 is 1 and the coefficient of O2 is 2 From Product side - the coefficient of CO2 is 1 and the coefficient of H2O is 2 we can write this chemical equation in terms of molecules,atoms,moles. Can we...
  37. B

    Solving Chemical Equilibrium Concentrations Within a Rocket Nozzle

    I would like to write a program to calculate the equilibrium concentrations of 10 or more chemical species at any axial location along a quasi 1D isentropic methane-liquid oxygen rocket nozzle. Is anyone aware of any good textbooks that cover this topic in depth, specifically dealing with large...
  38. J

    Thermodynamics problem relating to Chemical Potentials

    For part (a), I used this formula where where the i's represent the substance being used and mu_i^0 represents some reference potential. However, to my knowledge this simply calculates the change in chemical potential from one state to another which is not of much help in finding the relative...
  39. Will26040

    Solving Slurry Bed Adsorption: Calculating Residence Time & Isotherm Selection

    Summary:: I have an assignment on slurry bed adsorption and would like to know how to calculate residence time as it is not specified. I was also wondering if anyone had any suggestions for another isotherm to try and fit the data to (other than freundlich). Thanks ##\frac {dq} {dt} = \frac...
  40. jkmiller

    What Chemical Properties Affect Young's Modulus?

    I can't seem to figure out which chemical properties govern the physical property that is young's modulus. For example, any linear (or with a low degree of branching) polyethylene with no crosslinking is still a somewhat rigid and solid substance (higher ym), whereas the most linear possible...
  41. K

    Could electrical part react with chemical?

    I have need to put some chemicals INSIDE a home electrical appliance which is a closed area. I am thinking and worried that if electrical parts could react with chemical and cause problems? The only possibility I can think of is if the spark from electrical appliances could react with...
  42. P

    Why does roofing occur despite the difference in chemical shift?

    J is 7.2 and 7.1 for the triplets (7.2 for the pentet, 7.1 for the sextet), chemical shift 0.93 and 2.62Also is it a AMSX or AMX spinsystem?
  43. E

    Meaning of small triangle in chemical potential

    It is given that the solution is ideal, i.e. that we can take ##\gamma_A = 1##. I wondered what that small triangle signifies in the second definition? Thanks!
  44. Adrian Tudini

    Energy level diagram of a chemical reaction

    Hi For a personal project, has the energy level diagram of the below reaction been derived? Voltage Applied4B+2LiNO3+C ------------->B4C+2LiNO2+O2 Thanks,
  45. Kiah Palmer

    Chemistry Mass of an element required for a chemical reaction equation

    Conversion: 9.65 kg = 9650 g Mass Al = 26.98 g/mol Molar Mass Al2O3 = (2 x 26.98) + ( 3 x 16.00) = 101.96 g/mol Mol Al2O3 = 9650 g / 101.96 g/mol = 94.65 mol Mol Al Required = 94.65 mol x 2 = 189.3 mol Mass 100% Al required = 189.3 mol x 26.98 g/mol = 5.107x103 g Mass 80% Al required =...
  46. WMDhamnekar

    LaTeX Drawing Lewis Diagrams & Chemical Equations with LaTeX

    Hi, How to draw Lewis diagrams, Lewis symbols , chemical equations in LaTeX?
  47. Kiah Palmer

    Chemistry Homework Help: Calculating Mass from Chemical Reaction Equations

    1a) Step 1: Balance the equation - S8 + O2 -> SO2 = S8 + 8O2 -> 8SO2 Conversion (t to g) 6.00 t = 6x10^6 g Molar mass SO2 = 23 + (2 x 16) = 64 g/mol 6x10^6 g / 64 g/mol = 9.375x10^4 mol SO2 reqired amount Sulphur = 9.375x10^4 mol / 8 mol = 1.172x10^4 mol S8 Molar mass S8 = (8 x 32)...
  48. M

    Is this a more accurate representation of a molecule?

    I see the top version used everywhere. But isn't the bottom version better? Because the top version makes it seem like H2 bonds with the C to its right and the other H2 bonds with the N. Whereas the bottom version shows the bonds correctly. Should I draw it like the top version and stop annoying...
  49. jaumzaum

    What chemical properties affect the specific heat?

    Hello all! I would like to know what chemical/physical properties influencies the specific heat. For example, why are specific heat of metals smaller than the specific heat of water, and why do ice and steam have a smaller specific heat than liquid water do.
  50. A

    Chemical reactions to depict Le Chatelier's Principle (Temperature)

    If an endothermic reaction has a lower temperature, since the forward reaction rate decreases more, the reaction should produce more energy to compensate for the decreased energy and raise the rate of the forward reaction until it reaches equilibrium with the reverse reaction. Is this saying...
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