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. O

    Is an Ionic Bond Not a True Chemical Bond?

    In a 2003 post about electrons and their behavior, which as a rule goes, tended not to get to a final solution, there was a quote by a poster: "There is no chemical bond between chlorine and sodium. That is to say it is only electrostatic attraction, an ionic bond as opposed to a covalent bond...
  2. P

    How Would You Precipitate BaCrO4 from Ba(NO3)2 and K2Cr2O7 Solutions?

    Homework Statement Hi everyone, I'm trying to finish my lab report but I'm stuck on this question and don't even know how to start it. Could anyone let me know how to board it or a starting clue? I'm given these two equations 1. BaCrO4 (s) <---> Ba2+ (aq) + CrO42- (aq) 2. 2CrO42-...
  3. Y

    Need suggestion of commercial chemical to clean shower stall

    Hi I have a hard time cleaning the deposit on the floor of the shower stall made of Dupont Corian. I believe it's a combination of hard water ( known to have hard water), soap scum. I tried scrubbing with all different household stuffs including Soft Scrub, Tilex and other common stuffs with...
  4. W

    Engineering Transfer to chemical engineering from BS in chemistry?

    Hi. I'm currently an undergraduate student studying for a BS in chemistry and doing pre-pharm courses (I wanted backup career). I've taken anatomy and orgo lectures and labs. What I enjoy from orgo class was that they give you a start and an end, you fill in the rest. I like problems that are...
  5. K

    Chemical Equilibrium and Le Chatelier's Principle

    Homework Statement Without adding any Chromium based compounds, how would you manipulate the above equation to produce more CrO42- ions? Be sure to use chemical equations to show the answer. Homework Equations 2CrO42- (aq) + 2H3O+ <--> Cr2O72-(aq) + 3H2O (l) The Attempt at a Solution So my...
  6. Suraj M

    Synapse: chemical vs electrical

    electric transmission between 2 neurons is way faster than by chemical neurotransmitters... then why are there so few electric transmission based synapses in our body??
  7. S

    Books on Atomic Structure, Chemical Bonding, Quantum for Beginners

    Hi all! I would like to ask your help! I am a rookie in the subject. I have to admit i don't exactly interested in the mathematical way. I really don't have the "basic" advanced math which would needed it. :) Look at me if i would be a high school physics and chemistry teacher whose imaginary...
  8. T

    Chemical Formulas: Interpreting Single Atom Reactions

    This is a very basic question. When I see a chemical formula, like for example combustion of methane: $CH_4+2O_2->CO_2+2H_20$ and I compute the standard enthalpy of reaction $H_r$, do I have always to think about this value $H$ and about the chemical reaction as describing a "certain amount"...
  9. G

    Prove Conservation Laws Prevent H+H->H2 Reaction

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  10. S

    Kinetic equilibrium of chemical reaction

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  11. S

    Does Copper's Oxidation State Need Specification in Chemical Reactions?

    Homework Statement A student performs a single replacement reaction by dipping a strip of copper metal, Cu(s), into an aqueous solution of silver nitrate, AgN03(aq), to produce silver, Ag(s). Write the balanced equation. Homework Equations The Attempt at a Solution The answer has...
  12. L

    Thermodynamics: ideal gas chemical potential

    Can someone explain me why we could put pi, μi and μiο in this equation: and we get this: (this is The chemical potential of a component in a perfect mixture of ideal gases wher pi is partial pressure)
  13. EhtYlno

    Engineering Electronic Engineering vs Chemical Engineering

    Right now I have a choice between these two disciplines, Chemical or Electronic engineering. Which one would remain suitable for me? My friends advice me to get into Chemical Engineering since they say its in a huge demand right now, however I am more inclined towards Electronic Engineering...
  14. N

    What Causes Magnetism and Repulsion in Magnets?

    When you take two magnets one being positive, the other negative. What is the chemical makeup of these two magnets that makes them repel each other. And if I have this correct, electricity is caused by magnet coils spinning around which generates electricity. What is it about magnets (especially...
  15. avito009

    How does the balanced chemical equation tell us the state?

    How does the balanced chemical equation tell us the products are in which state? Solid, Liquid, or Gas or aqueous?
  16. sunshine1025

    Food Chemist vs. Chemical Engineer- Help

    First, thank you for taking the time to read this. I need some guidance as I am inventing somewhat of a new edible product. Curious as to if someone can point me in the right direction for the type of chemist I should actually be looking for. At first I was under the impression that it would be...
  17. H

    AP Chemistry Chemical Kinetics Problem

    Homework Statement The rate of the reaction was studied at a certain temperature. O(g) + NO2(g) --> NO(g) + O2(g) In the first set of experiments, NO2 was in large excess, at a concentration of 1.0 * 10^ 13 molecules/cm3 with the following data collected. time (s) [O] (atoms/cm3) 0...
  18. Avatrin

    Book on Chemical Thermodynamics

    Hi I am currently using a book called "An Introduction to Thermal Physics" by Daniel Schroeder, and there is a part of the book I am struggling with. So, I am looking for some other book that can help me learn the same stuff (to get a different perspective on the same material). For people...
  19. Y

    How are bubbles removed in a chemical reaction?

    Hi all, I am really confused at how bubbles are removed in a chemical reaction. Generally it is removed by diffusion...But is there any quantitative equation for that like adhesion energy...? I want to go in this direction to quantitatively analyse the conditions that bubbles are attached or...
  20. T

    Chemical engineering first year student

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  21. S

    What defines density of chemical substances?

    What defines density of chemical substances at the same pressure and temperature?
  22. D

    How Do You Find Internal Energy with Chemical Potential?

    Homework Statement Given dE=TdS-PdV+\mu dN, PV=NT and Cv=\frac{3}{2}N Find E Homework Equations dE=TdS-PdV+\mu dN, PV=NT and Cv=\frac{3}{2}N The Attempt at a Solution That part that is confusing me is the chemical potential, not sure what to do with it. Finding the energy for the ideal...
  23. T

    Medical Help Tess Neutralize Chemical Reaction Fumes in Her Home

    Hi, I wonder if you guys could help me. During the summer I used a mould spray on upvc windows which contained anionic surfactants with chlorine bleaching agents. I rinsed this off but it left a white film on the glass and so I used a household cleaner called Flash which has < 5 % Non-ionic...
  24. 1

    How Do You Balance Complex Chemical Equations in Ionic and Neutral Forms?

    Homework Statement Write the balanced chemical reactions in ionic and neutral forms for: i) Enargite leaching by sodium bisulfide in basic solution to form chalcocite and thioarsenate. ii) Oxygen pressure oxidation of As2S5 in acid solution to form scorodite. Assume all sulfide sulfur forms...
  25. J

    Physical Chemistry: Chemical Equlibrium

    Homework Statement For the reaction: 2SO3(g) →2SO2(g)+O2(g) when 2.00 mol of SO3 is added to a flask at 10.0 L and 350 K at fixed volume, at equilibrium the ratio of SO2:SO3 is 0.663. What is the values of the equilibrium constant? What is ΔG° at this temperature? Homework Equations...
  26. B

    How is Chemical Potential Affected by Altitude in an Ideal Gas?

    Homework Statement Consider a monatomic ideal gas that lives at a height z above sea level, so each molecule has potential energy mgz in addition to its kinetic energy.(a) Show that the chemical potential is the same as if the gas were at sea level, plus an additional term mgz:μ(z) = -kT ln...
  27. Z

    Engineering Graduate school in Chemical Engineering good for career in industry?

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  28. C

    Why is the chemical potential negligible at equilibrium?

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  29. alpha358

    Thermodynamics: ideal gas chemical potential pressure dependence

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  30. W

    Chemical Engineering and Thermodynamics

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  31. S

    Optimizing Chemical Injection for Viscous Polymer in Winter Conditions

    see attached. the main 10" header is water, and the 1/2" chemical injection is polymer feed (not sure how much by volume, we go by pump strokes). problem is during winter, the polymer becomes viscous, and the pump has a hard time pumping the stuff all the way to the header. So we're thinking...
  32. S

    Charging objects by friction & chemical reaction

    While rubbing the plastic rod with the wool causes the building up of charges on both of them. 1. What chemical reaction takes place between them. 2. Does it create anions and cations? 3. Is it the transfer of free electrons (I don't think so, because generally they are bad conductor of...
  33. S

    Triboelectric effect and chemical reaction

    Homework Statement While rubbing the plastic rod with the wool causes the building up of charges on both of them. What chemical reaction takes place between them. Does it create anions and cations? Does it create free electrons (I don't think so, because generally they are bad...
  34. S

    Chemical that reacts with glass and cools

    Hi, I'm far from a chemist / engineer but am looking for something that will react with glass and cool to around 40 deg F. Any ideas?
  35. F

    Can a Graph of Concentration vs. Time Reveal a Balanced Chemical Equation?

    Homework Statement I'm just rewording the question, because there is one thing in particular I'm after. Given a graph of A, B, & C in Concentration(y) versus time(x), can you determine the balanced chemical equation? Is that possible? I guess if you found the rates and then checked to see...
  36. F

    Solve 2nd Order Reaction Kinetics: Mn(CO)sub5 → Mnsub2 (CO)sub10

    Homework Statement The second order reaction 2Mn(CO)sub5 → Mnsub2 (CO)sub10 has a rate constant equal to 3.0 *10^9 M^-1s^-1 at 25oC. If the initial concentration for Mn(CO)sub5 is 1.0 * 10^-5 M, how long will it take for 90% of the reactant to disappear? Homework Equations Rate Law =...
  37. M

    Chemical engineering problems in metallurgy industry

    Dear mates: I'm looking for a reference of the chemical engineerin problems: heat transfer unit operation, separation unit operation, grind unit operations, reactor operations for metallurgy and material science industry. Please recommendme the best one you know With all the best...
  38. wirefree

    Chemical arithmetics: Answers not matching

    Question: 2.0 g of a mixture of Na2CO3 and NaHCO3 was heated when its weight reduced to 1.876 g. Determine the percentage composition of the mixture. Attempt: Here is my attempt: Problem: My answers do not match those of the text. More critically, the procedure I've adopted is...
  39. Ritzycat

    Going to school for chemical engineering

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  40. S

    Why Do Io and Titan Exhibit Unique Surface Phenomena?

    Hello, first post here. I'm trying to wrap my head around something here and I'm wondering if anyone can help. I've read that all terrestrial planets have basically the same chemical components - Iron, Silicon, Oxygen, etc - in roughly the same percentages. I also read that the composition of...
  41. S

    Should I be a Mechanical Engineer or a Chemical Engineer?

    Hey guys, I'm 16 this year and I've already decided to be an engineer. it's just i don't know what type i want to become. I am leaning towards mechanical engineering more because i heard you get to break things apart and assemble them. and it's the most diverse engineering branch. i...
  42. M

    Develop sensors that detect chemical substances

    hello! is there a degree that studies the interaction between radiation, light, ultrasound, electromagnetic waves, etc with matter? in particular to develop sensors that detect chemical substances thanks!
  43. M

    What is the Chemical Name of SnMg2O4?

    Dear community fellows Can somebody help me in identifying the name of SnMg2O4 ? Other examples are ZnAl2O4 (Zinc Aluminate), ZnIN2S4 (Zn Thioindate). Kindly provide the reference if possible. Thank You Masood
  44. K

    Chemical reaction of electrochemical etching

    Greetings all, I have some questions regarding to chemical reaction between Silicon,Si (wafer) and chemical dissolution. FYI, I'm doing electrochemical ething to fabricate porous Si. Could anyone help me to solve this chemical reactions? 1) Si (silicon wafer) + HF (hydroflouric acid)+...
  45. WannabeNewton

    Surfactant adsorption chemical equilibrium

    Homework Statement A dilute solution of surfactants can be regarded as an ideal three-dimensional gas. As surfactant molecules can reduce their energy by contact with air, a fraction of them migrate to the surface where they can be treated as a two-dimensional ideal gas. Surfactants are...
  46. A

    Crystal Lattice of Spin-1 Particles: Chemical Potential?

    Homework Statement A crystal lattice consists of a spin 1 particle at each lattice point. Spin 1 particles can have z-components of magnetic moment that take on the values +μZ, 0, and -μZ. In an external magnetic field B, each spin can have an energy U = -μZB, so the possible energies are...
  47. Q

    How are chemical bonds described by quantum mechanics?

    I'm currently doing my Bachelor's in Physics(1st year). My textbooks aren't too clear on quantum mechanical concepts. "Bonds are formed by overlapping orbitals". I have several questions. I've seen the graph of potential energy versus distance. For some pairs of atoms like hydrogen it dips at a...
  48. T

    3D Graphene foam from glucose by chemical blowing

    I'm a third year physics undergraduate and I want to make 3D Graphene - without spending a fortune. This is my background: I found this review article by Jiang and Fan (Design of advanced porous graphene materials: from graphene nanomesh to 3D architectures) to be very helpful. From what...
  49. BrainMan

    Pb(MnO4)2: Lead Permanganate Formula

    Homework Statement Write the formula of : lead(2) permanganateHomework Equations The Attempt at a Solution So I know that this formula is the combination of lead magnesium and oxygen. I know that the -ate suffix means that it has the most number of oxygen ions possible. The answer was Pb...
  50. T

    Chemical Engineering and physics?

    Does anyone know if chemical engineering is any interesting? I am only considering engineering majors now because of job prospects. Chemical Engineering I heard has a lot of physics and physical chemistry in it. I would like to go to grad school in physics and do something experimental and I am...
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