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. U

    Chemical potential vs hydro-static pressure during osmosis

    So when osmosis between two solutions (separated by a semipermeable membrane),takes place, the solvent travels from the side where its chemical potential is higher to the side where its chemical potential is lower. However, this results in a difference of levels of fluids across the membrane...
  2. C

    Engineering Material and Chemical Engineering, which to choose?

    Hi everyone, I'm an a-level student (year 13) doing Physics, Chemistry and Maths. I am struggling of what university subject to apply for...I want to do a subject that is a combination of all three subjects I'm now doing. I like topics that I can go very very deep. I think quantum and...
  3. D

    Pursuing a PhD in Chemical Biology?

    When I started college, I was a biotechnology major. I found this major be a dumbed down version of molecular and cellular biology, so I decided I wanted to switch out of it and major in biochemistry and molecular biology focusing in biochemistry, the problem was that I had already taken two...
  4. G

    What happens to atoms that havent reacted in a chemical reaction?

    So let`s say that we have a chemical reaction with liquid oxygen and liquid hydrogen, but we`ve got very little hydrogen, and very much oxygen. As we pour these two liquids together they react with on another and create water. However since there was a very much bigger amount of oxygen than...
  5. K

    Chemical production of ozone in the laboratory

    The followings are the chemical reactions I learned at my university: K2S2O8(s) + H2SO4(concentrated) → H2S2O8 + K2SO4 H2S2O8 + 2H2O → H2O2 + 2H2SO4 H2O2 (heat)→ H2O + [O] [O] + O2 → O3 However, I'm wondering why I can't find these reactions anywhere on the Internet. What do you think...
  6. P

    Calculating Mass from Chemical Reaction

    Homework Statement what is the mass of alum that can be prepared from 1.340g of Al. Homework Equations 2Al+2KOH+4H2SO4+22H2O ---> 3H2 + 2KAl(SO4)2 * 12H2O The Attempt at a Solution given Al is the limiting reagent. Find the moles of Al using n=m/M I find Al moles to be...
  7. K

    Chem Eng: Calculate Heat Req for Temp Change from 25°C to 250°C

    Homework Statement Prior to entering a combustion furnace, air is heated up from ambient temperature (25 °C) to 250 °C. This change in temperature causes the specific enthalpy to change to 3745 J/mol. Assume that the pressure of the air leaving the heater is 150 kPa and the flow rate is 1.3 m3...
  8. V

    Learn Inorganic Compound Nomenclature with IUPAC

    I think one of the most important aspects of learning is knowing how to organize information in your head. And after all this time I realized I don't know the rules behind chemical nomenclature as well as I should; for instance, I can name chemical compounds just 'cause, having no idea why that...
  9. P

    Best chemical companies to work for

    I'm curious if anyone has specific advice or experience. I'm looking for things like benefit to society, interesting work, and skills that extend to other areas. I know chemical engineers can work for most companies in the industries of semiconductor, paper, petroleum, chemical...
  10. A

    How Do You Calculate Percent Yield of C2H5Cl in a Complex Reaction?

    Homework Statement "The reaction of ethane gas (C2H6) with chlorine gas produces C2H5Cl as its main product (along with HCl). In addition, the reaction invariably produces a variety of other minor products, including C2H4Cl2, C2H3Cl3, and others. Naturally, the pro- duction of these minor...
  11. andyrk

    Kossel Lewis Approach To Chemical Bonding

    We know that a shell can accommodate a maximum of 2n2 electrons because a shell can have a maximum of n2 orbitals depending upon the value of n, i.e n=1 for K shell, n=2 for L shell, n=3 for M shell, n=4 for N shell and so on. According to Lewis, he pictured the atom in terms of a positively...
  12. epenguin

    News Syria Chemical Warfare: Analysis & Probabilities

    At this scientific site it should be possible to get some better informed considerations than I am finding elsewhere about the probabilities concerning what has happened in Syria. There appears little doubt that a population has suffered an attack involving probably sarin, and I think...
  13. U

    Did you become a chemical engineer for the money?

    I've posted questions on other forums asking people why they became engineers, and the majority of people claimed they did it because of a passion for building things, interested in how things work, etc. However, when doing a search on this forum, I stumbled upon this thread...
  14. L

    Websites to put an ad to hire a temporary chemical engineer

    I would like to know if you can tell me the name of websites where I can put an ad to recruit a temporary chemical engineer. I am looking for an alcohol technologist who can make the drawings of a small distillery for the production of extra neutral alcohol at 96.2% for beverages. The raw...
  15. N

    Can KNO3 and bentonite clay increase rocket engine performance?

    Question, If I make a rocket engine using KNO3 fuel and bentonite clay for the nozzle, shouldn't the ISP of the engine be slightly higher due to the radiation? It would be nearly Immeasurable but nevertheless there. Kind of like the way a NERVA engine works.
  16. Pythagorean

    Carbonation sensation is a chemical reaction, not physical

    But can be modulated by bubbles. PLOS ONE: The Influence of Bubbles on the Perception Carbonation Bite
  17. C

    Chemical potential and fixed number of particles

    Can we talk about the chemical potential of a system with fixed number of particles? Is this physically meaningful? Why/why not? P.s: I know that chemical potential is the partial derivative of free energy with respect to number of particles. But in the formulation of grand canonical...
  18. jaumzaum

    Substances whose chemical reaction is easily perceptiple

    I was trying to solve the following exercise: Choose the option that has the pair of substances whose chemical reaction is easily perceptiple a)Br2(aq) + NaCl(aq) b) Cl2(aq) + NaI(aq) c) H2(g) + MgSO4(aq) d) Ag(c) + ZnSO4(aq) e) HCl(aq) + Cu(c) I would say if the salt was an alkali...
  19. S

    Can Cymatics Enhance Chemical Production Efficiency?

    Just beeen reading and watching youtube videos about cymatics, and how sound can force sand on a plate to conform to a specific pattern based on frequency of the sound. Now I am no expert in chemical production but from what i can remember, sometimes elements are mixed together in high...
  20. G

    Battery to replace chemical electron donor

    In reactions that reduce organic compounds through donation of electrons, can a battery substitute as an electron donor? In a typical mercury/aluminum amalgam reaction, aluminum donates the electron to the compound that is going to be reduced. The mercury serves as a mediator for the...
  21. K

    Question w/ chemical potential, equivalence to Energy or Potential?

    I have a quick question, is the chemical potential $$\mu=\partial F /\partial N$$ where F is the free energy physically equivalent to a potential or energy? For example, in electrostatics, $$V=U/q$$ Does $$\mu_{ext}= U \text{ or } V$$ Also, same thing could be asked about gravity...
  22. T

    A fatal chemical Reaction for TV Series

    I am currently in the process of re-writing an episode for a Science Fiction television series. I have two problems. A scene at a Japanese Naval Base where I need to inflict mass casualty thru a chemical reaction that will affect only the area of the naval base itself, and wipe out all the...
  23. T

    What Chemical Causes Wood to Change Color in Sunlight?

    Just wondering if anyone might have a guess as to what chemical this could be based on it's apperance when it is applied to wood. I found this picture on a woodworking site. This is some kind of chemical stain for wood. When first applied to wood it is a lemon yellow color but after a few...
  24. L

    The electrical energy produced from chemical reactions

    Hi there, new member here (**TL,DR is available at the bottom of this post**) As you may or may not know, if you were to put in a plate of zinc at one end and a plate of copper at the other, put them in an acid solution, electricity will be produced. More of that stuff here...
  25. Saitama

    Chemical Kintetics - Sequential reactions

    Chemical Kinetics - Sequential reactions Homework Statement For a reaction ##A \rightarrow B \rightarrow C##, ##t_{1/2}## for A and B are 4 and 2 minutes respectively. How much time would be required for the B to reach maximum concentration. Homework Equations The Attempt at a...
  26. M

    Home projects for chemical engineering?

    Hello, I just finished my lower division chemistry/physics sequence, and next semester I am transferring and will start taking my upper division chemical engineering classes. I was wondering what sort of projects I can do at home with my knowledge, or if someone can share ideas for DIY type...
  27. marellasunny

    Chemical equilibrium reaction for burned gases in engine

    I do not understand how equation(3) occurs.(taken from the book Internal Combustion Engines by John B.Heywood) $$ $$ Consider a reactive mixture of ideal gases. The reactant species M_a,M_b etc.and the product species M_l,M_m etc. are related by the general reaction whose stoichiometry is...
  28. K

    Creating Carpet Cleaning Solutions: Civil Engr or Chemical Engr?

    I want to create a company that makes carpet cleaning solutions and shampoos. I am currently a second year civil engineering student, strongly considering switching to chemical engineering in pursuit of my dream. I want to know if I need the chemical engineering training to go after such a...
  29. M

    Another: Simple Displacement Reactions & Balancing Chemical Reactions

    Homework Statement Complete the simple displacement reactions and balance any chemical reactions. Homework Equations Pb + NaCl → __________ + ____________ The Attempt at a Solution Pb + NaCl → PbCl + Na But I don't know which charge of lead to use: Pb2+ or Pb4+ to...
  30. M

    Simple Displacement Reactions & Balancing Chemical Reactions

    Homework Statement Complete the simple displacement reactions and balance any chemical reactions. Homework Equations copper + silver nitrate → __________ + ____________ The Attempt at a Solution Since copper on the periodic table can be Cu2+ or Cu+, my solution was copper + silver...
  31. A

    Chemical Potential: Formula for Finding Molecular/Atomic Potential

    What is the formula used to find out the chemical potential of a molecule or atom?
  32. A

    Looking for a better understanding of chemical reactions

    This is for self study. 1. Why don't some molecules react? For example, NH3 + CaCO3 2. Where can I find a good list of standart state enthalpy and entropy values for molecules? My Chem I teacher gave us all a pretty good handout, but that's been a while ago, and I don't know where it is...
  33. O

    Is it possible to work with pharmaceuticals as a chemical engineer?

    I am a high school senior, probably attending University of South Florida next year. Chemistry is my favorite subject and I am interested in working with pharmaceuticals, designing drugs and drug delivery systems, etc. I don't think I would like to do pre-pharm and go to pharmacy school, as I...
  34. Z

    Do I sound fine for Chemical Engineering?

    Hello. I appreciate the time given to read through this. I am ending a stressful self-defining process to choose my major! I knew I would have to decide my major this week. I have been extremely stressed about choosing Mechanical or Chemical engineering. While some careers in both disciplines...
  35. T

    Chemical engineering heat transfer qts

    Heat Transfer Qts Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature)...
  36. M

    Homework questions in Thermodynamics for Chemical Engineering

    1. State what is "Kauzmann Paradox" and provide your own explanation (or solution) for the paradox and derive a unique explanation using different approaches. 2. If you observe a phase transition phenomenon in your own experiment, how to determine the whether the transition is binodal or...
  37. N

    Chemistry Chemical Process Analysis - Mole Flow Rate

    Homework Statement 120 mol/min of Propane (C3H8) is burned in the presence of air (21% O2 and 79% N2) in a furnace, two reactions occur: Complete Combustion: 67%, propane is burned to CO2 and H2O Incomplete Combustion: 18%, propane is burned to CO and H2O Oxygen is supplied at 70%...
  38. I

    Doubts about potential energy, bonding and chemical reactions

    Hello everybody, First, sorry for the bad english, it is not my language. I have a few theoretical problems and I would be very thankful if you helped me. 1º: I see the graphic about covalent bonds and potential energy a lot of times and they always say that potential energy...
  39. T

    How Does Removing Ammonia Affect Chemical Equilibrium?

    Hi, I have simple question N2+3H2 = 2NH3 + heat How would the equilibrium position be affected if ammonia is removed from the vessel?, shouldn't it move to the left to produce more reactants and replace the ammonia? why does it move to the right?, because that's what my texbook says.
  40. F

    Chemical engineering, is it for me?

    I'm a college student 17 years of age; I'm at the point in life where I need to use what degree I want to do. I have chosen the following a levels: - Physics - Further maths - Chemistry - Maths At the moment I'm thinking of doing either chemical engineering or maths. I have always been...
  41. S

    Help required with chemical formula and spectrophotometry

    Hi guys, I have what I hope is a simple question. basically I have a known crystal structure with a known dopant, however I don't know what the charge on the dopant is and I can't find it in any papers. Now I'm not sure if this is something I just need to find or whether this is something I can...
  42. rakeru

    How do I balance this chemical equation with a fraction?

    Homework Statement Hi! I am currently learning how to balance equations in chemistry but something that I don't understand is using fractions to balance an equation. I have a problem that I can't work out because I'm so confused! The problem says: Complete and balance the acid-base...
  43. T

    Determine if chemical equation is exothermic or endothermic?

    How would I determine, if given a chemical equation is exothermic or endothermic? Eg. Mg + 2HCL\rightarrowMgCl2 + H2
  44. PhizKid

    How to multiply chemical compounds together?

    Homework Statement CuSO_4 \cdot 5H_20 Homework Equations The Attempt at a Solution We never learned this. I don't even know what it means to "multiply" compounds together...doesn't make any sense to me
  45. A

    How do you find the product of a chemical reaction?

    Homework Statement In a general sense, how do you determine what the product will be in a chemical reaction? In the first example, a gas evolution, you combine the cation of each compound and pair it with the anion of the other: HNO3(aq) + Na2CO3(aq) ----> H2CO3(aq) + NaNO3(aq)...
  46. K

    Difference between Chemical analysis and PMI

    Hi, What is the technical difference between chemical analysis and PMI(Positive material identification)? Is it different name only or chemical analysis is a separate test? I found that FRF analyser (X-Ray fluorescence technique) or Optical Emission spectrometer (spark type gun with ultra pure...
  47. D

    Gaseous Chemical Reactions and Volumes

    (Hi everyone! Apologising for the trivial(and likely boring) question in advance. Sadly, it has me boggled for some reason). Homework Statement In a certain temperature and under a pressure, 500 mL of H2, and 100 mL of O2 are poured into a container. A Chemical reaction occurs as follows...
  48. G

    Are lunar landings without chemical rockets possible?

    If a satellite tries to land on the moon without rockets to counter the force of gravity, it comes in too fast and crashes into the surface destroying itself. A satellite would be orbiting at approximately 1.8 km/s or so at a 50km altitude, and come in for landing from that height which would...
  49. M

    Chemical potential in Thermodynamics to find latent heat of vaporization

    Homework Statement The latent heat of vaporization of a substance is defined as the amount of heat required to transform the substance from its liquid into its vapor phase. A certain material has a boiling point of 700K and its molecules have three degrees of freedom in the liquid phase but...
  50. nukeman

    When looking at a Chemical, what does this mean 99.9 atom % D

    When looking at a Chemical, what does this mean... "99.9 atom % D" Hey, can someone explain to me what this means. Lets use D2o for example (Deuterium oxide) 1 store says "99.999 atom % D" And the other store simply says "DEUTERIUM OXIDE 100% D,99.96% " Can someone please shed some...
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