What is Chemistry: Definition and 993 Discussions

Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant chemistry (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties of the soil on the moon (cosmochemistry), how medications work (pharmacology), and how to collect DNA evidence at a crime scene (forensics).
Chemistry addresses topics such as how atoms and molecules interact via chemical bonds to form new chemical compounds. There are two types of chemical bonds: 1. primary chemical bonds e.g covalent bonds, in which atoms share one or more electron(s); ionic bonds, in which an atom donates one or more electrons to another atom to produce ions (cations and anions); metallic bonds and 2. secondary chemical bonds e.g. hydrogen bonds; Van der Waals force bonds, ion-ion interaction, ion-dipole interaction etc.

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  1. A

    Chemistry, Finding Ionization Energies

    1. The ionization energies of Rb and Ag are 4.28 eV and 7.57 eV, respectively. Calculate the ionization energies of an H atom with its electron in the same orbitals as the highest energy electrons in these two atoms. Another way of thinking of this is: what would the ionization energies of RB...
  2. micromass

    Chemistry by Raymond Chang | Amazon

    Author: Raymond Chang Title: Chemistry Amazon link: https://www.amazon.com/dp/0077274318/?tag=pfamazon01-20
  3. C

    Solving Chemistry Problem: Reactions, CO2 & Volumes

    Homework Statement 40 cm3 of a gas was exploded with 40 cm3 of oxygen (known to be in excess). Under the conditions used, only hydrogen and carbon monoxide reacted with oxygen. On cooling the mixture to room temperature, the volume was 51 cm3. On adding concentrated KOH, the volume decreased...
  4. micromass

    Modern Quantum Chemistry by Szabo and Ostlund

    Author: Attila Szabo, Neil Ostlund Title: Modern Quantum Chemistry: Introduction to Advanced Electronic Structure Theory Amazon Link: https://www.amazon.com/dp/0486691861/?tag=pfamazon01-20
  5. micromass

    Physical Chemistry: A Molecular Approach by McQuarrie and Simon

    Author: Donald McQuarrie, John Simon Title: Physical Chemistry: A Molecular Approach Amazon Link: https://www.amazon.com/dp/0935702997/?tag=pfamazon01-20
  6. micromass

    Quantum Chemistry by McQuarrie

    Author: Donald McQuarrie Title: Quantum Chemistry Amazon Link: https://www.amazon.com/dp/1891389505/?tag=pfamazon01-20
  7. micromass

    Organic Chemistry by Clayden, Greeves and Warren

    Author: Jonathan Clayden, Nick Greeves, Stuart Warren Title: Organic Chemistry Amazon Link: https://www.amazon.com/dp/0199270295/?tag=pfamazon01-20 Level: Undergrad
  8. C

    Significant Figures and other basics in a Chemistry for Engineers class

    I'm hoping for verification here that I'm not crazy on some very very basic chemistry questions. I've worked 7 problems on a practice test (the real thing is next Tuesday). Only 2 of my answers agree with the answer key. Here are the most dramatic examples. Please tell me I'm not crazy...
  9. R

    Complcated Chemistry Reaction - impossible?

    Complcated Chemistry Reaction - impossible?? Help :( My notes say: Step 1 is a 221 reaction. If peroxides are used in your version, then the anti-Markovnikov bromide is formed. If your version had only HBr, the the Markovnikov bromide is formeed. Step 2 creates organolithium or Grignard...
  10. PhizKid

    Best introductory general chemistry text?

    Our class doesn't use a textbook and our professor doesn't give out much notes. Just handouts with problems on it. So I wanted a textbook to accompany my studies but don't know which is the best/rigorious general chemistry textbook.
  11. G

    Chemistry: SPPS/Protecting Groups(Boc/Fmoc)/Peptide Question

    Question with part of answer: http://i.imgur.com/5Nki1SM.png More answer with questions: C-terminus should a carboxylic acid for both as the ester and amide will be acid hydrolyzed. The ester linkage should be more susceptible to acid because it is more reactive than the amide. This is because...
  12. Greg Bernhardt

    Concise Inorganic Chemistry by J. D. Lee

    Author: J. D. Lee Title: Concise Inorganic Chemistry Amazon Link: https://www.amazon.com/dp/0632052937/?tag=pfamazon01-20 Prerequisities: Contents:
  13. 1

    Chemistry = looking up numbers then adding/subtracting them

    Homework Statement Attached Homework Equations Heat of reaction = Heat of formation of all products - heat of formation of all reactants The Attempt at a Solution 1.) It's 0 kJ/mol because it is. 2.) Every source agrees with 143 kJ/mol or 142.7 kJ/mol (which I've tried)...
  14. Ascendant78

    Resource for chemistry letter and symbol definitions/values in equations

    Homework Statement I have a chemistry teacher who discourages students from asking questions (long story, but he's just not a good teacher). We have an online textbook, which fails to explain a lot when it comes to formulas. One thing I want to understand is what the different letters and...
  15. L

    A few chemistry questions basically proportion calculations

    Homework Statement Chloroethane, reacts with Oxygen according to the equation below: 2C2H3Cl + 5O2 → 4CO2 + 2H2O +2HCl How many moles of CO2 are produced when 3.0 moles of choloroethane and 3 mol of O2 are...
  16. Greg Bernhardt

    Chemistry: The Central Science by Theodore L. Brown

    Author: Theodore L. Brown Title: Chemistry: The Central Science Amazon Link: https://www.amazon.com/dp/0130484504/?tag=pfamazon01-20 Prerequisities: Contents:
  17. Greg Bernhardt

    Physical Chemistry by Peter Atkins

    Author: Peter Atkins Title: Physical Chemistry Amazon Link: https://www.amazon.com/dp/0716735393/?tag=pfamazon01-20 Prerequisities: Contents:
  18. G

    Guess the Mechanism help (Organic Chemistry)

    "Guess the Mechanism" help! (Organic Chemistry) Homework Statement After identifying my reactants and products via spectral analysis, I am now tasked with figuring out the mechanism behind converting a diol into a ketone. Homework Equations The Attempt at a Solution The key to this appears...
  19. Greg Bernhardt

    Organic Chemistry by Robert T. Morrison and Robert N. Boyd

    Author: Robert T. Morrison, Robert N. Boyd Title: Organic Chemistry Amazon Link: https://www.amazon.com/dp/0136436692/?tag=pfamazon01-20 Prerequisities: No prerequisites Contents: User comments: https://www.physicsforums.com/member.php?u=331656: I can't really say much about...
  20. Greg Bernhardt

    March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure

    Author: Jerry March, Michael B. Smith Title: March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure Amazon Link: https://www.amazon.com/dp/0471720917/?tag=pfamazon01-20 Prerequisities: High-School Chemistry Contents: User comments...
  21. S

    Mean Free Path and Reactions (Atmospheric Chemistry)

    Hi, I have an exam tomorrow for atmospheric chemistry and I was just going over some past papers. In one it asks the following question, "What is meant by "Mean Free Path"? How is this relevant to atmospheric chemistry. My answer was as follows "The mean free path is the average distance a...
  22. M

    Chemistry pressure of gas problem

    1. A vessel that contains a gas has two pressure gauges attached to it. One contains liquid mercury, and the other an oi lsuch as dibutyl phthalate. The difference in levels of mercury in the two arms of the mercury gauge is observed to be 9.50 cm.Given density of mercury =13.60 g cm-3...
  23. U

    Chemistry- Basic Energy Transfer Questions

    Why does no temperature change occur while ice is melting? Specifially, when very little ice is left, how does so much water remain at 0 degrees Celcius? Is the energy transfer (of heat) to ice constant? Specifically, does the time range in an exponential manner for different sizes of ice to...
  24. K

    Boltzmann Distribution (Chemistry/ Physics)

    Homework Statement Okay i want to ask 2 questions. Question 1 Hyperstoichiometric compound Al3O has a vibrational energy spacing of 3.08x 10^-21J how many molecules are present in the ground state at 300k and 3000K Question 2 Calirimetric data for protein unfolding yielded following...
  25. R

    Chemistry Chemistry: Molecular Orbital Theory and Conjugation

    I am working my way through Ian Fleming's 'Molecular Orbtials and Organic Chemical Reactions' and I am having trouble with one of the exercise questions. (Ch2 Q1) It reads: Given that two pi bonds conjugated together have a lower energy than two separate pi bonds and a C-H bond conjugated with...
  26. O

    Interested in physics or chemistry but never learnt it.

    Hello, Since I can remember I have always dreamt of having an academic career and research. Theoretically physics seems very interesting to me and has always been my plan of what to pursue. The idea of knowing more about the world and discovering how it works is very enchanting to me. This...
  27. P

    U Waterloo Medicinal Chemistry Program

    I'm curious what your thoughts are on this program: https://uwaterloo.ca/science/current-undergraduate-students/majors-minors-specializations/medicinal-chemistry-co-op-only It's a new program at Waterloo. It sounds to me to be similar to pharmacology, but I was under the impression that...
  28. C

    Chemistry curriculum too heavily bio focused?

    I believe that the current chemistry curriculum has had a major increase in biological content in the past 10 years, and that this biological content has replaced valuable mathematical content. It used to be that the core classes of chemistry were, along with the basic math core of calculus...
  29. mrspeedybob

    Kitchen Chemistry. Cooking pasta

    My wife insists that pasta is not to be cooked with the lid on the pot. I reason that the cooking temperature must be fairly constant at the boiling point of water, so the energy required to cook the pasta can be reduced by putting a lid on the pot and turning the burner down just enough that...
  30. V

    Chemistry Special Branches of Physics & Chemistry that have scope in the future.

    I require some guidance on my career. My school offers a very vague stream sellection in the senior secondary section(Grade 11). I do wish to specialise in Physics or Chemistry as these subjects interest me quite a lot. To do so I must opt for the 'Science with Computer Science Group) at school...
  31. S

    Can You Transition Between Chemistry and Physics Careers?

    Hi everyone! A couple of questions for you. So, I'm thinking about pursuing a career in chemistry research BUT I also really like physics, so I'm not really sure which to choose... -If I were to get a physics undergrad degree, could I move into chemistry? -If I were to get a chemistry Ph.D...
  32. H

    Chemistry: Using Formation Constant to calculate an end concentration

    Homework Statement 50.0 mL sample of 2.0 10–4 M CuNO3 is added to 50.0 mL of 4.0 M NaCN. The formation constant of the complex ion Cu(CN)3 is 1.0 10^9. What is the copper(I) ion concentration in this system at equilibrium? The Attempt at a Solution I did a dilution and got the new...
  33. B

    [Chemistry] Salt in an acetic acid solution with copper

    Homework Statement Basically I'm doing a lab report where we place copper pennies in a solution of salt and vinegar. This should strip the copper oxide off the outside of the pennies, leaving the copper underneath shiny and looking "new". The problem is why we add the salt. Homework...
  34. Q

    Chemistry: Doubling Ammonia Concentration in 1L Dish

    In a dish with the volume 1 litre we have 0.3 moles of nitrogen, 0.4 moles of hydrogen and 0.1 moles of amoniac. How many moles of hydrogen should we add to the dish so we can double the concentration of the balance for amoniac,if the temperature does not change? So I find the concentrations by...
  35. Q

    Calculating Enthalpy and Entropy for H2+I2--> 2HI Reaction at 718 K

    Kp for the reaction H2+I2--> 2HI is 50.2 is 718 K. The ▲H (enthalpy) on standard conditions is 25 kJ mol^-1 .Use this information to find the enthropy of the reaction on 718 K...so I can findf free Gibbs energy from Kp,(in standard conditions) and therefore the standard enthropy..but how about...
  36. E

    Chemistry - desperately with buffer calculation.

    1. A buffer is prepared by mixing a 100.0ml of a 0.100M NH3 solution with a 0.200M solution of NH4Cl and making the total volume up to 1.000L of water. What is the volume of the NH4Cl solution required to achieve a buffer at pH=9.5 Ka of NH4+ = 5.6x10^-10 The textbook tell me that the...
  37. L

    Physical Chemistry 2: Best Book for Preparing & Acing the Course

    Hey guys, I hope this is the right spot to this. I don't want to get another infraction. I just got recently got out of my first physical chemistry class and am now thinking towards the second one. I'm wondering which book would be the best supplement to read over the break and help me get...
  38. Q

    Calculating Reaction Speed Changes: Second and First Order Kinetics at 298K

    The reaction A+B ->Products is of second order related to A ,and of first order related to B.The reaction occurs on 298 K.When A=0.75 mol L^-1 and B=0,8 mol l^-1 the speed of the consumption of A and B is 0.00347 mol l^-1 min ^-1.What will be the speed of consumption of A and B after these...
  39. S

    How Did Chemists of the Past Measure Elements for the Periodic Table

    Hello, how did chemists of the past know the weight of the elements to build up the periodic table without using new lab tecniques ? Have they transformed all the elements into gases and used Avogadro's law to obtain a relative atomic mass ? And how did they it was an element and not a...
  40. N

    Chemistry combustion analysis gas problem

    Homework Statement Complete combustion of a 0.0150 mol sample of a hydrocarbon, CxHy, gives 1.680L of CO2 at STP and 0.810g of H2O a) what is the molecular formula b) what is empirical formula Homework Equations pv=nRt The Attempt at a Solution a) mol of co2: n=pv/Rt=1 atm *...
  41. Q

    How to Calculate Equilibrium Pressures in a Chemical Reaction?

    Reacton between the substances is A+B--> 2C where Pa=3 atm,Pb=2 atm.The reaction moves to the right until 70 percent of B has reacted and we have the equilibrum.FFind Pa,Pb,Pc and the constant of equilibrum Pa Pb Pc So in the beginning...
  42. Q

    Chemistry question,constant of equilibrum?

    In 3000 K the constant of disintegration in the equilibrum of the reaction Cl2-> ( <-) 2Cl is 0.570 atm.In the equilibrum the reaction weighs 3 miligrams and is contained in a dish with volume 60 mL and the temperature is 3000 K.Find the total pressure. So I used p=n/V*R*T where n=m/M when M...
  43. N

    First year chemistry quantum mechanics question

    Hydrogen atoms are generated in an excited state where the electron occupies the 2p orbital. The excited sample of atoms then emits radiation that is directed to an unknown metal. The radiation ejects electrons with kinetic energy 8.77 x 10^-19 J. Given the data in the table below, identify the...
  44. Saitama

    Inorganic chemistry, need advice

    I am having a difficult time with this subject. There are so many things to rote memorize here and that's way too difficult for me to rote learn the things. There are loads of reactions, so many reactions for each group, different types of periodic trends, how one can learn or rather, rote...
  45. Q

    Basic thermodynamic chemistry, heat transfer

    Homework Statement How many grams of steam at 100 deg. Celcius would be required to raise the temperature of 35.8 g solid benzene from 5.5 deg Celcius to 45.0 deg Celcius? Assume that heat is only transferred from the steam (not the liquid water) and that the steam/water and benzene are...
  46. E

    Differential Equations in Chemistry

    Hello, I'm a mechanical engineering student working on my senior design project. It involves the automated correction of an electrolyte's chemistry. That being the pH, conductance, and zinc concentration. One of the tasks is to apply a "transient control analysis". This involves creating...
  47. P

    What is the significance of using electron-volts in chemistry?

    Hi all, My instructor in my college chemistry class continually refers to cell potentials (as in battery cell potentials) in units of electron-volts. Is there any case in physics or chemistry where this is correct? My understanding is that an electron-volt is generally a unit of energy, but...
  48. K

    Physical Chemistry: Kinetics and fluorescence

    Homework Statement Consider fluorescence (light emission from an electronically excited state of a molecule) in the presence of a quenching molecule M. Quenching refers to the removal of energy from an excited electronic state by collision, and so without light emission. A mechanism for such...
  49. B

    [Chemistry] Chemical Reaction, limiting reactants and result stoichiometry

    Homework Statement 609.5 grams of vanadium (II) oxide, VO, and 832 grams of iron(III) oxide, Fe2O3, react according to the equation, which substance(s) and how many grams of each would be in the tube after the reaction completes? 3 points Homework Equations Equation: 2 VO + 3 Fe2O3 -> 6 FeO...
  50. A

    What is the process of peptization in chemistry

    I read on a website that by washing a precipitate with too much de-ionised water; the precipitate is Peptized and thus some precipitate is lost. I am having a hard time understanding what peptization is? Can somebody please help me understand in simple terms for an A level student?
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