Chemistry Definition and 993 Threads

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. K

    Why is there a +R or -R effect?

    What I mean to say is that why are some substituent groups such that(during resonance) the pi electrons' delocalisation is directed away from it while some groups are such that delocalisation of pi electrons is towards those groups? Can you kindly give some examples too?
  2. J

    Programs Should I add on a Chemistry Minor?

    Hi all, this is my first post on here so if it is in the wrong section, I'm sorry. I have been a physics undergraduate now for two and a half years and I'm at the point now where I have some electives I can finally choose. I already have a Math minor finished, but I'm thinking about adding on a...
  3. L

    Looking for rigorous General Chemistry textbook

    I'm going to be tutoring next semester and I need a good general chemistry book to review. I used an old copy of zumdahl during general chemistry(not assigned text but worked fine) but I want a fresh look at the subject that is a little more rigorous mathematically especially. After a year of...
  4. T

    Organic Chemistry - Elimination/substitution

    Homework Statement I have this problem: I known that reaction with TsOH would replace -OH groups with TsO (substitution reaction). (Et)3N would therefore act as a base to abstract H to form an alkene. The problem is i know it should be an E1cb reaction but how do I obtain an alkene? I tried to...
  5. D

    Can Miralax and Thick-It be safely mixed for a dysphagia patient?

    So I work at an assisted living facility where part of my job description is to administer medications in the morning. There is one resident who takes Miralax (polyethylene glycol) mixed in with water once per day for constipation. This is a doctor's order, so he must get it every day. The...
  6. N

    Chemistry Math & Chemistry: Should I Pursue a 2nd Majors?

    I'm a freshman math major and I want to pursue a PhD in math after graduation. I've heard that the job prospects for mathematicians are better if you have a background in another field. So I want to pursue a second major- which I probably would have done anyway because science is awesome...
  7. M

    Is there an Understanding Physics style book for chemistry?

    Hello all, I am a chemistry/physics teacher and our school also is an IB school. I teach both IB chemistry and physics. I have enjoyed and found useful using Asimov's Understanding Physics as a text of sorts for the physics class. I supplement it with problems from other books and sources...
  8. Wyn

    Engineering Intro to the Physics and Chemistry of Materials by Naumann

    This is the book that is required for my materials science II class but I can't find this book, I can't even find the contents so I can find a similar book. Do you know any?
  9. V

    Selective precipitation, purity and yield of precipitate

    Homework Statement An aqueous effluent contains 12 M Cd2+ and 10 M Mg2+ as solution of nitrates. Current practice is use NaOH to selectively precipitate the metals. (a) Is it feasible to get 0 Cd impurities in Mg ppt by using NaF instead of NaOH (back up your answer with adequate calculations)...
  10. J

    Unbiased Physical Vapor Deposition

    I apologize if this seems ignorant, but I am at a loss and I need some assistance. I recently built a small vacuum PVD system (Ion source, argon, target material, substrate cradle, etc.) and was showing it to a colleague when it was noticed that my system was unbiased. It actually didn't occur...
  11. G

    Determine all of the Physical Chemistry Variables of the System

    Homework Statement A weather balloon is filled with Helium gas and released from the ground. It goes up 18km and achieves a diameter of 15m. Determine if the following values are greater than zero, less than zero, or equal to zero: ΔV, ΔP, ΔT, ΔU, ΔH, Ssys, surr, Stot Homework Equations ΔU =...
  12. 655piano

    Chemistry Chemistry or Physics? Advice for Senior in High School

    I'm a senior in high school and very interested in both chemistry and physics. I have a strong background in chemistry but I am starting to lean more towards a career in physics. Any advice for college classes or decision making?
  13. S

    Is My Reasoning for Aromaticity Correct?

    Homework Statement Homework Equations Huckel's Rule: 4n +2 pi electrons The Attempt at a Solution I'm having problems with the last molecule. I said that the first molecule was indeed aromatic because it has 6 pi electrons and obeys the 4n + 2 rule. The second one is not aromatic because...
  14. X

    What is the specific activity of the air inside the sealed warehouse?

    Can anyone please guide me how to find solution of this problem A 0.2-g sample of 85Kr gas, which decays into stable 85Rb, is accidentally broken and escapes inside a sealed warehouse measuring 40×30×20 m. What is the specific activity of the air inside?
  15. J

    In absolute need of help with chemistry labs

    I just got out of my chemistry lab class at school, and needless to say, I don't think I am going to get a good grade. Basically, I felt like a complete idiot today. My professor was getting frustrated with me because he thinks I wasn't listening to him (even though I was). I never in my life...
  16. Elvis 123456789

    Grams of solute needed to lower vapor pressure of solvent?

    Homework Statement Some KCl is dissolved in water at 25°C, where it completely dissociates. The vapor pressure of pure water at 25°C is 28.3 mmHg. Estimate the mass in grams of KCl needed per liter of pure water to reduce the vapor pressure of water at 25°C by 5%. Homework EquationsThe Attempt...
  17. S

    Solid State Chemistry Question Regarding Fermi Energy

    Hi there, I am new to electron theory, and have a question regarding fermi energy. The book I am reading plots the Fermi energy distribuiton function vs Energy for T=0 ( upper right graph in pcture) and for T not equal to zero. The book says that, when T does not equal zero, the decrease in the...
  18. S

    Organic Chemistry - Synthesis of Lidocaine

    In lab we had to synthesize lidocaine, and one of the steps involved reacting a-chloro-2,6-dimethylacetanilide with diethylamine to form lidocaine. My professor told us that diethylamine-HCl crystals would form and these would help us determine the lidocaine yield (since they form at a 1:1 mole...
  19. K

    When does resonance take place?

    As in what are the conditions for resonance (i.e. in oganic chemistry) to occur? Sometimes it occurs, sometimes it doesn't; for reasons unknown. A little help please? :/:olduhh:
  20. A

    Find the Molarity of a Solution Using Concentrated Ammonia (28% by Mass)

    Homework Statement Calculate the molarity of a solution made by adding 35.5 mL of concentrated ammonia (28.0 % by mass, density 0.880 g/mL) to some water in a volumetric flask, then adding water to the mark to make exactly 250 mL of solution. (It is important to add concentrated acid or base...
  21. J

    Atmospheric Temperature and Air Molecule Density Calculation

    Homework Statement At an altitude of 50 km, the average atmospheric temperature is 0C. what is the average number of air molecules per cm^3 of air at this atmosphere? Given formula: P(sub h) = P(sub 0) x e^(-Mgh/RT) = -(Mgh x 10^5)/2.303RT Assuming P = 1 atm at sea level and h in km...
  22. kelsey

    Programs Majoring in Chemistry & Physics: Guide

    i am looking for something that includes both chemistry and physics thank you
  23. Science2Dmax

    Does the amount of matter in the universe stay at a constant amount?

    I was wondering if matter stays at a constant amount. You cannot really destroy anything really because crushing it just turns it into smaller pieces of itself, decomposition turns matter int separate elements, vaporizing just turns matter into gas and burning is a combination of all of the...
  24. 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...
  25. B

    In Gibbs Free Energy, why multiply -T?

    When you get the equation for the Gibbs free energy, why do you multiply -T? Can't you multiply just T? I thought about this and came up with an answer of my own, which goes like 'Because its Gibbs 'Free' Energy, when you have that free energy ( \Delta G >0) you have the energy to do...
  26. K

    How Do I Correctly Name This Alkane?

    Homework Statement Provide an acceptable name for the alkane shown below. Homework Equations N/A The Attempt at a Solution I never get these right but...my guess would be 2-dimethyl-5-butononane? My reasoning: the longest carbon chain has 9 carbons so the base name would be nonane, there...
  27. K

    Organic chemistry hybridization and bond angles

    Homework Statement Determine the hybridization of the atoms labeled A, B and C in the molecule and the bond angles around them. Homework Equations N/A 3. The Attempt at a Solution A. Normally, I would say it is sp3 for oxygen since there are 4 groups attached to it including the lone...
  28. S

    Grade 11 Chemistry Problem about a Nonreaction

    Homework Statement If there is a reaction, write out the chemical equation for Hg(NO3)2(aq) + CH3COONa(aq) Homework Equations N/A The Attempt at a Solution The answer says that there is no reaction. I have absolutely no idea why not.
  29. R

    Where Can I Find Quality Inorganic Chemistry Videos for High School?

    Can anybody link some good inorganic chemistry video websites for a high school apart from Khan Academy Lectures. I found PatrickJMT for Maths videos quite useful. For physics there were many, e.g DrPhysicsA, Doc Schuster videos etc. Usually there are some like chemistnate and ben chem videos...
  30. 8008jsmith

    What are the Steps for Solving Organic Chemistry Resonance Homework?

    Homework Statement https://s.yimg.com/hd/answers/i/582779fb3e0b4cecab74f7adb74ed84e_A.png?a=answers&mr=0&x=1422153107&s=7d575e72049bd930d0e263cbd57eff58 The Attempt at a Solution I have attempted to solve it. But I don't know what I'm doing wrong.
  31. N

    Programs Astro vs Chemistry for Physics Major

    Hi all. I'm a prospective physics major, hoping to either go into particle physics or condensed matter research or enter tech if research doesn't turn out to be for me. I was wondering which elective I should choose for next semester--astro 101 or Chemistry 1 or CS 1? Will chemistry help me with...
  32. J

    Engineering Transition from Physics to Engineering?

    Hi there! I'm currently pursuing a Bachelors of Science in Physics with minors in both Applied Math & Chemistry and am considering a career in engineering. Now, before all of you engineers jump my case about physics isn't engineering or whatever, please be mindful I'm here for help about my...
  33. montoyas7940

    Organic Chemistry IR and NMR problem solving

    Homework Statement I am trying to help my daughter determine the structure of this carbon compound. It has seven carbons, 14 hydrogens and one oxygen. The oxygen must be in a ketone group. Also each carbon is different (as indicated by the carbon 13 NMR). Homework Equations The Attempt...
  34. Charles Stark

    Would taking a chemistry class help with physics?

    Ah ha! So I was looking through the physics classes I will have to take and noticed a lot of topics dealing with atoms and the like. Would it benefit me to take the first installment of basic Chemistry? I don't want to take the lab portion just the lecture section if it would be a tremendous...
  35. M

    Organometallic Chemistry -- Multistep synthesis question

    1. Question Start with a organometallic (Benzene)M(Co)3see picture below) and React it with R- to get A, Then react A with I2 to get B and react A with H+ to get C. What is A,B and C? 3. Attempt at answering the question. I am not sure about the hapticity of Benzene. ? But i am prety sure...
  36. A

    What is the independent variable in Boyle's Law?

    I asked my teacher, and I was told that volume is the independent variable, and that pressure is dependent. The textbook I'm using said the same thing. After looking up some graphs of the law, I found that both pressure and volume were used as independent variables. It seems counter-intuitive...
  37. E

    Standarization of a Sodium Hyrdoxide Solution

    Homework Statement Hello, I missed a lab before the break because I was really sick and I need help. I was given the data from my partners for the titration lab and I don't understand how to calculate the amount of potassium hydrogen phthalate used in each trial, amount concentration of the...
  38. A

    How to Calculate Energy for Atmospheric Molecule Reaction and Isolate Gases?

    The atmosphere consists of two toxic, and unfortunately abundant gases in our atmosphere. Carbon dioxide and methane. Carbon dioxide produced by factories are not needed in the atmosphere and cause harm. So is methane. Acegikmoqsuwy and I thought of an equation to solve this problem: CH4 + CO2...
  39. Y

    Chemistry Recommendation for Chemistry textbooks

    I want a good book on Physical Chemistry at 11-12(university or pre-un) grade level. It should include topics about bonding(VSEPR, VBT, MO) etc. I also need suggestions about some books on organic and inorganic chemistry.
  40. G

    Divided between physics and chemistry

    They say one way to torture a person is to give them choices. I feel this is partly true in this case. I have a goal in mind for either one: if I do physics, I'll pursue nuclear physics/engineering but I go the chemistry route: I'll do biochemistry/forensic science. I've done a lot of research...
  41. J

    How to Prepare an HCl Solution with pH 4.2 from pH 2.9?

    Homework Statement Knowing that HCl is strong acid we want to prepare HCl solution of pH=4.2.starting from a solution of pH=2.9.Explain briefly the procedure that should be followed to do this operation. Homework Equations pH=-log(H3O+) 3. The Attempt at a Solution [/B] I calculated: At...
  42. TheNerdConstant

    15 year old physics nerd bids everyone hello

    Hi I have been passionate about physics for the last 4 years self taught up to about the first year of university level. I have found this website because now, at this key point in my life i need the guidance and knowledge that people from scientific fields only posses. I am interested to meet...
  43. 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...
  44. C

    Engineering Chemical Engineering at Uni A: Which Option is Better?

    I wanted to do chemical engineering at a particular uni but was ineligible to enter any of the engineering programs (lets call this uni A). I have 2 options since that uni A is the only uni in my location which offers chem eng. 1) Major in chemistry at uni A and take similar units as chem eng...
  45. N

    What Are Some Good Beginner Chemistry Experiments to Try at Home?

    I know there are many recourses online. But I'd like your individual input/advice What are some good chemical experiments I can do at home? Thanks
  46. A

    How do you solve this stoichiometry problem? Is it possible?

    10.25g of a compound, including chlorine is then diluted. So there is 10.25g in the original compound, which is then diluted. 30mL of that solution is combined with an excess of AgNO3 to create 35.5g of AgCl. What is the mass percent of chlorine in the original compound/sample. I got 8.78g for...
  47. N

    What topics should I review before taking Gen Chem 2?

    I'm planning on taking a second semester general chemistry course in the spring, and I'm wondering what I should study before hand. Based on RateMyProfessor, my teacher is going to be super hard. I took the first semester general chemistry course and I got an A in it, but that was last fall...
  48. AdityaDev

    Electrochemistry: reference electrode

    Reduction half reaction : Cu2++2e- -> Cu(s) I have a doubt in using the reference electrode. For example if I have the calomel electrode (ESCE=0.24V) how do I use it with the copper half cell? Are these reactions correct? Cu2++2e- -> Cu(s) 2Hg+2Cl -> Hg2Cl2+2e- To get Ecell=0.24+ECu|Cu2+
  49. D

    Questions about the intersection between chemistry & physics

    I am in some real need of advice on the possibilities of my future plans. A bit of background, 32 years old, went back to undergrad at 30 and currently enrolled in a Bsc (hons) degree in Natural Sciences in the UK with my major subject as Chemistry. Plans to give my full effort to getting into...
  50. gracy

    Which Type of Bond is Strongest in Chemistry?

    Strongest bond in chemistry ionic ,covalent or metallic?Bond strength decrease in the following order covalent > ionic > metallic so i think strongest bond would be covalent bonding then comes ionic bonding and at last metallic bonding.Correct me if i am wrong.One more question is water/ice...
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