Chemistry help???

Question

Can anyone tell me the differences between element, compounds and mixtures? also the difference between metals and non-metals.

and i also don't understand combustion and rusting. how many methods are there for rust prevention.

Thank a lot.

Answer 1

elements: pure substances made of only one kind of atom

compound: pure substances made of two or more different elements chemically combined with a definite composition. The only way to separate the elements is by a chemical reaction.

mixture: two or more substances physically combined with an indefinite composition. The substances can be separated by physical means (filtering, evaporation, use of a magnet, distillation, etc.)

metals: elements with few valence electrons compared to valence orbitals. Properties: they have luster (shine), conduct electricity and heat, flexible (malleable = can be pounded into flat sheets; ductile = can be made into wires), tend to lose electrons and form positive ions; may corrode when reacted with oxygen in a moist environment.

nonmetals: valence orbitals are almost filled. Properties: dull, insulate (instead of conduct), brittle, tend to gain electrons and form negative ions.

Combustion is the reaction with oxygen in the air to produce a compound containing oxygen (called an oxide) and water.

Rusting is the reaction of a metal (usually iron) with oxygen in the air to produce a metallic oxide.

There are a number of methods for preventing corrosion: coating with paints or other materials, coating with a thin layer of a less easily oxidized metal; connecting the metal directly to a sacrificial anode (a piece of another metal that is more acitve and therefore more easily corroded); allowing a protective film, such as a metal oxide to form naturally on the surface of the metal.

Answer 2

elements are the most basic building blocks and are found in the periodic table. C, N, O, Na, H are all elements

Compounds are made up of two or more elements chemically bound together.

Mixtures are 2 or more compounds, not bound together.

Several physical properties are used to differentiate between metals and nonmetals such as ductility and conductivity. Both metals and nonmetals are only elements. Metals are usually ductile and conductive while nonmetals are not (with the exeption of Carbon). They are seperated on the periodic table as far right are mostly non metals and the left are all metals (exept hydrogen).

combustion is given by the general formula:
CxHyOz + O2 ---> aH2O + bCO2
where a,b,x,y,z are all integers.

rusting is also known as metallic oxidation and is given by the general equation:
M + O2 ---> MOa
where a is an integer.

Don't know many methods for rust prevention. Keep the metal out of oxygen. Storing it under mineral oil or nitrogen would both work nicely.

Answer 3

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Answer 4

Some good answers here. An element is member of the periodic table, a combination of electrons, neutrons and protons ( or electrons and quarks but this is not yet standard pedagogy) which, in its lowest energy state is electrically neutral. The combinations form discrete particles called atoms. All atoms with the same electrical charge AND the same number of protons AND the same number of electrons would be the same element (the number of neutrons can vary). Elements can exist as atoms or as compounds: Helium is an element and a gas composed of atoms by themselves. Hydrogen is an element, a gas, but exists as pairs of Hydrogen atoms bonded together at normal conditions (like in a balloon). Bonding of two or more atoms makes a compound, they DON'T have to be different elements. Usually, compounds are only considered to exist if they are stable for a reasonable length of time, similarly with elements whose atoms have to be "reasonably" stable. The time length which we would agree to be reasonable is DIFFERENT for atoms (elements) and compounds. Almost any time at all will do for an element, even millionths of a second, while a compound would have to exist for much longer for it to be considered a compound. (At least by most chemists, I think). If I put hydrogen and helium in a balloon I get a mixture. I can change the amount of one or the other independently. But some mixtures, (like distilling alcohol moon-shine) will be a fixed amount of its components (moonshine is ethyl alcohol and water - and some impurities). So, mixtures are generally, but not always, of variable composition. Metals and nonmetals are a little bit funny: and astronomer and a chemist will not agree on what is meant by the term. In chemistry, a metal is a substance which has electrons high enough in energy to jump the band gap and allow the material to conduct electricity. And non-metals do not. There are what chemists call organic metals which are compounds that condust electricity. The smart reader will note that since atoms are made of electrons, that ALL atoms will conduct electricity, but here we are talking about being able to conduct with less than a certain amount of resistance. I've forgotten the rough value which we agree to use to separate metals from non-metals. So, when an element or compound has a certain "geometry" or "structure" (its electronic configuration) and can conduct an electric current with little resistance, it is considered a metal. Everything with more resistance is considered a non-metal (or semi-conductor but thats a different subject). The classical metals like iron or aluminum exist in arrays of atoms. They form bonds, called metallic bonds with their neighboring atoms but these are not usually considered compounds since these arrays can be mixed to form alloys and usually the mixtures can be in any proportions you choose. Sometimes specific proportions occur and these would be considered compounds (and metals, too). There are three types of chemical bonding: metallic, covalent (like hydrogen pairs) and ionic (like salt - sodium chloride). Ionic compounds have some atoms with a positive charge attracting (pairing up with) atoms with a negative charge. Combustion is the process of burning an element, compound or mixture. Its gives off heat and chemically combines the atoms with Oxygen (another element existing as the compound O2 [or a pair of oxygen atoms bonded together]) The most famous combustion is burning carbon (like a diamond or graphite) to form carbon dioxide: C + O2 -> CO2. Carbon, an element exists in a diamond as a crystal, an non-metallic array of atoms covalently bonded together. Is it a compound? Hmm. a tough one! Yes, sort of. But it doesn't have a definite formula! (unless you just use the symbol C) O2 is a compound and CO2 is too. The real structure of CO2 is O-C-O. THis is the infamous greenhouse gas. (the lines show which atoms are bonded).
Rusting used to be used only for iron or steel oxidation. 4Fe + 3O2 -> Fe2O3. Now-a-days, rusting can mean the oxidation (combining atoms with oxygen in covalent bonds) of different metals. Does Aluminum rust? depends on your age and education. I say no it oxidizes but doesn't rust, younger people might beg to disagree. When oxidation (oxidizing) or rusting occurs fast enough it can give off a lot of heat. That can be called combustion - so yes steel can burn!
Maybe you were taught the fire triangle in school? It takes 3 things for a fire: Energy (a spark, flame or heat), Fuel and Oxygen. take away any one and there is no fire. Well as I said, oxidation or rusting is just a slow burn so if we take away the oxygen or separate the metal from the oxygen with oil or paint we protect it from rusting. Galvanized iron (in canned food) protects the steel can in two ways: 1) the zinc coats the iron and keeps oxygen away and 2) the zinc oxidizes and gives off electricity which protects the iron from rusting (complicated!). Ther are probably thousands of ways to prevent rust. One way is to run an electrical current through it, another is to coat it or keep it too cold to rust (this is really hard to do!). One way to coat it is to add a little Chromium (a diferent element) to the metal. The steel becomes "Stainless steel" (maybe you use it to eat with?) and the Cr coats the steel surface and protects the iron from rusting. And oh my there are so many other ways...

Answer 5

Element- the primary form of matter without other factors like radiation to break down the particular particle.
Compounds- combinations of elements binded together by electric charges (ionic) or by bonding (mo;molecular) together. A material that contains two or more substances, whether homogeneous or heterogeneous.
-metals- generally solid execpt for Mecrucy and are solid at room temperature and good conductors of electricity.

Answer 6

elements are found on the periodic table, they cannot be broken down to anything else

compounds are made of diff elements stuck together
mixtures are compounds, cept u can separate these without fancy equipment ^_^

metals= metals, they are found in the middle section of the periodic table, the part where it "sinks in"

the non metals are on the right of the metals; like by oxygen and carbon

the far left 2 columns are alkaline metals

Answer 7

Combustion forms only carbon dioxide and water. Rusting occurs when something is oxidized, meaning it is losing electrons (or gaining a positive charge).

Answer 8

element is a substance consisting of only 1 type of atoms...
eg: Na,Cl,Fe etc...(all those in periodic table)

compound is a substance consisting of two or different types of atoms..
eg:NaCl is a mixture of atoms of Na and Cl hence its a compound...

mixture consists of many atoms whether in reacted form or unreacted form..
Eg: alloys,other salts or substances containing many elements..

metal is one which is able to give away electron easily...and has a positive valency usually..
eg:Na,K,Rb, Mg etc..

non metals are usually electron acceptors and are near to inert gases in the periodic table..
they have negetive valency..
eg: Cl,Iodine etc..

combustion is burning in oxygen and takes place fastly..whereas rusting is reaction with atmospheric oxygen(moisture generally called) and takes place slowly..

hope u r satisfied..