Previous Topic :Chemical And Physical Changes
Elements, Compound And Mixtures
Today let talk about Element, mixture and compound.
Let start with element
What is an element? An element is a substance which cannot be spit up into simpler substances by any chemical means.
These elements are arranged together according to their atomic number in a table called Periodic table.
I hope we all understand what a periodic table is? And if you don't, don't worry I will explain it when will get to periodic table. But simply it a table consist of elements arranged with their atomic number.top↑
The elements are divided into into two major groups and one minor group.
The major groups are metal and non-metal.
The minor group is metalliods that is they consist of both metal and non-metal properties e.g Silicon, germanium and boron. I will explain this better when will get to periodic table but for now let talk about Element.
Metal And Non-metal
Differences Between Metal
And Non-Metal (Only Their
a] METALS have high boiling and high melting points, while NON-METALS have low melting point generally.
b] METALS are always solids at room or ordinary temperature e.g all metals except Mercury which is liquid, while NON-METALS can be in any form but mainly gases most of the time e.g oxygen gas and hydrogen gas as in gas form and carbon as in liquid form and bromine as in solid form.top↑
c] METALS are good conductor of heat and electricity, all metals are good conductor of electricity and heat no matter how weak the metal is, while NON-METALS are poor conductor of heat and electricity except graphite.
d] METALS are malleable that is, it can be hammered into different shapes and metals are also ductile that is why metals can be drawn into wires, while NON-METALS are brittle, they are weak and because of that they cannot be hammered because they break easily.
What is a compound?:
A compound is a substance formed when two or more different element combine chemically together e.g marble as an example, I believe you know what a writing chalk is.
CaCO3 [calcium trioxocarbonate (iv) note: don't ever write 4 as in number, will explain better when will get to nomenclature.top↑
You know in the above compound CaCO3, We have three elements that makes up that compound (CaCO3), which are Calcium(Ca), Carbon(C) and Oxygen, all those three elements are joined together by chemical means and can only be separated by chemical means.
If I gave you a chalk now and ask you to bring out Calcium or Carbon or Oxygen, will you be able to ? The answer is NO a capital one but you can do so by using some specific chemical means.
We will soon get to separation
Other examples are CaCl, NaOH, Na2CO3, H2SO4 and so on........ .
What is a Mixture?
A mixture is a substance formed when two or more substances are physically combined together. These substance can be element or compound and they can be separated by physical means. E.g milk, Sodium chloride (NaCl) which is also known as common salt in water (H2O), etc.
Don't think because NaCl is a compound that it will be separated from water by chemical means, yes it can be separated by chemical means but not when it is in water, that is why I didn't put it under compound, it's a compound but It is a mixture when dissolved in water.
If you pour salt into water, the only way to separate it is by applying heat so that the water will evaporate and the salt will be left in whatever container you used.top↑
Differences Between Compound And
a] COMPOUND has a fixed, constant composition while MIXTURE has variable composition.
b] COMPOUND can only be separated by chemical methods while MIXTURE are separated by physical methods.
c] COMPOUND always requires a large amount of heat of formation while MIXTURE requires a little or no amount of heat of formation.
NOTE : Don't says because when you want to separate salt from water you applied heat, so physical changes requires heat,
Heat of reaction is different from heat of formation ...
d] COMPOUND has different properties from it constituent elements while MIXTURE has the sum of all its individual constituents.
We should stop here for the day next topic will be on separation techniques.
Question Of The Day
IS BLOOD A MIXTURE OR COMPOUND?
kindly use the comment box, that question has came out in like five different schools post utme. [U.I , FUNAB, UNIBEN, LAUTECH AND UNILAG] and other universities I can't remember right now. You can also read my advice on Admission Procedure
Next Topic : Separation Techniques