GCSE Science and Maths revision

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aadil77 said:
sorry Rooh the catalyst is not 'iron oxide' that is used in making ammonia, the catalyst used in making nitric acid is platinum
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okay :confused: so what is the catalyst used to make ammonia :?...

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a fairly simple one:

What is the group of elements with full outer shells called?
 
Dhul-Fiqhar said:
What is the group of elements with full outer shells called?
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they are called the noble gases. they are in grou 8 and are unreactive.

wat are the group 7 gases called...name all of them (without refering them to a periodic table)...also, give electronic onfiguration of each.

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:sl:

Group 7 elements are called "Halogens"

They are:
  • Flourine
  • Chlorine
  • Bromine
  • Iodine
  • Astatine

dont know the configurations of each.....
 
volume is (pii x radius^2 x length) sorry difficult to type maths symbols
 
hibah786 said:
B. The Surface Area Of A Cylinder
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a cylinder has two circles...ie the two surfaces...and the tubical (?) surface...to find the surface area of the two circles, use the normal circle area formula ie...area= pi x radius^2
timesthe answer by two to find out the surface area of both the circles.

to find the surfac area of the cylinder body, find te circumference of the circle which is...2 x pi x radius...times the answer with the lenth to find out the surfce area of the cylinder body (aka the 'tubical' surface).

and this answer with that of the 2 circles calculated in the first part...and you should get the answer.

I Have No Idea On How To Balance Equations In Chesmitry Plz Help
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to understand that, you must first understand how to calculate the number of atoms in a compound.

to begin, tell me the number of oxygen mlecules and the number of hydrogen molecules in the water fomula

^that question is for sis hibah786 only.

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A7med said:
^ its an "on" with an "I" at the beginning
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funny.

What is an "Ion"?
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when an atom loses its electron or gains an electron to an element, it becomes charged and beoms an ion.

is that right?...i know what an ion is but explaining what it is is kinda hard.

next question:

explain ionic bonding and give an example of one.

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:sl:

Ionic bonding is when two atoms bond together by losing/gaining an atom, groups in the periodic table should also be put into consideration when the Ionic bonding is concerned.

The groups are to show the outer most electrons in the final shell of an atom, for example, Na (sodium) is in group 1, and hence has 1 electron in the outer shell. Sodium has 11 electrons, in order for an atom to be stable, the electrons in the shells must satisfy this ordering: 2(first shell):8(second shell):8(third shell):18....and so on, in this case it will have 2:8:1.

So now, in order to become stable it must react with an element from group 7 to satisfy 8 electrons in the outer shell. However, because there is only 1 atom, it is easier to give away that one electron to the other element in group 7 in which the G7 element satisfies the 8 in the outer shell pattern.

Electrons are negatively charged, and protons (in the nucleus) are positively charged, and because the negatively charged electron has been lost there are 8 protons (+ charged) so the Na atom now becomes a positively charged atom.

:D

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Now that.....I do not have an explanation to ;D

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PS. Eager to find out though....bring on the jargon :D
 
Dhul-Fiqhar said:
Explain what "emulsification" is?
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for double science, we dont really need to know much about this topic except the example about oil and water. because they cannot be mixed together, they are immiscible. they can only be mixed for a short while when you shake them up. this type of mixture is called an emulsion. in salad cream, the egg yolk is known as the emulsifying agent. food (such as chocolate) contain E numbers which are emulsifying agents.

whilst revising this topic, i had a look at the triple science bit, and found out about colloids. a colloid is a finely dispersed mixture of two or more substances that do not dissolve into each other.

next:
  • Multiply out and simplify the following:
    (3x - 1)(2x + 5)
  • 2mr2 + lmr
  • x2 + 9x + 18
have fun.

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1. 6x^2 + 13x - 5, x= 1/3 and x= -3/2

2. rm(2r + l)

3. (x+3)(x+6), so x= -3 and x= -6
 
emulsification is the break down of fats into smaller droplets (e.g due to bile)
 

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