Question
What was the basic classification of element in ancient time? Name them.

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Similar questions

Calculate the molecular masses of the following compounds:
  1. Methane, CH4
  2. Ethane, C2 H6
  3. Ethene, C2 H4
  4. Ethyne, C2 H2
(Atomic masses: C = 12u; H = 1u)
What is chromatography? State its two applications.
Define solubility. How does solubility of a solid in water change with temperature?
Calculate the molecular masses of the following compounds:
  1. Methane, CH4
  2. Ethane, C2 H6
  3. Ethene, C2 H4
  4. Ethyne, C2 H2
(Atomic masses: C = 12u; H = 1u)
What is a physical change? Give an example of physical change.
Three different atoms of oxygen are represented as:

$^{16}_{\ 8}\text{O},\ ^{17}_{\ 8}\text{O}\text{ and }^{18}_{\ 8}\text{O}$

  1. What do the subscripts (lower figures) and superscripts (upper figures) represent?
  2. What factor is responsible for the change in the superscripts 16, 17 and 18, though the element is the same?
  3. What is the usual name for such atoms of an element?
  4. Give the nuclear composition of $​​^{18}_{\ 8}\text{O}$
What is the distillation process? What kind of mixture can be separated by distillation?
Atomic Number
Mass Number
Number of Neutrons
Number of Protons
Number of Electrons
Name of the Atomic Species
9
16
-
-
-
-
32
24
2
1
10
-
-
-
0
-
-
12
1
1
-
-
-
-
0
-
Sulphur
-
-
-
Give the formulae of the compounds formed from the following sets of elements.
  1. Calcium and fluorine.
  2. Hydrogen and sulphur.
  3. Nitrogen and hydrogen.
  4. Carbon and chlorine.
  5. Sodium and oxygen.
  6. Carbon and oxygen.
The substance X normally exists in a physical state which can flow easily but does not fill its vessel completely. It also turns anhydrous copper sulphate blue. When substance X is cooled excessively, it changes into a substance Y which has a fixed shape as well as a fixed volume. If, however, the substance X is heated strongly, it changes into a substance Z which has neither a fixed shape nor a fixed volume.
  1. Name the substances (i) X (ii) Y and (iii) Z.
  2. What is the process of conversion of X into Y known as?
  3. At which temperature X gets converted into Y?
  4. What is the process of conversion of X into Z known as?
  5. At which temperature X gets converted into Z?