CBSE Class X Chemistry - Chapter 3, Metals and Non-metals
CBSE NOTES : POINTS TO REMEMBER
1. There are 115
elements known to now.
2. Brass and bronze are
highly sonorous and so used in making bells.
3. Silver is the best
conductor of electricity followed by Cu, Au, Al, and W (Tungsten). Mercury and
lead have low electrical conductivity due to high resistance.
4. Amphoteric oxides being
acidic as well as basic, turn red litmus blue as well as blue litmus red.
5. Alkalis turn
phenolphthalein pink and turn red litmus blue.
6. Metal oxides react
with acids to form salt and water.
7. At room temperature
metals like - Al, Zn, Cu, Mg, Sn, Pb form oxide on their surface and became
dull. Mercury forms red coloured oxide, HgO.
8. Non-metals gain
electrons to form negative ions in order to compete their octet ie., 8
electrons in their outermost orbit.
9. Metals tend to loose
electrons to acquire nearest noble gas configuration.
10. Iodine is a
non-metal but has metallic lustre.
11. Gallium (Ga) is a
metal which becomes liquid if kept on palm. It has very low melting point while
its boiling point is very high. Because of this property it is useful for high
temperature thermometers.
12. Tungsten (W) has the
highest melting point.
13. Graphite is the only
non-metal which is good conductor of heat and electricity.
14. Non-metals have
generally low density except diamond which has high density.
15. Non-metals generally
not firm alloys. Only exception is carbon which is alloyed with iron to form
steel.
16. Cinnabar is a bright
red naturally occurring form of Mercury sulphide, HgS. It is the chief Ore of
Mercury.
17. Blister copper is a
kind of impure copper having spots or blisters due to evolution of Sulphur
dioxide.
18. Sodium Chloride
(NaCl) does not exist as molecules but as aggregates of oppositely charged
ions.
Also Read:
- CBSE Guide with additional CBSE Guess questions - Class 10 Science, Metals and Non-Metals
- Metals and Non-Metals - NCERT Answers of Class 10 NCERT Science Chapter 3 exercise questions
Class 10 NCERT Science -
Metals and Non-metals
CBSE NOTES : terms
& Definitions
Metals
Metals are the elements
which are usually hard, malleable and ductile. They are sonorous and have
metallic lustre. Metals are also good conductors of heat and electricity.
Metals are mostly solids
with high density and high melting and boiling points. They can loose electrons
easily from positive ions.
Exceptions:
1. Some metals like
sodium and potassium, magnesium are the only metals which can be cut with
knife.
2. Mercury is the only
metal which is liquid at room temperature.
3. Lead, Sodium,
Potassium and Lithium are the only metals which are not ductile.
4. Pb and Hg are poor
conductors of heat.
Anodising
The process of forming
oxide layer on the surface of metal is called anodising. For example, aluminium
forms an oxide layer on its surface when exposed to air. This layer of
aluminium oxide protects aluminium from corrosion. The layer can be made thicker
with the help of anodising.
Aqua Regia
Aqua Regia is a mixture of conc. HCl and conc. HNO3 in the ratio of 3:1. It can dissolve gold and platinum although none of these two metals react with conc. HCl or conc. HNO3 alone. Aqua Regia is a strong oxidising agent due to the formation of NOCl (Nitrosyl Chloride) and Chlorine produced by a reaction of two acids. It is highly corrosive and fuming liquid. Therefore, Aqua Regia should be kept away from eyes and skin.
Non-Metals
Non-metals are those
materials which are found in all the three states (solid, liquid and gas), non-lustrous,
non-sonorous, and neither malleable nor ductile. These are bad conductors of
heat and electricity. The oxides of non-metals are acidic in nature. Non-metal
elements tend to gain electrons and form negative ions (anion).
Non-metals have
generally low melting and boiling points except diamond, graphite, boron and
Silicon which have high melting and boiling points.
Alloys
These are homogeneous
mixture of two or more metals, or a metal and a non-metal. For example, brass
is an alloy of Cu and Zn. Alloying is a very good method of improving the
properties of a metal:
(i) Alloys do not get
corroded or corroded to very less extent.
(ii) They are harder and
stronger than pure metal, e.g., gold mixed with copper is harder than pure
gold.
(iii) Alloys are less conducting
than pure metals, e.g., copper is a good conductor of heat and electricity
whereas its alloys like - brass and bronze are not good conductors.
(iv) The melting point
of an alloy is less than that of pure metals. For example, Solder, which is an
alloy of lead and tin, has lower melting points than either tin or lead. Solder
is used for soldering (welding) of electrical wires.
Amalgam
In an alloy, if one of
the metals is Mercury then the alloy is known as amalgam.
Minerals
Minerals are the natural
materials in which metals occur in the form of their compounds. Minerals are
found in the earth's crust and also in sea water.
Roasting
It is a process in which
the sulphide ores are converted into oxides by heating strongly in presence of
excess air. For example,
Calcination
It is a process in which
the carbonate ores are changed into oxides by heating strongly either in
limited or in absence of air. This process also helps to remove moisture or
volatile impurities. For example,
Flux
The substance which
reacts with gangue to form a fusible mass which can easily be removed, is known
as flux. For example, in the extraction of iron from ore, CaO (as lime) is used as flux to remove SiO2
(Silica) which is present as gangue.
Slag
This is the fusible mass
formed by the reaction of flux and gangue is known as slag.
Slag is lighter than
molten metal and so floats over the molten metal and can be easily removed. It
prevents metal from oxidation.
Froth
Flotation
Froth flotation is a
concentration process of selectively separating hydrophobic valuable minerals
from hydrophilic waste gangue. In mineral processing, Froth Flotation method is
used for the concentration of sulphide ores. The sulphide ore is mixed with
water and pine oil. The mixture is then agitated with the blast of compressed air.
In this process sulphide ore gets collected in Froth and gangue particles
settled at the bottom of the tank. Sulphide ore is thus, separated and dried.
Also Read:
CBSE Class 10 Science - Metals
and Non-metals
CBSE Guide
| CBSE NOTES : IMPORTANT CHEMICAL
REACTIONS
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