Wednesday 7 November 2012

Metals, Non-Metals and Carbon, std 8 to 12 CBSE GSEB

Metals, Non-Metals and Carbon .
Revision of properties of metals and non-metals.
Carbon .
Occurrence, allotropes of carbon (diamond, graphite, coal etc.).
Reason of allotropy, physical and chemical properties of carbon.
Uses.
Properties and uses of calcium carbide.
Properties and uses of silicon carbide.
Carbonates and bicarbonates.

Tests. Sodium bicarbonate and sodium carbonate. 

Historical aspects of metals.
1. Pre-historic man used weapons made of stones, bones and horns for his living. Later on he started using weapons made of metals.
2. Egyptians started using gold for the first time around 14th century B. C.
3. During the period of early civilization (around 3500 B.C.) articles made of copper and tin were being used.
4. Period around 2500 B. C. was called Bronze age.
5. Asians around 200 B. C. and Chinese around 900-500 B.C. were using Iron.
6. Iron pillar near Qutubminar in Delhi was installed in 4th century B. C. Even today its rust-free grandeur is un-paralled.

Metals and Non-metals.
Many materials that we use in our daily life such as glass, cement, vessels, ornaments, electrical equipments, paper, paints, perfumes, medicines, synthetic fibers etc., are made of the naturally occurring 90 elements, their compounds and their mixture.
You have studied in previous chapters about some elements and the compounds.
Elements are classified as metals and non-metals based on certain general properties. About 80% elements are metals !

Activity :
Make a list of metallic and non metallic substances that are used in your home. Write their uses. 
Properties of metals and non-metals. 
In the previous classes, you have studied the general properties of metals and non-metals. Let us review some of them once again.
Note : 
Element with highest atomic number (92) is Uranium. two elements having atomic number less than 92 are not occurring in nature. 
They are Technician and Astatine. 
Chemical properties of Metals and Non-metals
Note:
Elements which have the intermediate properties (i.e., between metals and non metals ) are called Metalloids.
Eg. : Germanium, Arsenic.

Know the meanings
Acidic oxides
Basic oxides
Covalent compounds
Oxidising agents
Reducing agents 

Elements
Metals 
+O2
Basic oxides
+H2O
bases 

Non-Metals
+O2
Acidic oxide
+H2O
acids

Experiment 7.1
Take 2-3 pieces of zinc in a test tube. Add a little quantity of dilute sulphuric acid to it. Tie a balloon to the mouth of the test tube immediately. Observe the small bubbles rising in the acid and the balloon becoming bigger.
Reason it out.

Activity 7.2 
Try to cut sodium using a knife. 
Tell your experience and conclusion.
Caution : Sodium is highly reactive element. Touching it with bare hands is dangerous.

Activity 7.3
Beat a piece of tin several times with a hammer. 
Tell the changes that occur in its shape. 
Which property does it exhibit ?

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