CAUTION of burning magnesium ribbon
It is dangerous to look for long at the burning magnesium ribbon. The teachers should advise children not to stare at the burning ribbon.
Physical and Chemical Changes
Chemical change and Chemical reaction.
A change in which one or more new substances are formed is called a chemical change. A chemical change is also called a chemical reaction. example Carbon dioxide (CO2 ) + Lime water [Ca(OH)2 ] → Calcium Carbonate (CaCO3 ) + Water (H2O)When carbon dioxide is passed through lime water, calcium carbonate is formed, which …
Accompany a chemical change
one or more new substances are produced in a chemical change. In addition to new products,the following may accompany a chemical change:1 Heat, light or any other radiation (ultraviolet, for example) may be given off or absorbed.2 Sound may be produced.3 A change in smell may take place or4 new smell may be given off.5 …
A protective shield
You must have heard of the ozone layer in our atmosphere. It protects us from the harmful ultraviolet radiation which come from the sun. Ozone absorbs this radiation and breaks down to oxygen. Oxygen is different from ozone. Can we call the breaking down of ozone a chemical change?If ultraviolet radiation were not absorbed by …
RUSTING OF IRON
This is one change that affects iron articles and slowly destroys them. Since iron is used in making bridges, ships, cars, truck bodies and many other articles, the monetary loss due to rusting is huge.The process of rusting can be represented by the following equation:Iron (Fe) + Oxygen ( O2 , from the air) water …
Galvanisation
This process of depositing a layer of zinc on iron is called galvanisation. The iron pipes we use in our homes to carry water are galvanised to prevent rusting.
Stainless steel
Stainless steel is made by mixing iron with carbon and metals like chromium, nickel and manganese. It does not rust.
Crystallisation
Some substances can be obtained in pure state from their solutions by crystallisation.
Physical change
Physical changes are changes in the physical properties of substances. No new substances are formed in these changes. These changes may be reversible.
Explain why rusting of iron objects is faster in coastal areas than in deserts.
Rusting is the process in which of iron in the presence of moisture and air form a layer of a brownish substance called rust. Both air and moisture are necessary for rusting of iron objects. Due to the presence of the sea, In coastal areas, there is more moisture in the air. But, in the …
Explain why rusting of iron objects is faster in coastal areas than in deserts. Read More »