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NCERT Solutions for Class 10th Science

 

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Chapter 3. Metals and Non-metals

Chapter Review

 

 

 

Chapter Review:


  • Metals, in their pure state, have a shining surface. This property is
    called metallic lustre.
  • Some metals can be beaten into thin sheets. This
    property is called malleability.
  • The ability of metals to be drawn into thin wires is called ductility.
  • Gold is the most ductile metal a wire
    of about 2 km length can be drawn from one gram of gold.
  • The metals that produce a sound on striking a hard surface
    are said to be sonorous.
  • The best conductors of heat are silver and
    copper. Lead and mercury are comparatively poor conductors of heat.
  • Full Form of PVC is polyvinylchloride.
  • Gallium and caesium have very low melting points.
  • Iodine is a non-metal but it is lustrous.
  • Diamond, an allotrope of carbon, is
    the hardest natural substance known and has a very high melting
    and boiling point.
  • Graphite, another allotrope of carbon, is a conductor of electricity.
  • Lithium, sodium, potassium are so soft that they can be cut with a knife. They have low densities and low melting points.
  • Metals such as potassium and sodium react so vigorously that they catch fire if kept in the open.Therefore they are kept immersed in kerosene oil.
  • Anodising is a process of forming a thick oxide layer of aluminium.
  • Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1.Aqua regia is a highly corrosive, fuming liquid.
  • The metals at the top of the activity series (K, Na, Ca, Mg and Al) are so reactive that they are never found in nature as free elements.
  • The metals in the middle of the activity series (Zn, Fe, Pb, etc.) are moderately reactive. They are found in the earth’s crust mainly as oxides, sulphides or carbonates.
  • Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand, etc., called gangue.
  • Cinnabar (HgS) is an ore of mercury.
  • The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting.
  • The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination.
  • Galvanisation is a method of protecting steel and iron from rusting
    by coating them with a thin layer of zinc.
  • The rusting of iron can be prevented by painting, oiling, greasing,
    galvanising, chrome plating, anodising or making alloys.
  • When iron is mixed with nickel and chromium, we get stainless steel, which is hard and does not rust.
  • An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.
  • Pure gold, known as 24 carat gold, is very soft. It is, therefore, not suitable for making jewellery.
  • The alloy of mercury is known as an amalgam.
  • The extraction of metals from their ores and then refining them for use is known as metallurgy.

 

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