Write the physical and chemical properties of oxygen and nitrogen.

Physical properties of oxygen

• Nature: Oxygen is a colourless, odourless, non-poisonous and tasteless gas.
• Density: Oxygen is slightly heavier than air.
• Solubility: Oxygen is slightly soluble in water. Oxygen dissolved in water is used by aquatic plants and animals for respiration.
• Liquefaction: Oxygen can be liquefied into a bluish liquid at -183°C by applying high pressure.

Chemical properties of oxygen

(I) Oxygen is a chemically active gas. It reacts directly with nearly all elements except for inert gases and halogens.

(II) Action of litmus:

• We can observe the nature of a solution using litmus paper which is an indicator.
• Blue litmus changes to red in acidic solution and red litmus changes to blue in alkaline solution.
• There is no change in the colour of litmus paper in neutral solution.
• When moist blue and red litmus papers are lowered into a jar containing pure oxygen, then no change in colour of both the litmus papers is observed. This shows that oxygen is neutral.

(III) Combustibility:

• Oxygen does not burn but supports combustion.
• Combustion also commonly known as burning is a chemical reaction in which a substance reacts rapidly with oxygen to produce heat and light.
• The combustion of fuels like petrol and diesel is an example of burning.
• It has been observed that certain substances have to be heated to a certain temperature before they start burning.
• The lowest temperature to which a substance must be heated before it begins to burn is called its ignition temperature.

(IV) Reactivity:

• Oxygen reacts with metals and non-metals to form new compounds called oxides.
• The process of formation of these oxides is called oxidation.
• When an element burns in oxygen, the reaction is called an oxidation reaction or simply oxidation.
• Such a reaction involves the addition of oxygen to form oxide. Combustion is an example of oxidation.
• Oxidation can be of different types based on the rate at which different substances combine.

(V) Reaction of non-metals with oxygen:

• Non-metals like carbon, sulphur and phosphorous burn in oxygen to produce their respective oxides which are acidic in nature.
• Heat is released in this process.

(VI) Respiration:

• The process in which oxygen reacts with the digested food to form carbon dioxide, water vapour and energy is called respiration.

Physical properties of nitrogen

• Nature: Nitrogen is an odourless, tasteless and colourless gas.
• Density: It is slightly lighter than air.
• Solubility: Nitrogen is very slightly soluble in water. Its solubility in water is less than that of oxygen.
• Liquefaction: Nitrogen liquefies into a colourless liquid when compressed. On further cooling, it can be frozen into a white solid.

Chemical properties of nitrogen

• Nitrogen neither burns nor supports combustion. However, metals such as calcium and magnesium burn in an atmosphere of nitrogen to form their corresponding nitrides.
• Nitrogen is neutral to moist litmus.
• Nitrogen is itself non-reactive and does not react with most elements. The presence of nitrogen ensures that processes like the burning of fuels and the breakdown of food during respiration take place at a moderate rate.