Is Matter Around Us Pure Test - 12

At an atmospheric pressure of exactly 760mm Hg (1 atm), the temperature at which a liquid boils is called the normal boiling point of the liquid. For water, the vapour pressure reaches the standard atmospheric pressure of 1 atmosphere at 100°C. So the normal boiling point of water is 100°C (212°F or 373K). As the altitude increases, the boiling point of water reduces. The boiling point of water at a high altitude is less than 100 degrees. So, boiling point of water at the top of a mountain where the atmospheric pressure is less than 1 atm less than 100 degrees.

(1) Centrifugation is used to separate denser particles and lighter particles from a mixture by using a centrifuging machine. The principle is that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly. It is used in dairies and home to separate butter from cream.

(2) A separating funnel can be used to separate the components of the mixture of immiscible liquids. Separation of oil from water by separating funnel.

(3) Chromatography is the technique used for separation of the components of a mixture that are soluble in the same solvent, which are  absorbed differently on the stationary phase, thus leading to their separation. So, Separation of pigment from natural colors by fractional distillation process.

(4) Fractional distillation is suitable for separation of miscible liquids with a boiling point difference of 25K  or less. Separation of components of air done by fractional distillation method.

(1) Sublimation is the phase transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase and vice versa. Separation of ammonium chloride from salt done by sublimation process.

(2) Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance. Separation of salt from water done by evaporation process.

(3) Magnetic separation is a process in which magnetically susceptible material is extracted from a mixture using a magnetic force. So, sand separated from iron fillings by magnetic separation process.

(4) Simple distillation is a procedure by which two liquids with moderately large (around 50°C boiling points can be separated. If the difference in their temperatures is less than 30 degree centigrade, fractional distillation process is used in separation of a liquid mixture into fractions differing in boiling point in the case of Benzene and Toluene.

(1) Centrifugation is a process which involves the application of the centrifugal force for the sedimentation of heterogeneous mixtures with a centrifuge, Fine mud particles suspended in water can be separated by centrifugation process.

(2) Water chlorination is the process of adding chlorine (Cl₂ or hypochlorite ) to water. This method is used to kill certain bacteria and other microbes in tap water as chlorine is highly toxic .

(3) Sedimentation  is the process of removal of suspended particles that are heavier than water by gravitational settling. Small pieces of metal in engine of a car can be separated by sedimentation process.

(4) Filtration is a process by which insoluble solids can be removed from a liquid by using a filter paper. Tea leaves extract from tea by filtration process.

Brass is a homogeneous mixture of copper and zinc. Gun powder is not a powder .It is a simple mixture of potassium nitrate , sulfur and charcoal. A solution is a homogeneous mixture of two or more substances. Air represents a solution in terms of science. Air is a mixture of gases as gases are liquified and then separated by fractional distillation.Statement A is false and statement B is true.

Mixtures is a substance which consists of two or more pure substances. So given statement is incorrect.

Adding of common salt (NaCl) to water is physical change as no new substance is formed and no heat is evolved during addition of salt in water. Also salt can be obtained by evaporation. 

Cooking of vegetables is a chemical change because a new substance is formed having new properties and heat is used to change the state. Cooked vegetable cannot be reversed back as raw vegetable.

Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂(g)
Sulfur will not react with HCl and it will not conduct electricity.
FeCl₂ is Pale blue-green. And H₂ is a colour less and odourless gas.

A compound is a substance formed when two or more elements are chemically bonded together. The property of compound has always different from its constituents. True solution is a homogeneous mixture.
Compound has a fixed composition. Mixture has a variable composition. So, compound is homogenous and mixture is heterogeneous.
A compound is a substance formed when two or more elements are chemically bonded together. So, formation of a compound is a chemical change.
Constituents of mixture can be separated by physical methods. So, Formation of a mixture is a physical change.