4.Explain the following giving examples.
(a) saturated solution
(b)
pure substance
(c) colloid
(d) suspension
5.Classify each of the following as a homogeneous or
heterogeneous mixture.
soda water, wood, air, soil, vinegar, filtered tea.
6.How would you confirm that a colourless liquid given to you is
pure water?
7.Which of the following materials fall in the category of a “pure
substance"?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
Mercury
Brick
Wood
(i) Air.
8.Identify the solutions among the following mixtures.
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water.
9.Which of the following will show "Tyndall effect"?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution.
10.Classify the following into elements, compounds and
mixtures.
(a) Sodium
(b) Soil
(c) Sugar solution
(d) Silver
(e) Calcium carbonate
(f) Tin
(g) Silicon
Answers
Answer:
a. At any particular temperature, a solution that has dissolved as much solute as it is capable of dissolving is said to be a saturated solution. Examples of saturated solutions are soft drinks and nitrogen in Earth’s soil.
b. A pure substance is one which is made up of only one kind of particles. It cannot be separated into different constituents by physical or chemical processes. Some examples of pure substances are bromine, nitric acid, calcium oxide, etc.
c. Colloids are heterogeneous mixtures in which the size of solute particles is intermediate between those in true solutions and those in suspensions and are big enough to scatter light. Some examples are: Milk, blood, paint, etc.
d. A suspension is a heterogeneous mixture in which the small particles of a solid are spread throughout a liquid without dissolving in it. The particles of a suspension can be seen by the naked eye. Some examples of suspension are Chalk – water mixture, flour in water, Milk of Magnesia etc.
Explanation:
Answer:
4) A.The term saturated solution is used in chemistry to define a solution in which no more solute can be dissolved in the solvent. It is understood that saturation of the solution has been achieved when any additional substance that is added results in a solid precipitate or is let off as a gas.
B.A pure substance is a form of matter that has a constant composition and properties that are constant throughout the sample. Mixtures are physical combinations of two or more elements and/or compounds. Mixtures can be classified as homogeneous or heterogeneous.
C.A colloid is a substance microscopically dispersed evenly throughout another substance.
D.A suspension is a heterogeneous mixture in which the solute particles do not dissolve, but get suspended throughout the bulk of the solvent, left floating around freely in the medium.
5)Homogeneous mixtures : Soda water, vinegar and filtered tea. Heterogeneous mixtures : Wood and soil
6)The boiling point and freezing point of the given liquid comes out to be 100°C or 373 K and 0°C or 273 K respectively under one atmospheric pressure, it confirms that the given liquid is pure water.
7)Ice, iron, hydrochloric acid, calcium oxide, mercury are pure substances as they have definite composition. Milk is a colloid and acts as a heterogeneous mixture hence is not a pure substance. Brick and air are made up of more than one substance hence they also don't fall in the category of pure substances.
8)A solution is a homogeneous mixture of two or more components with a smaller size than 1 nm. Homogeneous mixtures have only one phase.
Homogeneous mixtures – Seawater, air and soda water
Heterogeneous mixtures – Coal and Soil
9)(b) milk and (d) starch solution show Tyndall effect because they are colloidal solution. Whereas (a) salt solution and (c) copper sulphate solution are true solution. Their particle size is too small to scatter light.
10)Elements →
The elements are regarded as the building blocks of the universe.
Sodium, Silver, Tin and Silicon are elements.
Compounds →
It is a pure substance made up of two or more elements chemically combined in a fixed proportion by mass.
Calcium carbonate, Methane and Carbon dioxide are compounds.
Mixture →
It is a substance containing two or more substance in any proportion.
Soil, Sugar, Coal, Air, and seawater are mixtures.