Explain the following giving examples:
(a) Saturated solution
(b) Pure substance
(a) In a solution the relative proportion of the solute and solvent can be varied. At a given temperature, when no more solute can be dissolved in a solution, it is called a saturated solution. The amount of the solute present in the saturated solution at this temperature is called its solubility. For example, In order to obtain a saturated solution of sodium chloride and water at 20°C, a maximum of 36 grams of sodium chloride can be dissolved in 100 grams of water.
(b) A pure substance is made up of only one kind of particles. All the constituent particles of a pure substance are the same in their chemical nature. These particles may be atoms or molecules. For example, sulphur is made up of only one kind of particles called sulphur atoms, therefore, sulphur is a pure substance. Similarly, water is made up of only one kind of particles called water molecules. All the elements and compounds are pure substances because they contain only one kind of particles. A pure substance cannot be separated into other kinds of matter by any physical process. A pure substance has a fixed composition as well as a fixed melting point and boiling point.
(c) A colloid is a kind of solution in which the size of solute particles is intermediate between those in true solutions and suspensions. Due to the relatively smaller size of particles, as compared to that of a suspension, the mixture appears to be homogeneous. But actually, a colloidal solution is a heterogeneous mixture, for example, milk. Because of the small size of colloidal particles, we cannot see them with naked eyes. But, these particles can easily scatter a beam of visible light.
(d) A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension can be seen with naked eye. The particles of a suspension are able to scatter a beam of light passing through them and make its path visible. When left undisturbed, the solute particles are able to settle down. This shows that a suspension is unstable. They can be separated from the mixture by the process of filtration.
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Two chemical substances X and Y combine together to form a product P which contains both X and Y
X + Y → P
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following statements concerning X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compound
(iii) X and Y are elements
(iv) P has a fixed compositionLakhmir Singh & Manjit Kaur - Chemistry
Two chemical species X and Y combine together to form a product P which contains both X and Y
X + Y → P
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species X, Y and P are correct?
(i) P is a compound.
(ii) X and Y are compounds.
(iii) X and Y are elements.
(iv) P has a fixed composition.NCERT Science - Exemplar
Write true or false for the following statements:
A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.Evergreen - Science
Which of the following are compounds?
(i) CO (ii) No
(iii) NO (iv) CoLakhmir Singh & Manjit Kaur - Chemistry
There are three substances X, Y and Z. The substance X does not have a fixed melting point or boiling point and it still shows the individual properties of its constituents. The substance Y is a pure substance which occurs in nature as such. The substance Y has a fixed melting point and boiling point but it cannot be broken down into simpler substances by any chemical means. The substance Z is also a pure substance whose properties are entirely different from those of its constituents. The substance Z can, however, be divided by electrolysis into two substances which belong to the same class of substances as Y.
(a) What type of substance could X be? Name one substance like X.
(b) What type of substance could Y be? Name one substance like Y.
(c) What type of substance could Z be? Name one substance like Z.
(d) Whish process involves absorption or release of an appreciable amount of energy: formation of substance X or formation of substance Z?
(e) Name the three groups into which all the substances like Y are divided on the basis of their properties.Lakhmir Singh & Manjit Kaur - Chemistry
Iron powder and sulphur powder were mixed together and divided into two parts A and B. When part A was heated strongly over a burner, then a substance C was formed. The part B was, however, not heated at all. When dilute hydrochloric acid was added to substance C, then gas D was evolved and when dilute hydrochloric acid was added to part B then gas E was evolved.
(a) What type of substance is B?
(b) What type of substance is C?
(c) Name the gas (i) D, and (ii) E?
(d) Write one characteristic property of gas D.Lakhmir Singh & Manjit Kaur - Chemistry
In the following set of substances, one item does not belong to the set. Select this item and explain why it does not belong to the set:
Hydrogen, Oxygen, Steam, ChlorineLakhmir Singh & Manjit Kaur - Chemistry
Which of the following are not compounds?
(a) Chlorine gas
(b) Potassium chloride
(d) Iron sulphide
(h) Carbon monoxide
(i) Sulphur powderNCERT Science - Exemplar
Two substances, A and B were made to react to form a third substance, A2B according to the following reaction
2 A + B → A2B
Which of the following statements concerning this reaction are incorrect?
(i) The product A2B shows the properties of substances A and B.
(ii) The product will always have a fixed composition.
(iii) The product so formed cannot be classified as a compound.
(iv) The product so formed is an element.NCERT Science - Exemplar