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.

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 composition

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.

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.

Which of the following are compounds?

(i) CO (ii) No

(iii) NO (iv) Co

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.

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.

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, Chlorine

Mention any two differences between compounds and mixtures.

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

(j) Mercury

(g) Brick

(h) Wood

(i) Air