When two substances X and Y were made to combine, another substance Z was formed. Following observations were recorded :
(a) Large amount of heat was evolved when X and Y were made to combine.
Predict the nature of the substance Z.

Substances X,Y,Z and A are respectively

When two substances A and B are mixed together in a pestel and mortar, a large amount of heat is evolved and a new substance C is formed. C has the properties different from A and B. Is C an element, compound or a mixture?

A brown substance 'X' on heating in air forms a substance 'Y' when hydrogen gas is passed over heated 'Y', it again changes back into 'X'

there are three substance X,Y and Z , the substance X, does not have a fixed melting point or boiling and it still shows the individual properties of its constituents ,the substance Y has a fixed melting point and boiling but it cannot be broken down into simpler substance by any chemical means the substance Z is also a pure substance divided by electroysis into two substance which belong to the same class of substance 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) which process involves absorption or release of an appreciable amount of energy : formation of substance X or formation of substance Z.? ( e) Name the three group into which all the substance like Y are divided on the basis of their properties .

X, Y and Z are three substance, On passage of electricity through X, two substances A and B are formed, Y is a liquid which on evaporation generates C as a residue and D was vaporized. Z could not be split up into any simpler substances further. A is found to be a good conductor of heat and electricity while B was found to be a gas. it is possible to split C and D into simpler substances chemically. what do you infer regarding the nature of these substances with respect to composition?

Iron powder and sulphur powder were mixed together 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 them 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) state one characteristic property fo gas D. (e ) Write one test to identify gas E.

In hot pin test on a substance,the given observations were done by a student. a)Hot pin did not penetrate b)It left a purple bun mark. c)It gave the acidic smell. Then the conclusion is the substance is made with