IJSO Solution 19-10-10

ISJO QUESTION WITHANSWER (19-10-10)

1.

A round pencil has length 8 units when unstreched and diameter 1/4. It is sharpened perfectly so that it remains 8 units long with 7 units section still cylindrical and remaining 1 unit giving a conical tip. Volume of the pencil now is (A*)

11 96

(B)

37  192

2

Sol.

(C)

7 64

(D) None

2

1  1   1  Req. volume =    7 +    (1) 3  8   8  7 22 11  + = = 64 192 192 96

2.

Sol.

A rectangular glass plate is placed on a piece of paper which has a sm all dot of ink. W hen ink-dot is seen from the upper side of the plate, then it appears appears to be above above 1 cm from the paper. paper. If the refractive index of glass is 1.5, then the thickness of the plate in cm will be : (A) 1 (B) 1.5 (C) 2.5 (D*) 3 Given : Refractive index of glass,  = 1.5 Real depth (t) – apparent depth (x) = 1 cm Thickness of the plate = Real depth (d) = ?

Re al depth



t

 = Apparent depth = x

 –1 =  –

t 1 x

1.5  – 1 =

tx x

1 1 or x = = 2 cm x 0 .5 Hence, Real depth, t = x t = 1.5 × 2 = 3cm

 0.5 =

3.

Spherical Spherical aggregate of soap molecules m olecules in the soap solution is called (A*) a micelle.

Sol.

(B) an ester.

(C) a molasses.

(D) a vinegar.

The hydrocarbon chains of soap soa p molecules are hydrophobic (water repelling), which are insoluble in water but the ionic ends of soap molecules are hydrophilic (water attracting). Hence, soluble in water. They arrange in a specific way, way, which leads to the formation of micelles.

4.

Bacteria are mico organism can not seen by naked eyes. Which are unicellular and porkaryotic in nature.These organism are having outermost layer cell wall is composed of (A) lipid and protein (B) cellulose and hemicellulose (C) chitin and fungal cellulose (D*) Mucopeptide / peptidoglycan