Page 100 - Chemistry - XI

Procedure

(a) Tensile strength of fi bres without using acids and bases
1. Take the threads of cotton, silk, nylon and terylene of same thickness and cut them into equal
lengths (20 cm).

2. Take the cotton thread (20 cm) and tie its one end to the clamp, fi xed in a vertical support at the top
of the other end of the thread to a small pan (weight hanger), the length of threads from top to pan
should be 15 cm after knotting in each case. Leave the hanger so that the thread gets suspended in a
vertical position. Put the small weight into the pan and increase more and more weights to the pan
till the thread breaks. Note the minimum weight required to break the thread.

3. Repeat the above procedure with silk, nylon and terylene threads to fi nd their tensile strengths.
4. Note the observation in table (1–4).

(b) Tensile strength of fi bres using acids and bases
1. Take volume of same molarity of HCl, CH COOH, NaOH and NH OH.
3 4
2. Cut thread of cotton, silk, nylon and terylene of same thickness (similar to the one used in procedure

‘a’ above) in equal 20 cm lengths, respectively.
3. Put these threads into the solution of HCl till they are soaked properly. Take these out from the
solution after 2 or 3 minutes and allow them to cool.

4. Now, determine the tensile strength of these threads in a similar way as in procedure (a) above.
5. Repeat the procedure (b) with CH COOH, NaOH and NH OH also, to fi nd the tensile strength of
3
4
cotton and silk.

Observations
Case I. Without using acids and bases
Vertical length of thread from hook to pan = 15 cm.

S. No. Name of Fibre Weight required to break the fi bre

1. Cotton 400 g

2. Silk 270 g
3. Nylon 1160 g

4. Terylene 580 g

Case II. By using acid and base
HCl
S. No. Name of Fibre Weight required to break the fi bre

1. Cotton 500 g
2. Silk 210 g
3. 3. Nylon 1750 g
4. 4. Terylene 705 g

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