PRACTICAL SKILLS IN SCIENCE
SECTION - A
1. A student was asked by the teacher to mix the white of an egg with water taken in a beaker and then stir it well. The student would observe that:
(1) a pale yellow transparent solution is formed
(2) an opaque suspension is formed
(3) a translucent mixture is formed.
(4) egg white floats on the surface of water
2. Which one of the following is not the correct observation when a magnet is moved repeatedly through a mixture of Iron filings and Sulphur powder kept in a tray ?
(1) Most of the iron filings cling to the magnet at the poles.
(2) A black mass of iron sulphide is produced.
(3) Sulphur does not cling to the magnet.
(4) Sulphur powder is left behind in the tray.
3. The colour of the gas evolved on heating solid lead nitrate is :
(3) greenish yellow
4. Which of the following precaution is incorrect in the determination of boiling point of water ?
(1) The bulb of the thermometer should be kept about 4 - 5 cm above the surface of water.
(2) Pieces of pumice stone should be added to water before heating to avoid bumping.
(3) The final temperature should be noted carefully by keeping the eyes in line with level of mercury.
(4) The thermometer bulb should dip well below the surface of water. \
5. Four students set up the experiment on plotting the temperature-time graph of a hot body as it cools to room temperature. They all perform the experiment using identical apparatus, under identical conditions and plot their graphs on similar graph papers using similar scales. The teacher asks them to observe their graphs carefully and list down the (approximate) values of the angles, made with the time axis, by the tangents to their graphs, at the beginning and towards the end of their observations. The values, noted by them, were as follows:
6. While performing the experiment on determining the velocity of a pulse through a stretched string, a student has to choose from:
(i) a tightly knit thick cotton string of length 5 m or a woollen string of length 7 m.
(ii) a stop clock of least count 1 s or a stop watch of least count 0.5 s.
For best results he should prefer the combination of :
(1) cotton string and stop clock.
(2) cotton string and stop watch.
(3) woollen string and stop clock.
(4) woollen string and stop watch.
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