important practicals in bio
Answers
Given below are some very important practical based questions to prepare for CBSE class 10 Science exam:
1. A student adds a spoon full of powdered sodium hydrogen carbonate to a flask containing ethanoic acid. List two main observations that he/she must note in his/her notebook about the reaction that takes place. Also, write chemical equation for the reaction
Answer.
Two main observations during the reaction are:
(i) Brisk effervescence
(ii) Sodium acetate is formed
Chemical equation for the reaction is:
2CH3COOH + Na2CO3 → 2CH3COONa + CO2 + H2O
CBSE Class 10 Science Board Exam: Important Short Answer Type Questions
2. Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction.
Answer.
Raw Materials Required For preparation of soap in laboratory are :
Vegetable oil
Sodium Hydroxide
Commom salt
Test to determine the nature of reaction mixture: When a red litmus paper is dipped in the reaction mixture, the paper changes its colour to blue. Hence, the reaction mixture of the saponification reaction is basic in nature.
3. Write two precautions to be taken while identifying different parts of an embryo of a dicot seed.
Answer.
(i) The slide should be properly focused.
(ii) Slide should be observed first under low-power magnification and then under high-power magnification of the compound microscope.
4. A student is to conduct an experiment to show CO2 is released during respiration. List two precautions that he/she must take for obtaining correct observation.
Answer.
Two precautions to be taken are:
(i) Germinating seeds (living) should be used.
(ii) The experiment set up must be air-tight.
5. A student focuses the image of a candle flame, placed at about 2 m from a convex lens of focal length 10 cm, on a screen. After that he moves gradually the flame towards the lens and each time focuses its image on the screen.
(a) In which direction does he move the lens to focus the flame on the screen?
(b) What happens to the size of the image of the flame formed on the screen?
(c) What difference is seen in the intensity (brightness) of the image of the flame on the screen?
leaf peel
binary fission in Amoeba
budding in yeast and hydra
identification of embryo of a dicot seed(pea, gram, or red kidney bean)