CBSE Class 9 Science Exam 2020: Important Practical Based Questions and Answers
In CBSE Class 9 Annual Examination 2020, Science question papers may have a few question based on practical skills. Such questions are expected in set of 1 mark or 2 marks questions. So, to deal with the practical based questions, students must be aware of important practical concepts.
We are providing here important practical based questions for class 9 Science exam. All these questions are provided with detailed answers to make it easy for students to understand the concepts used. Practicing with these practical questions will help students to acquaint with important concepts and enhance their practical knowledge so that they are able to solve questions in exams to get correct answer.
Given below is a collection of important questions based on practical skills to prepare for CBSE class 9 Science exam:
1. Mention the two precautions to determine the boiling point of water in laboratory.
(i) The position of bulb should be slightly above the water level.
(ii) Stir the water continuously in beaker so that temperature should remain constant
2. The frequency of a source of sound is 100 Hz. How many times does it vibrate in a minute?
Number of vibrations produced in 1s = 100
Number of vibrations produced in 60 sec = 100 × 60 = 6000
Now, 1 minute = 60 seconds
Thus, number of vibrations produced in one minute = 6000
3. In which of the two, glycerine or kerosene, the loss in weight of a solid when fully immersed in them will be more and why ?
Density of glycerine is more than that of kerosene.
A liquid having higher density exerts more upthrust force on object than other liquid having low density. Thus, greater the density of a liquid, the more will be the the buoyant force exerted on the object immersed in it. Now, due to this greater upthrust (buyont force), the object experiences greater apparent weight loss.
Thus in case of glycerine, the loss in weight of a solid when fully immersed in it will be more than when immersed in kerosene.
4. A sound wave travels at a speed of 340m/s. If its wavelength is 2 cm, what is the frequency of the wave? Will it be in the audible range?
It is given that,
Velocity of sound, v = 340 m/s
Wavelength, λ = 1.4 m
Frequency, ν =?
We know that, speed = wavelength × frequency
⟹ 340 = 1.4 x ν
⟹ ν = 340/1.4 = 242.86 Hz
As the audible range is between 20 Hz – 20,000 Hz
Here, 242.86 Hz < 20,000 Hz
Therefore it is in the audible range.
5. When dipped in a fluid, name the factor on which the loss in weight of a solid depends. Name the two forces which act upon the solid dipped in the fluid.
Loss in weight of a solid dipped in a fluid depends upon the density of that fluid.
The two forces which act upon the solid dipped in the fluid are:
- True weight of the body acting vertically downwards.
- Buoyant force or upward thrust acting vertically upwards.
6. In an experiment to determine the boiling point of water, state reason for the following:
(i) Pumice stone pieces are added to water in the beaker.
(ii) A glass stirrer is used.
(i) Pumice stone is added to avoid any bumping of water. When the temperature is raised for boiling the water, it starts to bump. But pumice stone being porous, provides space for air. This reduces bubbling in hot water to facilitate the boiling process.
(ii) A glass stirrer is used to ensure uniform heating of water.
7. A mixture of sand, powdered glass and common salt is dissolved in water and then filtered. Name the substance left on filter paper. Name the substance in the filtrate.
Out of the given three substances only common salt is soluble in water whereas both sand and powdered glass are insoluble in water. Thus when a mixture of sand, powdered glass and common salt is dissolved in water and then filtered sand and powdered glass would be left on filter paper while common salt will be present in the filtrate.
8. A free falling object eventually stops on reaching the ground. What happens to its kinetic energy?
Its kinetic energy will be zero on reaching the ground. Actually, when an object falls freely towards the ground, its potential energy decreases and kinetic energy increases. But as soon as the object touches the ground, all its potential energy gets converted into kinetic energy and finally when the ball stops after hitting the ground, all its kinetic energy gets converted into heat energy and sound energy.
9. Name the adaptation of fish which helps it in each of the following:
(i) Swimming in water
(i) Fish have fins for swimming in water.
(ii) They have gills for breathing in water.
10. A baby is not able to tell her/his caretakers that she/he is sick. What would help us to find out that the baby is sick?
Behavioural changes like constant crying, irritabilty, improper intake of food, low period of activeness and mood swings can help to determine that the baby is sick.
11. List any two precautions you must take while finding the melting point of ice and boiling point of water.
(i) The bulb of the thermometer should be completely inside the crushed ice.
(ii) The thermometer should not touch the wall of the beaker.
12. When a body hanging with the hook of a spring balance is immersed in a liquid, state the factor due to which the reading of spring balance decreases. Define the factor.
The factor due to which the reading of spring balance immersed in a liquid decreases is buoyant force or upthrust.
Buoyant force (upthrust) is the upward force exerted by any fluid upon a body immersed in it.
13. A student recorded the mass of dry raisins as 2.0 g and mass of raisins after soaking as 3.5 g. Calculate the percentage of water absorbed by raisins. Write one precaution for this experiment.
Mass of dry raisins = 2.0 g
Mass of raisins after soaking = 3.5 g
Mass of water absorbed = 3.5 – 2.0 = 1.5 g
Raisins should be well immersed in water instead of lying not on surface.
14. Mention two features adopted by birds which help them to fly.
Two features adopted by birds which help them to fly are:
- Streamlined body shape which helps them to cut the air flow.
- Light bones reduce their overall body weight to help in easy flight.
15. Which of the following will show Tyndall effect?
(a) Salt solution
(c) Copper sulphate solution
(d) Starch solution
Milk and starch solution are colloids and hence will show Tyndall effect.
16. When the wire of a guitar is plucked, what types of wave are produced in (i) air and (ii) wire? Give reasons in support of your answer.
(i) When the wire of a guitar is plucked, a longitudinal wave is produced in air due to the to and fro motion of string of guitar.
(ii) In the wire of guitar, transverse wave is produced as the particle vibrates perpendicular to the direction of motion.
17. Explain how both physical and chemical changes take place during the burning of a candle.
Wax of the candle undergoes the combustion process to produce light and heat along with the liberation of carbon dioxide gas and water vapour. This is a chemical change. As a result, the candle melts and its shape is deformed. This is a physical change. So, during the burning of a candle, both physical and chemical changes take place.
18. The given figure represents a tissue found in the human body.
(a) Identify the tissue and state its function.
(b) Mention any two locations where this tissue is found in the body.
(a) The figure shows simple columnar epithelial tissue. Its main functions include absorption and secretion.
(b) Simple columnar epithelial tissue forms the lining of the stomach, small intestine, colon, gall bladder and oviducts.
19. There are two nails; one sharp and other blunt with the point surface areas being 0.1 m2 and 1.5 m2, respectively. These nails are to be hammered into a wooden plank. Which nail will be hammered more easily if the force applied on hammer is 200 N for both nails? Also calculate the pressure required to hammer each nail.
Let nail A be sharper than another nail B. Thus, the surface area covered by the nail A is lesser than that of nail B. Therefore, more pressure will be produced on nail A leading it to move inside the wooden plank more easily than nail B.
Finding pressure required to hammer each nail
Now, Area of nail A = 0.1 m2
Area of nail B = 1.5 m
Force applied on both nails= 200 N
20. While verifying the laws of reflection of sound, a student measured the angle between the incident sound wave and reflected sound wave as 100°. What will be the angle of reflection?
Given that the angle between incident sound wave and reflected sound wave = 100°
⇒ angle of incidence (i) + angle of reflection (r) = 100o …(i)
But, according to the law of reflection of sound, the angle of the incident sound wave is equal to the angle of the reflected sound wave.
⇒ ∠i = ∠r
Thus, equation (i) becomes:
∠i + ∠i = 100o
⇒ 2∠i = 100o
⇒ ∠i = 50o
Thus, angle of reflection, r = ∠i = 50o