This article contains some important practical based questions class 10 science. Section B of class 10 science paper will have questions from practical components. This will have 6 questions of two mark each in Section B. So, students are advised to prepare accordingly for this section as well.
Practical based questions class 10 science
- Dry ammonia gas has no action on litmus paper but a solution of ammonia in water turns litmus paper color. Why?
Answer. A solution of ammonia in water produces OH– ions which make the solution basic and turn red litmus paper blue.
- State the pH of distilled water and rainwater. Justify your answer with proper reasoning.
Answer. The pH of distilled water is 7 because it has no dissolved minerals. The pH of rainwater is slightly acidic less than 7 because it becomes a little acidic due to CO2 and SO2 molecules present in the atmosphere.
- Write any two precautions while performing the pH experiment?
Answer. Wash the dropper with water after each use or use new dropper for different samples. Keep the pH paper away from chemicals while doing the experiment.
- On opening the soda water bottle the dissolved CO2 comes out, would the pH of the solution increase or decrease as the gas comes out? Give reason.
Answer. The pH of soda water increases. Because soda contains carbonic acid which is the weak one. When CO2 escape the carbonic acid’s strength weakens and therefore pH would increases.
- Write any two precautions to study the reaction between Zn and HCl?
Answer. Acids should be handled carefully. Hydrogen gas evolved is highly
inflammable, so it should be handled carefully.
- Hydrogen gas is neutral to litmus paper. Explain how?
Answer. It is neither acidic nor basic. It does not affect blue and red litmus.
- What is the color of zinc metal? What happens to its color when zinc reacts with the hydrochloric acid?
Answer. Silverfish gray. When zinc reacts with HCl, the resulting solution becomes colorless (white) and zinc turns into black colored zinc chloride.
- A student took solid quicklime in a china dish and added a small amount of water in it. State the type of sound produced in the reaction. Mention the type of reaction?
Answer. The hissing sound is produced as it is an exothermic reaction. Combination reaction.
- Write two precautions that must be taken while studying the decomposition reaction, when the ferrous sulphate crystals are heated in a boiling tube?
Answer. Keep your nose away from the gas like SO2 which is suffocative. Use tube holder to heat the test tube.
- A student prepares aqueous solutions of the following salts:
Copper sulphate, ferrous sulphate, sodium sulphate and barium chloride.
Write the color of each solution thus formed?
Answer. Copper sulphate (aq) – blue in color
Ferrous sulphate (aq) – pale green in color
Sodium sulphate (aq) – colorless
Barium chloride (aq) – white in color
- Suppose the ammeter or voltmeter you are using in the Ohm’s law experiment does not have +ve and –ve terminal markings. How will you use such ammeter or voltmeter in the circuit?
Answer. We will use a typical battery to determine this. Connect them with wire and the battery if their readings are positive then we have connected them correctly and if their readings in negative then we have connected in opposite polarity.
- Mention any four precautions while doing an experiment to verify Ohm’s law?
Answer. All connections should be kept tight. The zero error in the ammeter and voltmeter should be noted down and taken into consideration while reading the measurement.
The bare ends of the connecting wires should be rubbed and cleaned properly with sandpaper.
The value of the current through the circuit should be kept as low as possible otherwise heating of the resistor occurs.
- While performing an experiment to study the dependence of current on the potential difference across two ends of the resistor, a student keeps the circuit closed for a long time to measure the current and potential difference. State how the resistance of the resistor will be affected?
Answer. When the circuit is closed for a long time, the flow of current will be in excess which causes unwanted heating in the resistor and changes the value of resistance.
- In an experiment on studying the dependence of current flowing through a given resistor on the potential difference applied across it, list two ways how a student would change the values of current in the circuit?
Answer. There are two ways in which a student can change the values of current in the circuit:
By increasing or decreasing the number of cells.
By changing the value of resistance.
- Mention any two characteristics of epidermal cells?
Answer. It forms the outermost layer of the leaves. Stomata are embedded in epidermal cells.
- In an experiment to prepare the temporary mount of leaf peel, staining of leaf peel is done before putting a drop of glycerine. Explain why?
Answer. Staining is meant to highlight the structures. Once glycerin is poured, it forms a protective layer the keeps it moistened. This is why first the peel is stained then glycerin is put over.
- State where are the stomata ideally located. Are they cellular structures?
Answer. Stomata are minute pores found on the surface of leaf. Yes they are cellular structures.
- Explain why only turgid leaf is selected for the preparation of a temporary mount of a leaf peel?
Answer. When guard cells are turgid, the stoma remains open and stomatal aperture is easily observable.
- State any two functions of the cells surround the stomata?
Answer. Protective function: Cells protect the inner tissues from external factors, excessive evaporation, attack by pathogen and herbivore animals.
Regulatory function: Specialised epidermal cells called guard cells regulate opening and closing of stomata.
- What is the use of KOH solution in the experiment to show that CO2 is given out during respiration?
Answer. During the experiment, germinating seeds give out CO2 which is absorbed by KOH. Thus a partial vacuum is created in the flask due to which water level rises in the tube.
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