List of top Science Questions asked in CBSE Class X

Mention any one harmful effect of using plastic bags on the environment. Suggest better alternatives to the usage of plastic bags.

Given below is a diagrammatic representation of cross-section of a leaf: 

Identify ‘P’ in the given diagram and write down its role in plants. Write down a balanced equation of process of photo-synthesis.

Which of the plant hormones are responsible for the following processes? Promote cell division Inhibition of growth Detection of light Wilting of leaves

Observe the given figure and identify the labelled parts P, Q, R and S.

Assertion : Bacteria produced as a result of asexual reproduction would be similar. Reason (R): There would be only minor differences between the bacteria generated due to small inaccuracies in DNA replication.
Assertion : The peristaltic movements occur all along the gut. Reason (R): The lining of the gut has muscles that contract rhythmically to push the food in regulated manner.
When a human egg is fertilized by a sperm having ‘Y’ chromosome, the zygote has the following combination of chromosomes:
Which of the following is a non-biodegradable pollutant?
Choose the equation of reaction that correctly represents anaerobic respiration in muscles:
Identify the part that controls the closing and opening of the stomatal pore in leaves of plants. Select the correct option.
Yeast multiplies by which of the following methods?
State Joule's law of heating.
Name the device used for measuring electric current. How is it connected in a circuit ?
How many bulbs of resistance \( 8 \ \Omega \) each should be connected in parallel combination to draw a current of \( 2 \text{ A} \) from a battery of \( 4 \text{ V} \) ?
Define the S.I. unit of electric current.
Conductors of electric toasters and electric iron are made of an alloy rather than a pure metal. Why ?
Due to change in length and area of cross-section of a conductor, resistance of conductor changes while resistivity does not change. Why ?
A person is unable to read a book placed closer than \( 1 \text{ meter} \) from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.
Write the preparation of following compounds with balanced chemical equation :
Baking soda
Bleaching powder
Plaster of Paris
Explain chlor-alkali process with chemical equation. Name the products formed at anode and cathode.
Give one example each of electrolytic decomposition and decomposition by sunlight.
Balance the following chemical reaction: \( Pb(NO_3)_2 + KI \longrightarrow PbI_2 + KNO_3 \)
Name the substance oxidised and reduced in the following reaction: \( ZnO + C \longrightarrow Zn + CO \)
Categorise the following based on their nature: \( ZnO, Na_2O, CO_2 \)
What are amphoteric oxides?