CBSE Class 9 Science Sample Paper with Answers Set 21

SECTION-A

1. Name the state of matter which consists of super energetic and super excited particles in the form of an ionised gas.

Ans. Plasma

2. Write the ways in which insect pests attack plants.

Ans. Insect pests damage/harm the plants in the following ways :

       (i) They cut root, stem and leaf.

       (ii) They suck the cell sap from various plant parts.

       (iii) They bore into stems and fruits.

       (iv) They form galls.

       (v) They eat stored grains.

3. How does carbon dioxide or oxygen move across the cell membrane?

Ans. Cell membrane is selectively permeable for certain molecules to pass through it.

4. Define plasmolysis. How does it occur?

Ans. The phenomenon of the loss of water from a plant cell by osmosis, so that the cytoplasm shrinks away from the cell wall is called plasmolysis. It occurs when a cell is kept in a hypertonic solution.

5. How can you distinguish between a salt solution and a pure liquid without tasting it?

Ans. On evaporation, a salt solution will leave a residue of salt, when all the liquid evaporates. A pure liquid leaves no residue on evaporation.

6. Why is epidermis important for plant?

Ans. Epidermis is important for plants because :

        (i) it protects plant body from desiccation and infection.

        (ii) cuticle of epidermis cuts the rate of transpiration and prevents them from wilting.

        (iii) stomata in epidermis allow gaseous exchange.

7. A bar of gold is found to have a mass of 100 g and weight of 0.98 N at some place. When the bar is taken to some place at the equator, it is found that the mass remains 100 g, but the weight is less than 0.98 N. Explain the above observations.

Ans. (i) The mass of the gold bar is a constant quantity, and hence, will remain same anywhere and everywhere.

      (ii) The weight of the gold bar decreases because the acceleration due to gravity is least at the equator. As weight is the product of mass and acceleration due to gravity, therefore, its value decreases at the equator.

8. What is a colloidal solution? How is it different from a true solution? Identify the colloidal solutions from the following : Copper sulphate solution, vinegar, blue ink, milk of magnesia.

Ans. A heterogeneous solution in which particle size is between 10^–7 cm to 10^–5 cm in diameter, such that the solute particles neither dissolve nor settle down in a solvent, is called a colloidal solution. But true  solution is a homogeneous solution in which particles cannot be seen under a microscope. Milk of magnesia is a colloidal solution.

9. Write one function each of the following : 

    (a) Tendon (b) Ligament (c) Areolar tissue

Ans. (a) Tendons connect muscles to bones.

        (b) Ligaments connect one bone to another bone.

        (c) Areolar tissue binds the skin with underlying parts.

10. How are the following transported into and out of the cell? Explain.

     (a) water (b) carbon dioxide in plants

     (c) food particles in amoeba

Ans. (a) Movement of water molecules occurs due to osmosis. Concentration of water depends on the dissolved materials present in it. Here, water moves through a selectively permeable membrane from lower concentration to higher concentration of solution.

       (b) Movement of CO₂ in and out of the cell occurs through diffusion. When concentration of CO₂ is higher inside the cell in comparison to the cell’s external environment, then this difference in concentration of CO₂ in and out of the cell leads to diffusion. Thus, CO₂ moves out of the cell from a region of its higher concentration to a region of its lower concentration outside the cell.

        (c) With the help of pseudopodia, Amoeba engulfs food and it is enclosed within the food vacuole from where it takes its nourishment.