Solutions of practice worksheet 2 (class 7)

 Solutions of practice worksheet 2 (class 7)

1.  Name the acid/base/salt present in the following:

a.       Each cell of our body

Ans. Deoxyribonucleic Acid (DNA)

b.      Window cleaner

Ans. Ammonium hydroxide (Base)

c.       Chalk powder

Ans. Calcium carbonate (Salt)

d.      Spinach

Ans. Oxalic acid

2.   What are the factors on which the amount of heat produced in a circuit depends?

Ans. The amount of heat produced in a circuit depends on its

·         nature of materials used in circuit

·         length of a wire

·         thickness of wire of a wire

·         current passing through circuit

3.   Define :

a.       Spectrum

Ans. Band of colous formed after dispersion of light.

b.      Refraction

Ans. Bending of light when it enters from one medium to another.

4.   Give reasons:

a.       Factory waste is neutralized before disposing it into the water bodies.

Ans. The wastes of many factories contain acids. If they are allowed to flow into the water bodies, the acids will kill fish and other organisms. The factory wastes are, therefore, neutralised by adding basic substances.

b.      Blood of insects does not contain hemoglobin.

Ans. In humans, Hemoglobin binds up with oxygen and helps in carrying oxygen throughout the body.

Insect have a system of tubes (spiracles) that transport gasses directly between their cells and the outside air. Their blood does not carry gasses and has no hemoglobin. 

c.       Dispersal of seeds is necessary.

Ans. 

      • It prevents overcrowding of plants in an area.
      • It prevents competition between the plant and its own seedlings for sunlight, water and minerals.
      • It also enables the plants to invade new habitats for wider distribution.

5.   Calculate the pulse rate if a heart beats 592 times in 8 minutes.

Ans. Each heart beat generates one pulse in arteries

        Number of heart beats = 592

        Time taken = 8 minutes

        Rate of heart beat = 592/8 = 74 beats/min which is equivalent to pulse rate that is 74 pulse/min.

6.   Differentiate between: (Any three)

a.       Artery and Vein



b.      Acid and Base

Basis of difference

Acids

Bases

Taste

Sour

Bitter

Touch

Not slippery or soapy in touch

Slippery or soapy in touch

Role in neutralization

Donate H+ ion

Donate OH- ion

With litmus

Blue litmus changes to red.

Red litmus changes to blue.

c.       Inhalation and Exhalation



d.      Pollination and Fertilization


e.      Mirror and Lens

Mirror

Lens

It is opaque

It is transparent

It works on the principle of reflection

It works on the principle of refraction

f.        Fuse and MCB

Fuse

MCB

Fuse has a simple design and small size.

MCB has a complex design and comparatively larger size.

It has very small operating time.

It has large operating time compared to fuse.

Not expensive.

Expensive device.

Requires replacement of wire after operation.

No replacement is required after operation.

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