class 7 / science worksheet

Ch: 9: SOIL: A NATURAL RESOURCE

Fill in the Blanks

1.      _____________________is the process of breaking down of rocks into smaller particles and forming soil due to long exposure to the atmosphere.

2.      Wind, water and ___________________ are some of the weathering agents.

3.      The process of weathering takes_______________ of years for the formation of soil.

4.      Soil contains____________________ which is formed by the decomposition of dead organic matter mainly from fallen leaves or other plants.

5.      _______________________present in the soil help in breaking down dead matter and converting into humus.

6.      A vertical section of soil, from ground surface to parent rock is called _____________.

7.      The A-horizon, also known as the_____________________ provides shelter to many decomposers such as microbes and worms.

8.      The B-horizon, also known as the  ________________________ is rich in minerals due to deposits of minerals.

9.      The C- horizon or thee parent rock layer is the layer through which ___________ cannot penetrate as it consists of fragments broken down from the bed rock.

10.  The C-horizon layer is also known as the _____________________  .

True or False

1.      The main constituents of the soil are sand and clay -

2.      Particles of clayey soil are easily visible and have gritty structure -

3.      Sandy soil is usually formed from rocks such as limestone, granite and shale -

4.      Sandy soil can hold air, but its water holding capacity is very less and hence such a soil is used not used for growing crops -

5.      Fine air particles in clayey soil increase the water holding capacity of soil but cannot hold air for breathing of plant roots -

6.      Sandy soil naturally forms lumps with water and is hence used for pottery and making bricks -

7.      Loamy soil is gritty as well as smooth -

8.      Sandy soil is considered the best for farming and gardening -

9.      Percolation rate for a given soil is the time taken by water to pass through it -

10.  The ability of the soil to retain water is also called its water absorption ability -

 

Ch: 14: Electric Current and its Effects                                           

Fill in the Blanks

1.      Flow of____________________ through a conducting material is called electric current.

2.      Electric current flows through an uninterrupted path called the __________________.

3.      The three essentials for electric current to flow are ____________________ , _________________ and _________________________ .

4.      A simple electric circuit can be made by using ____________________ , __________________________ and __________________________ .

5.      If we replace the metal wire with a rubber band in electric circuit , the bulb will _____________________.

6.      In a/an _____________________ circuit, current flows uninterrupted.

7.      In a/an __________________ circuit, current does not flow.

Answer in One Word

1.      Source of electric current -

2.      Positive terminal of one cell connected to the positive terminal of the next cell -

3.      Represents a circuit with help of symbols -

4.      Several cells connected together -

5.      Used for measuring potential differences -

6.      Positive terminal of one cell connected to the negative terminal of next cell -

True or false

1.      The energy present in electric current is heat energy -

2.      The heat produced during flow of current depends on the amount of resistance offered by the wire -

3.      Tungsten offers very less resistance to current flowing through it -

4.      An electric fuse consists of a wire made up of steel -

5.      The wire present in electric fuse has a very high melting point -

 
Ch11: Transportation in Animals and Plants

Fill in the Blanks

1.      A _________________________ system is required to expel waste from the body.

2.      Food in plants is transported by _________________.

3.      The blood flows through vessels called _________________.

4.      Arteries carry _____________________ blood from _______________  to different parts of the body.

5.      ________________________ artery  carries deoxygenated blood.

6.      ______________________  helps to cool the plants.

7.      ________________________ are thin walled and superficial blood vessels.

True or False

1.      Blood is an organ -

2.      A white colored pigment called haemoglobin is present in the RCB’s -

3.      Heart is located centrally and tilted towards right -

4.      The valves between auricles and ventricles allow the blood to flow in both directions -

5.      In lungs, the blood gets rid of carbon dioxide and takes in oxygen-

Label the following diagram

CLASS 6 / WORKSHEET

CLASS 7 / worksheet on COMPARING QUANTITIES

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CLASS 10 / EXPERIMENT 5 / REFRACTION THROUGH GLASS SLAB

EXPERIMENT – 5

To study refraction of light in rectangular glass slab

THEORY

• To understand the refraction of light through a glass slab consider the figure given below which shows the refraction of light through a rectangular glass slab.
• Here in this figure AO is the light ray travelling in air and incident on glass slab at point O.
• Now on entering the glass medium this ray bends towards the normal NN’ that is light ray AO gets refracted on entering the glass medium.
• After getting refracted this ray now travels through the glass slab and at point B it comes out of the glass slab as shown in the figure.
• Since ray OB goes from glass medium to air it again gets refracted and bends away from normal N₁N'₁ and goes in direction BC.
• Here AO is the incident ray and BC is the emergent ray and they both are parallel to each other and OB is the refracted ray.
• Emergent ray is parallel to incident ray because the extent of bending of the ray of light at the opposite parallel faces which are PQ (air-glass interface) and SR (glass-air interface) of the rectangular glass slab is equal and opposite.
• In the figure i is the angle of incidence, r is the angle of refraction and e is the angle of emergence.
• Angle of incidence and angle of emergence are equal as emergent ray and incident ray are parallel to each other.
• When a light ray is incident normally to the interface of two media then there is no bending of light ray and it goes straight through the medium.

APPARATUS:

A drawing board, rectangular glass slab, office pins, sheet of white paper, a protractor and sharply pointed pencil.

PROCEDURE:

1. Fix a sheet of white paper on a drawing board with drawing pins. Place the given glass slab nearly in the middle of the sheet.
2. Mark the boundary of the glass slab with a sharp pencil and label it as PQRS after removing the slab from its position.
3. On the line PQ mark a point E and draw a normal N1EN2 at it. Draw a line AE making angle AEN1 with the normal.The angle should neither too small nor too large (say about 40 degree).
4. Now place the glass slab again on its boundary PQRS and fix two pins A and B vertically about 10 cm apart on the line AE (say points A and B).
5. Look through the glass slab along the plane of the paper from the side SR and move your head until the images of the two pins A and B are seen clearly. Closing your one eye ,adjust the position of your head in such a way that the images of the pins A and B lie in the same straight line.
6. Fix two other pins C and D vertically in such a way that the images of the pins A and B and pins C and D, all these four, lie in the same straight line. Ensure that the feet of the pins ( not their heads ) lie in the same straight line.
7. Remove the slab and also the pins from the board and encircle the pin-pricks on the paper,with a sharp pencil.
8. Join the points D and C and produce the line DC towards the slab so that it meets the boundary line RS at the point F. Join the points e and F. Thus for the incident ray represented by line AE, the refracted ray and the emergant ray are represented by EF and FD respectively.
9. On the line RS draw a normal N1'FN2'  at point F. Now, with a protractor, measure angle AEN1, angle FEN2 and angle DFN2' labelled as angle i, angle r and angle e respectively. 
10. Now place the glass slab at some other position on the sheet of paper fixed on the board and repeat all the above steps again taking another angle of incidence.
11. Measure the angle of incidence i.e angle of refraction, angle of emergence, again.

 

 RESULT:

1) Within the experimental error, ∠i = ∠e. It implies incident ray and emergent ray are parallel to each other

2) ∠i > ∠r. it means a ray of light while passing from air to glass bends towards normal.