Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
The objects from which light cannot pass through, are called opaque objects. When any opaque object comes in the path of light, then a dark structure is formed called shadow.
Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?
In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot
iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.
(a) Which kind of garbage is not converted into compost by the redworms?
(b) Have you seen any other organism besides redworms, in your pit? If yes, try to find out their names. Draw pictures of these.
To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Do you find that all living beings need the same kind of food?
Name the major nutrients in our food.
Classify the following fibres as natural or synthetic:
nylon, wool, cotton, silk, polyester, jute
Name five objects which can be made from wood.
Why do we need to separate different components of a mixture? Give two examples.
Correct the following statements and rewrite them in your notebook.
(a) Stem absorbs water and minerals from the soil.
(b) Leaves hold the plant upright.
(c) Roots conduct water to the leaves.
(d) The number of petals and sepals in a flower is always equal.
(e) If the sepals of a flower are joined together, its petals are also joined together.
(f) If the petals of a flower are joined together, then the pistil is joined to the petal.
Fill in the blanks:
(a) Joints of the bones help in the ——————— of the body.
(b) A combination of bones and cartilages forms the _______ of the body.
(c) The bones at the elbow are joined by a ______________________ joint.
(d) The contraction of the _____________ pulls the bones during movement.
What is a habitat?
Column I shows different positions in which one pole of a magnet is placed near that of the other. Column II indicates the resulting action between them for each situation. Fill in the blanks.
Column I Column II
N - N _________
N - _________ Attraction
S - N _________
_________ - S Repulstion
Give two examples each, of modes of transport used on land, water and air.
Match the items in Column I with one or more items of Column II.
Column I Column II
Upper jaw have fins on the body
Fish has an outer skeleton
Ribs can fly in the air
Snail is an immovable joint
Cockroach protect the heart
shows very slow movement
have a streamlined body
Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Why can a pace or a footstep not be used as a standard unit of length?
A drawing sheet changes when you draw a picture on it. Can you reverse this change?
How would you obtain clear water from a sample of muddy water?
Explain why the bulb would not glow in the arrangement shown in Fig. 12.13.
Why could you not use an elastic measuring tape to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape?
Give an example of a non-living thing, which shows any two characteristics of living things.