Monday 27 February 2017

 REVISION WORKSHEET
CLASS 6-BODY MOVEMENTS

Exercises
1. 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.


2. Indicate true (T) and false (F) among the following sentences.
(a) The movement and locomotion of all animals is exactly the same. ( )
(b) The cartilages are harder than bones. ( )
(c) The finger bones do not have joints. ( )
(d) The fore arm has two bones. ( )
(e) Cockroaches have an outer skeleton. ( )



3. Match the items in Column I with one or more items of Column II.
Column IColumn II
Upper jawhave fins on the body.
Fishhas an outer skeleton.
Ribscan fly in the air.
Snailis an immovable joint.
Cockroach             protect the heart.
-shows very slow movement.
-have a streamlined body.


4. Answer the following:
(a) What is a ball and socket joint?
(b) Which of the skull bones are movable?
(c) Why can our elbow not move backwards?
CLASS 6
MOTION AND MEASUREMENT

1. Fill in the blanks:
(i) One metre is ______________ cm.
(ii) Five kilometre is ______________ m.
(iii)Motion of a child on a swing is ______________.
(iv)Motion of the needle of a sewing machine is ______________.
(v) Motion of wheel of a bicycle is______________.

Answer

(i) One metre is 100 cm.
(ii) Five kilometre is 5000 m.
(iii)Motion of a child on a swing is periodic motion.
(iv)Motion of the needle of a sewing machine is periodic motion.
(v) Motion of wheel of a bicycle is circular motion.

2. Why can a pace or a footstep not be used as a standard unit of length?

Answer

The length of pace or a footstep varies from person to person. If the length of footstep will be used as standard unit for measurement of length then two measured quantity will not be same. Hence, footstep or pace is not a constant quantity and cannot be used as a standard unit of length.

3. Arrange the following lengths in their increasing magnitude:
   1 metre, 1 centimetre, 1 kilometre,1 millimetre.

Answer

1 millimetre > 1 centimetre > 1 metre > 1 kilometre

4. The height of a person is 1.65 m. Express it into cm and mm.

Answer

1.65 m = 1.65 × 100 cm  = 165 cm
1.65 m = 1.65 × 100 × 10 mm  = 1650 mm

6. The distance between Radha's home and her school is 3250 m. Express this distance into km.

Answer

1km = 1000 m
3250 m = 3250/1000 km = 3.25 km

5. While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?

Answer

The actual count of the length of the needle start from 3.0 cm instead of 0 cm. Thus, the actual length of the needle is (33.1 - 3.0) cm = 30.1 cm

6. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.

Answer

Similarities:
(i) Both the ceiling fan and the wheels of a bicycle show circular motion.
(ii) Both are fixed at point.
Differences:
(i) A bicycle shows rectlinear motion while a ceiling fan does not.

7. 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?

Answer

An elastic tape is flexible and can be stretched. Thus, each time it will give different readings for the same length measured. Therefore, it is impossible to measure accurate distance from an elastic measuring tape.

8. Give two examples of periodic motion.

Answer

Two examples of periodic motion:
(i) Motion of a pendulum clock.
(ii) Motion of a swing.
class 8 revision worksheet
CHEMICAL EFFECTS OF ELECTRIC CURRENT

1. Fill in the blanks.
(a) Most liquids that conduct electricity are solutions of ________, _______ and ________.
(b) The passage of an electric current through a solution causes _________ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the __________ terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called _________.

Answer

(a) Most liquids that conduct electricity are solutions of acidsbases and salts.
(b) The passage of an electric current through a solution causes chemical effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.

2. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

Answer

Electric current produces magnetic effect which causes deflection of the magnetic needle of a compass. So, when the free ends of a tester are dipped into a solution which is a good conductor of electricity, the needle shows deflection.

3. Name three liquids, which when tested in the manner shown in Fig. 14.9, may cause the magnetic needle to deflect.
Fig 14.9

Answer

Liquids like lemon juice, salt water and vegetable oil allow electricity to pass through them. Hence, these liquids can be used as in the beaker to show the given effect.

Page No: 181

4. The bulb does not glow in the setup shown in Fig. 14.10. List the possible reasons. Explain your answer.

Answer

There could be several possible reasons for not glowing of the bulb:
→ The bulb may be fused.
→ Even after replacing the bulb if it does not glow, then the connection may be loose or faulty.
→ Even after checking and repairing the connections if the bulb does not glow that means the solution does not conduct electricity.

5. A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that
(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.
► (i) liquid A is a better conductor than liquid B.

6. Does pure water conduct electricity? If not, what can we do to make it conducting?

Answer

No. Pure water does not conduct electricity. Pure water can conduct electricity when a pinch of common salt is added to it, as salt solution is conducting in nature.

7. In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.

Answer

Water may conduct electricity. If the electrical supply for the area is not shut off and water is poured over electrical appliances, then electricity may pass through water and harm the firemen. That is why, in case of a fire, the firemen shut off the main electrical supply for the area before they use the water hoses.

8. A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?

Answer

Sea water contains more dissolved salts than the drinking water. Hence, it is more conducting than the drinking water. Because of this reason, the compass needle deflects more in seawater than in the drinking water.

9. Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.

Answer

No, it is very risky and unsafe for the electrician to carry out electrical repairs outdoors during heavy downpour because rain water contains dissolved salts. Therefore, rain water can conduct electricity. The electrician may get electrical shocks while working outdoors during rain.

10. Paheli had heard that rain water is as good as distilled water. So, she collected some rain water in a clean glass tumbler and tested it using a tester. To her surprise, she found that the compass needle showed deflection. What could be the reasons?

Answer

Rain water contains dissolved salts. This makes it a conducting solution. There are no dissolved salts present in the distilled water. Hence, rain water can allow electricity to pass through it while distilled water cannot.

11. Prepare a list of objects around you that are electroplated.

Answer

→ Cars bumpers and cycles handles are chromium plated to give them shiny appearance.
→ Artificial jewellery items are gold or silver plated.
→ Iron used in constructing a building is coated with a layer of zinc to protect it from rusting.

12. The process that you saw in Activity 14.7 is used for purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?

Answer

Copper ion is positively charged. It is attracted towards the plate which is connected to the negative terminal of the battery. As copper ions are transferred to the thin copper plate, this thin pure copper plate must be connected to the negative terminal of the battery. Consequently, impure copper rod is connected to the positive terminal of the battery.
Revision worksheet-class 7
MATTER AND CHEMICAL FORMULAE

1 Write the chemical formulae of the following compounds
a. Copper sulphate
b. Sodium nitrate
c.Carbon-di-oxide
d. Ammonium Sulphate
e. Magnesium hydroxide.

2.Differenciate between atoms and molecules.
3.Define ores.Give any two examples
4.Can you separate the constituents of Fes( Iron sulphide) using a magnet? Give reason.
5.Give symbols of
Copper, Silver, Mercury, Gold,Iron Silicon, Aluminium, Chlorine
6. Write the atomicity of
Phosphorus, Nitrogen, Helium ,Ozone,Sulphur, Sodium
7Give reasons-
- Is copper an element
-water is acompound.
-Air is a mixture .
8.Name the elements present in Al2O3.Also write the valencies.
-


Thursday 23 February 2017

CLASS 6
REVISION WORKSHEET -LIGHT ,SHADOW AND REFLECTION

Which of the following is a false?
(a) All objects cast shadows.
(b) Mirror changes direction of light that falls on it
(c) image in a plane mirror is of the same size and colour as that of the object.
(d) Coloured objects form coloured shadows
(e) The phenomenon of bouncing back of light after falling on the surfaces of the objects is called reflection of light.
Question 2
 What is true about reflection from plane mirror?
(a) The image formed by plane mirror is erect and virtual.
(b) Size of the image formed by plane mirror is equal to the size of the object.
 (c) The distance of the image behind the plane mirror is equal to the distance of the object from the mirror
(d) All the above

Question 3
Which of the following is sources of artificial light?
(a) electric bulb
(b) Candle
(c)  Torch
(d) All the above

Question 4
What is lateral inversion?
(a) Image looks shorter in size
(b) Image looks larger in size
(c) The right side of the object appears to be the left side of its image and vice-versa
(d) None of the above

Question 5
Two statement are given
Statement A: We cannot see our image in the mirror in complete dark room because there is no light to reflect.
Statement B: We cannot see objects through T shaped pipe because light travels through straight line

(a) Statement A is correct only
(b) Statement A is correct only
(c) Statement A and B both are incorrect
 (d) Statement A and B both are correct
 
Long Answer type questions
Question 6
Distinguish between
a) transparent, translucent and opaque materials?
b) Luminous and Non Luminous objects
Question 7
Moon appears bright at night. Is it a luminous or non-luminous body?
Question 8
Explain how we see our image in the Mirror?
multiple choice questions

1. Stars are
a. Non luminous bodies
b. Luminous bodies
c. Artificial sources of light
d. Opaque bodies
2. Moons and planets
a. Radiate light energy
b. Reflect light energy
c. Absorb light energy
d. Split light energy

3. Rectilinear propagation of light means
a. Light travels in straight lines
b. Light travels in curved path
c. Light travels in zig-zag path
d. Light travels in circular path

4  The speed of light is
a. 300,000 km/s.
b. 300,000 m/s
c. 30,000 km/s
d. 30, 000 m/s
5. The light from the sun reaches the earth in
a. 8.33 minutes
b. 8.33 seconds
c. 18. 33 minutes
d. 88.33 seconds
6. A body which emits light by itself is
a. Luminous body
b. Non luminous body
c. Opaque body
d. Shadow

7. The size of a shadow of an opaque object close to the screen and away from the source of light
a. Increases
b. Decreases
c. Remains the same
d. First decreases and increases.
8. This takes place from smooth polished surface when a beam of light falls on it
a. Reflection
b. Absorption
c. Refraction
d. Radiation
9. The image formed in pinhole camera is
a. Inverted
b. Erect
c. None of these
d. Both a and b
10. A dark patch formed by an opaque body placed in the path of light is called
a. Image
b. Object
c. Shadow
d. Screen
11. Reflection does not takes place from a
a. Polished metal plate
b. Mirror
c. Undisturbed water
d. Book