An agricultural implement used since ancient times for tilling the soil, adding fertilizers, removing weeds etc. is :

Which of these does not prevent growth of bacteria?

The most suitable material for the preparation of handles of cooking utensils is

Materials which can be drawn into wires are called ductile. Which of the following is not a ductile material?

Which substance is formed by the carbonisation of dead vegetation?

The calorific value of a fuel is expressed in a unit called

The place of living of an organism in environment is called

Choose the correct statements.

In human beings, the correct sequence of events during reproduction is

The number of chromosomes are present in human cell

The pressure exerted by liquid due to increase in depth

The force of friction always

The loudness of sound is determined by its

Which of the following metals is used in electroplating to make objects appear shining?

Which of the following can be charged with static electricity?

Two mirrors A and B are placed at right angles to each other as shown in Fig. below:
 
A ray of light incident on mirror A at an angle of 25° falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be:

Which star is nearest to the Earth?

Biological pollution in water is caused by

Is there any advantage of using a cultivator?

In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?

Name the first and most popular synthetic fabric

Name a non-metal which is kept in water

Which product of coal is used as a reducing agent in the extraction of metals?

If you burn a candle and coal, what is the difference in their burning?

Write any two consequences of deforestation.

A part of the cell gives shape to it. Give its name

Give another term for a fertilised egg.

What makes the fertilized egg develop either into a boy or a girl?

We do not feel atmospheric pressure on our body. Explain the reason in brief.

Why it is difficult to move on a wet marble floor?

How does the sound travel?

Name some substances which make a liquid good conductor of electricity.

If an object is touched with the metal top of an electroscope its aluminium leaves diverge then what conclusion we get from this observation?

A banana appears yellow. Why?

What do you mean by constellation? Name any two.

Run-off water from a garden is not considered a point source of pollution. Give reason.

Differentiate between Fertilizer and Manure.

What is the importance of immunization in eradicating diseases from a country?

Write disadvantages of plastics.

One day Reeta went to a jeweller's shop with her mother. Her mother gave an old jewellery to the goldsmith to polish. Next day, when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

Explain why fossil fuels are exhaustible natural resources.

Once in a village, there was a fire in a hut. When a lot of dry powder of a substance, A is released over a fire, the fire gets extinguished.
(a) Name the substance A.
(b) How does the substance extinguish the fire?
(c) Give one another substance which behaves like substance A.

Some tribals depend on the jungle. How?

A cell of a neem tree contains part A and B that are not present in a human. Part A contains a pigment C that gives green colour to its leaves. Part B gives shape and support to the cell and is made of D.
(a) What is A and B?
(b) Can you identify C and D?
(c) Write functions of A and C.

Explain the structure of a sperm.

Define adolescence.

In the following situation, identify the agent exerting the force and the object on which it acts. State the effect of the force in each case.
(a) Squeezing a piece of lemon between the fingers to extract its juice.
(b) Taking out paste from a toothpaste tube.
(c) A load suspended from a spring while its other end is on a hook fixed to a wall.
(d) An athlete making a high jump to clear the bar at a certain height.

What is the cause of friction?

Briefly explain total hearing impairment.

Explain in brief the procedure of glowing of bulb in a liquid

Explain how do the buildings can be designed and constructed in seismic zones.

Write the structure and function of human eye.

Mention about the shifting of the Sun towards the south and towards the north

We can survive for sometime without air but we cannot survive even for a few minutes without food.

Paddy is a major cereal crop in our country.
(a) In which season is paddy cultivated?
(b) Discuss the method of sowing.
(c) What measures must be taken to prevent spoilage and insect attack of harvested grains?

Write a short paragraph on the diseases caused by micro-organisms.

Karan, a student of class VIII carelessly throw polybags here and there. Sometimes he throw the wrappers of chips, biscuits and other eatables on the road or in park or in his house. Karan's mother was very upset she told him not to throw things carelessly. She advised him to keep your home, school and public places clean. So, your younger brother will also learn the same thing. Karan followed her mother advice.
Read the following passage and answer the following questions.
(a) What is the harmful effects of throwing polybags or wrappers of food on public places.
(b) What are 4 R principle that are should follow to keep their environment clean?
(c) What values are shown by Karan?

Iron is more reactive than copper. Can you write an activity to show this?

The material X is a fossil fuel. It is formed from the buried large land plants (vegetation) by a very slow process Y. When X is heated in the absence of air, i. e. in the process called Z, it gives three products A, B and C. A is used as a reducing agent in the extraction of metals, B is used as an industrial fuel, whereas the product C has been traditionally used for metalling the roads. It is now replaced by a petroleum product, bitumen. Now give the answer of the following questions.
(a) What is the material X?
(b) What is the physical state and colour of X?
(c) Name the processes Y and Z.
(d) What are the products A, B and C?

Although wood has a very high calorific value, we still discourage its use as a fuel. Explain.

During an educational trip to a renowned forest, Amit saw a highway being constructed which passes through the middle of the forest. He was unhappy seeing that and contacted the wildlife department to stop the work.
(i) If the highway is constructed what would be the effect?
(ii) Forests are useful to mankind. Comment.
(iii) Give the values of Amit shown here.

What is a gene? What are its functions?

What are clones? What are the various steps of this process? Explain with examples.

It is believed that height of a child depends upon the genes inherited from parents. However, it is often seen that tall parents may have short children and vice-versa. Are these factors other than genes that can cause these variations?

In physics class teacher ask to his student that a man carrying a load of 50 N in his hand pulling it. The area of palm where the load act is 5 cm². Then
(a) Determine the pressure acting on the fingers of man.
(b) Also, find the pressure acting if the man carrying the same load by keeping it on the shoulder occupying an area of 50 cm².
(c) Mention the type of teaching skill of teacher is being represented here?

Name the factors that affect friction.

Explain in detail how sound travel slower than light.

What is electroplating? What are its advantages?

If the metal clip used in the electroscope is replaced by an ebonite rod and a charged body is brought in contact with it, will there be any effect on the aluminium strips? Explain.

How is the phenomenon of reflection used in making a kaleidoscope? What are the applications of a kaleidoscope?

Figure shows comets without their tail. Show the tails of the comets at positions A, B, and C. In which position will the tail be longest?

It is said, "C0₂ contributes to global warming". Explain