Which of the following decreases the rate of evaporation?

Which of the following properties is not characteristic of colloidal particles?

Which one of the following compound is not made up of charged ions?

which one is not true of two isotopes?

Ribosomes are the centre for

A group of cells similar in form, function and origin is known as

Whittaker classified all organisms into

A car increases its speed from 20 km/h to 50 km/h in 10 seconds .Its acceleration is

The combined effect of mass and velocity is taken into account by a physical quantity called

At which of the following locations, the value of g is the largest?

A load is carried through a distance of 5m in the following different ways.In which case the work done is minimum?

If the distance between a crest and its consecutive trough is L, then the wavelength of the wave is given by

What do that following observations indicate?
(i) Headache
(ii) Loose motion
(iii) Cough
(iv) Symptoms of a disease

Nitrogen-fixing bacteria are found in the roots of 

Which one of the following sets of plants includes weeds only?

How do you differentiate between solids, liquids and gases on the basis of their melting points and boiling points?

Sidak took 50 mL water in two beakers at room temperature and added sodium chloride to one beaker while sugar to the other, till no more solute would be dissolved. Then she heated the contents of the beakers and added more solutes in them.
(a) Will the amount of salt and sugar that can be dissolved in water at given temperature same?
(b) What will you expect to happen if she cools the contents of the beakers?justify your answer.

What is meant by the term chemical formula?

Who discovered neutrons?What observation lead to the discovery of neutrons?

Write functions of the
(i) Inner membrane of mitochondria.
(ii) Nucleus of the cell.
(iii) Ribosomes present in active cells.

Blood is a fluid connecting tissue.It is about 5-6 litres in our body. Excessive loss of blood from the body, for any reason, may cause serious consequences.A student got minor cuts while working in science laboratory. The blood was oozing out of the cut. He started crying. His friends took him to the teacher.The teacher asked him to remain calm and keep his emotions and stress under check.The teacher washed the cut with soap and clean water. Then cleaned with Savlon / Dettol soaked cotton. Applied Betadine ointment, dressed with a clean gauze and bandage.
On the basis of above information answer the following questions:
(i) Why the teacher cleaned the cut with Savlon or Dettol soaked cotton?
(ii) If Betadine ointment or any other such ointment is not available, what will you do?
(iii) What key message the teacher conveyed?

What do you mean by 'characteristics'? Explain with example.

Measure the time ti takes you to walk from your house to your bus stop or the school. If you consider that your average walking speed is 4 km\(h^{ -1 }\) estimate the distance of the bus stop or school from your house.

It is dangerous to jump out of a moving bus. Why?

There are four balls A, B, C and D which displace 10 mL, 24 mL, 15 mL and 12 mL of a liquid respectively, when immersed completely. Which ball will undergo the maximum apparent loss in weight?

If the work done by a force in moving an object through a distance of 40 cm is 48.4J, what is the magnitude of the force ?

What is reverberation? How can it be reduced?

(i) Many municipal corporations are trying water harvesting to improve the availability of water. Give reason.
(ii) Rainwater sometimes contains traces of acid. Why? Explain in brief.

What are macro and micro-nutrients of Plants? Name two of each kind.

Nature is complete but very systematic.There is a system which is exhibited by all types of creations and happenings or even human behaviour.That is the phase of transition.This is a so-called equilibrium state.At this stage both the phases are manifested and with a little energy change in any form, either of the two states can be achieved.Natural phenomena though may not be controlled by human power.
Give an account of such equilibrium states when we study states of matter.

How do you establish that air is a mixture and not a pure substance?

Calculate the mass of 0.5 mole of oxygen atoms

The half-life period of Actinium is 15 seconds.Starting with 0.1g of Actinium, how much would be left at the end of one minute?

Describe the role played by the Lysosomes. Why are these termed as suicidal bags? How do they perform their function?

What is the difference between ligament and tendon?

(a) State two characteristic features of nematodes.
(b) Identify the phylum with the help of following features:
(i) Spiny-skinned, radial symmetrical and have tube feet.
(ii) Triploblastic worm-like, having segmented body.

You must have the story of the hare and tortoise. The two started simultaneously from the same point for a common destination. The hare slept for sometime along the way, and the tortoise reached the destination first. Since in this journey the tortoise took less time than the hare, the average speed of the tortoise was greater than that of the hare. But everyone knows that when the hare was actually running, it was much faster than the tortoise.
(a) Define the term speed.
(b) What is the S.I. unit of speed?
(c) Define average speed.
(d) Can the average speed of an object be negative?

A motorcar of mass 1,200 kg is moving along a straight line with velocity of 90 km/h. Its velocity is slowed down to 18 km.h s by an unbalanced external force. Calculate the acceleration and change in momentum. Also, calculate the magnitude of the force required.

A firecracker is fired and it rises to a height of 1000 m. Find the
(i) velocity by which it was released.
(ii) time taken by it to reach the highest point. (Take, g = 9.8 m/s²)

Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term 'work':
(i) Suma is swimming in a pond.
(ii) A donkey is carrying a load on its back.
(iii) A wind-mill is lifting water from a well.
(iv) A green plant is carrying out photosynthesis.
(v) An engine is pulling a train.
(vi) Food grains are getting dried in the sun.
(vii) A sailboat is moving due to wind energy.

What does SONAR stands for?Using Sonar, sound pulses are emitted at the surface.The pulses after reflected from bottom are detected.If the time interval from the emission to the detection of the sound pulse is 2.6 seconds, find the depth of water.

Rohit told Mohit that malaria is spreading these days.you should be careful.Mohit said that he read in the book that malaria is transmitted by the bite of female Anopheles mosquitoes These mosquitoes breed in stagnant water such as ponds,ditches,water coolers,water storage tanks,etc.Rohit and Mohit decided to take help from friends and also take help from concerned Municipal department to do the needful and educate the community.
Answer the following questions based on the above information:
(a) Which preventive measures do you suggest for the prevention of such diseases caused by mosquitoes?
(b) Which values are displayed by Rohit and Mohit?

Discuss the consequences of the increase in the concentration of carbon dioxide in the atmosphere.

Explain the objectives of mixed cropping. How are crops selected for mixed cropping?

Give reasons:
(a) Naphthalene balls disappear with time without leaving any solid.
(b) A gas exerts pressure on the walls of the container.

How are colloidal, solution and suspension different from each other?

Give the chemical name, chemical formulae for the following compounds.
Banking soda, washing soda, blue vitriol, green vitriol, gypsum, oil of vitriol or white vitriol, soda ash, marble chips, lime water.

What the help of Table 4.1, find out the mass number of oxygen and sulphur atom.

Water forms two-thirds of the weight of the body. Body cells contain about 60% to 70% of water.All life processes carried out in a cell require water medium.It is essential to well being, deprivation or loss of water, as in case of diaohrrea, dysentry, vomiting etc. is more immediately serious than of any other article in diet.On the basis of above information answer the following questions:
(i) What first aid you will provide to a patient who has lost sufficient water from the body cells due to loose motions?
(ii) How would you prepare the solution to hydrate the body cells of the patient?
(iii) What would you do for the community with this information?

What is the specific function of the cardiac muscle?

What are the three differences between plants and animals?

What are the uses of graphical study of motion?

State Newton's first law of motion. Explain it with the help of suitable examples.

A stone is dropped from the adge ofg the roof, find
(i) How long does it take to fall 4.9 m?
(ii) How fast does it move at the end of that fall?
(iii) How fast does it move at the end of 7.9 metres?
(iv) What is its acceleration after 1 s and after 2s?

A person holds a bundle of hay over his head for 30 minutes and get tried.Has he done some work or not?Justify your answer.

What is an echo? Give the conditions for the production of an echo.

Give cause and remedy of
(a) Hepatitis (b) AIDS (C) Malaria

You know that the ozone layer of staratosphere of atmosphere protect us from ultraviolet radiations coming from the sun.Ozone layer is decreasing Scientist when talk about ozone 'hole' it means ozone layer at certain area has become very thin. Depletion of ozone layer is worldwide problem. Read more about ozone layer and its protection.
Answer the following questions based on the above information:
(a) On what three precautions/methods you will stress upon while organizing canpaign for creating awareness amongst masses?
(b) Which values are displayed by the students?

Describe the factors responsible for grain loss during storage. Discuss the various measures for safe storage of grain.

Define the following terms:
(a) Latent heat of fusion
(b) Melting point
(c) Fusion
(d) Latent heat of transpiration
(e) Boiling point

(a) name the technique used to separate oil from water and also the principle involved in their separation.
(b) State what are saturated solutions.
(c) To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K.Find its concentration at this temperature.

Define Avogadro's constant and molar mass.How are they related to one mole of an atom, molecule, or ion?

Describe the role played by the lysosomes in the cell. Why are these termed as suicidal bags? How do they perform their function?

An object is moving along a straight line with uniform acceleration.The following table gives the velocity of the object at various instants of time:

Plot the v-t graph From the graph:
(i) Find the velocity of the object at the end of 2.5 seconds.
(ii) Calculate the acceleration.
(iii) Calculate the distance covered in the last 4 seconds.

(i) A person weighs 110.84 N on the moon, whose acceleration due to gravity is 1/6 of that the earth. If the value of g on the earth is 9.8 m/s², then calculate
(a) g on the moon
(b) mass of person on the moon
(c) weight of person on the earth
(ii) How does the value of g on the earth is related to the mass of the earth and its radius? Derive it.
 

(a) Name the commercial unit of electrical energy.
(b) Establish the relationship between the SI unit and the commercial unit of electrical energy.
(c) Calculate the electricity bill amount for a month of 30 days, if 4 bulbs of 50 W for 6 hours, 3 tube lights of 40 W for 8 hours, a T.V. of 100 W for 6 hours, a refrigerator of 300 W for 24 hours are used.The cost per unit is Rs.2.50.