Explore topic-wise InterviewSolutions in Current Affairs.

1. These spherical parts are known as concave and convex parts.

2. A spherical mirror in which the outwardly curved part works as reflector is called Convex Mirror.

3. A spherical mirror in which the bulged inward part i.e. the center of the spherical mirror work as reflector is called Concave mirror.

1. Virtual

2. 0° 

3. Concave

(b) concave mirror

(i) Industries cause pollution by loading chemical effluents and makes the water toxic, killing aquatic organisms, and is harmful for people. 

(ii) (a) Drainage of household sewage into rivers. 

(b) Washing clothes and flowing pesticides into water. 

(iii) (a) They organise a camp to tell people about water conservation. 

(b) They tell people about rainwater harvesting.

(i) Improvement in our life style has led to use of more of electronic gadgets like computers, laptops, mobile phones etc. 

The companies in order to increase their sales keep on launching new upgraded versions which attract the buyers and increase the waste. 

(ii) Think about the utility and then only buy the upgraded models not just because friends are having so I should also buy it. 

Try to reuse the old TV, computers, mobile phones or other electronic gadgets if it is in working condition by selling/giving it to the needy. 

(iii) Concern towards the society, environment friendly.

Correct option is a. BF₃

BF₃ is non polar because it has trigonal planar geometry and the dipole moments of individual B-F bonds cancel each other.

Correct option is c. H₂O₂

Wildlife- All naturally occurring plants, animals and their species which are not cultivated/ domesticated/ trained.

Importance:

(i) Help in maintaining ecological balance.

(ii) Provide great aesthetic value for human beings.

(iii) They have economical importance also.

Sustainable development : Development which meets the current basic human needs, while preserving the resources for the needs oi future generation. 

It is necessary for environment conservation.

Advantages:
(i) Provides the resources for the present generation.
(ii) Preserves the resources for the future generation as well
Reuse is better than recycling because it does not involve use of energy.

occupy the entire space of the container.

A substance which can change its state oxygen.

occupy space and have definite mass

The process by which a solid change into a liquid is called melting.

A kind of matter which can sublime is iodine.

they can flow is a property of the liquids.

The state of matter which has no definite shape or volume is called gas.

(a) Particles move about very quickly Liquid

(b) Particles are quite close together Solid

(c) Particles are far apart and move in all directions Gas

(a) Substances which sublime.

Naphthalene, camphor, dry ice.

(b) Substances which do not change their states.

Paper, sugar.

(c) Substances which are rigid and not compressible.

Glass, stone, pen.

There are large intermolecular gaps in air.

petroleum is a kind of matter.

(a) True

(b) True

(c) False

(d) False

(e) False

(f) True

(g) True

(h) False.

As a liquid is heated, its particles start gaining energy and move more vigorously which increases the gaps between the particles and decreasing the force of attraction. Ultimately a liquid changes into a gaseous state.

(a) False. 

correct: Matter can exist in different states.

(b) True.

(c) False. 

correct: Gases and liquids can flow.

(d) False. 

correct: Solids cannot be compressed easily.

(e) True

(f) False. 

correct: The intermolecular space in a gas is very large.

1. Water is a matter because it has mas and occupies space.

2. Any matter which has a definite volume but no definite shape is called a liquid.

3. Fluid can flow.

4. The molecules are at a greater distance in gases compared to liquids.

5. Water boils at 100 °C.

6. The physical state of a substance, which has a fixed volume but no fixed shape is liquid.

7. All matter is made up of tiny particles called atoms.

8. Liquids have a definite Volume.

9. The temperature at which a liquid boils is called the boiling point of that liquids

10.Molecules in a solid are packed very closely.

11.Liquids have no definite shape.

12.When a gas is cooled, its molecules loose energy,

13.Matter is anything that has mass and occupies space.

Take a completely filled glass of water. Add a spoon full of sugar. Stir it well. The volume of water hence the level of water in glass remains the same where has gone the volume of sugar added? Actually, the sugar molecules took the spaces (gaps) between the molecules of water and the level of water in glass remains the same. This shows that there are intermolecular spaces between the water molecules.

(a) When a teaspoon of sugar is added to half a glass of water and stirred, the water level in the glass does not rise. 

Add one teaspoon of sugar to it and stir. The sugar disappears but the level of water in the glass does not rise that means the volume of water has not increased. Because the sugar particles are adjusted between the water molecules. The shows that there are intermolecular gaps in water. 

(b) When an empty gas jar is inverted over a gas jar containing a colored gas, the gas also spreads into the empty jar. 

This shows that gases can fill up all the space that they get, and they have neither a fixed shape nor a fixed volume. They have no free surfaces, either. 

(c) A red ink drop added to small amount of water in a glass turns water red in some time. 

If we put a drop of red ink in a glass of water, its particles diffuse with particles of water slowly but continuously and the water turns red.

The smallest particle from which matter is made up is atom.

1. Matter—Anything that has mass and occupies space is called matter.

2. Intermolecular force — The force of attraction between the molecules of a given substance is called intermolecular force.

3. Element — It is defined as that pure substance which contains only one type of atoms e.g. hydrogen, chlorine.

4. Atom — An atom is the smallest part of an element that takes place in a chemical reaction.

5. Molecule — A molecule is the smallest part of a compound that exists independently.

1. Gases can be compressed easily: The reason for this property of gases is that there is very large intermolecular space between gas molecules. On mere applying pressure, they are easily compressed. 

2. Liquids can flow easily: In liquids, intermolecular force is weaker than that of solids. So molecules in a liquid can slip over one another and liquids can flow, unlike solids. 

3. We need to classify things: We need to classify things in order to distinguish them. In this way, things can be categorized and can be easily studied. 

4. Pure substances have fixed melting or boiling point : Pure substances consists of only one kind of matter. All the particles of a pure substance are alike. It has a definite composition and similar properties. This is the reason that pure substances have fixed melting or boiling points. 

5. Electricity is not considered matter: Electricity neither has mass nor it occupies space. Besides it cannot be seen by our eyes. This is why electricity is not considered matter.

Mass is the quantity of matter contained in the body.

Giving two examples of each type.

(a) Solid : A solid is that state of matter which has a fixed shape, mass and volume. It suffers very small changes in volume by changing the temperature. It cannot be compressed,

e.g. – Sand, Wood, Copper, Ice, etc.

(b) Liquid : It has a definite mass and volume but lacks a shape of its own. It takes up the shape of the containing vessels. It can be compressed to an extents,

e.g. – Milk, water, ink, etc.

(c) Gas : It is a state of matter which has only definite mass but no definite shape and volume. It takes up the shape of the container

e.g. – Carbon dioxide, oxygen, etc.

(a) Air is a matter because it has weight, mass and space and it can be compressed.

(b) The molecules are made up of atoms.

(c) The quantity of matter in an object is called its mass.

(d) The state of matter with a definite volume and definite shape is called solid.

(e) The substances which can flow are called fluids.

(a) The process by which matter changes from one state to another and back to original state, without any change in its chemical composition. 

(b)Intermolecular force of attraction. Intermolecular spaces are two important properties of matter that account for the different states of matter. 

(c) Matter can change from one state to another on changing temperature and pressure.

The particles are free to move in any direction i.e. they can flow because all substances that can flow are called fluids. Liquids and gases are fluids.

Characteristics of Matter

1. It can neither be created nor destroyed.

2. It is composed of a particular material which can either be Homogeneous or Heterogeneous.

3. Matter has, volume, mass and weight as per their state.

Water from oceans, rivers lakes from leaves of trees (transpiration) changes into vapors when the temperature increases or evaporates and enters the atmosphere as clouds when the temperature falls the vapors change into water and some of it in the form of snowfall on mountains and earth in the form of water and hales and this continues. Thus water cycle is an example of an inter convention of states of water.

When a solid is heated, its molecules gain energy and vibrate faster. A stage comes when they overcome the intermolecular force of attraction and start moving from each other. This results in melting of solid.

The advantages are: 

(i) Watershed management only increases the production and income of the watershed community. 

(ii) It also mitigates droughts and floods. 

(iii) It increases the life of the downstream dam and reservoirs.

General Properties Of A Solid :

1. Solids are hard that is, they have a definite shape and volume.

2. Solids are generally incompressible.

3. Solids are rigid, that is, they do not flow.

Molecules of a liquid are held by weak intermolecular forces. This force is strong enough to hold the molecules together but not strong enough to hold them at fixed positions. As a result liquids have a fixed volume but not shape.

The force of attraction between the molecules of a given substance is called intermolecular force and the space between these molecules is called intermolecular space. 

The basic relation between the two is that they are inversely proportional to each other. More is the intermolecular force lesser is the intermolecular space and vice-versa.

Wood charcoal is a better fuel than wood because of the following reasons:

• Its calorific value is higher than wood.

• It ignition temperature is lower than wood.

• It causes less air pollution.