Clayey Soil: Particles of clayey soil are very small in size. This makes the particles of clayey soil packed tightly. There is very little space among the particles. Water does not drain quickly through clayey soil because of less space among particles. So, clayey soil is not well aerated and retains more water. Clayey soil is used in making of toys. Clayey soil is good for growing paddy.

Alkali: The hydroxides of IA & IIA group elements are called Alkalies. They readily soluble in water. Alkalis are the bases that are soluble in water. All alkalis are bases but all bases are not alkalis.
Base:  The hydroxides formed by the elements other than IA & IIA group elements are called Bases. They are not easily soluble in water. Bases are the substances that are soapy to touch and are bitter in taste. They give blue colour with litmus paper .

• First law of reflection states that the incident ray, the normal to the surface at the point of incidence and the reflected ray, all lie in the same plane.

Take a torch and cover its glass with a chart paper which has three slits. Spread a sheet of chart paper on a smooth wooden board. Fix a plane mirror strip vertically on the chart paper. Now direct the beam of light on the mirror from the torch with slits. Place the torch in such a way that its light is seen along the chart paper on the board. Now adjust its position so that the light from the torch strikes the plane mirror at an angle. The plane mirror reflects the three rays of light falling on it.

Similarly, place a lighted candle in front of a plane mirror. Try to see the flame of the candle in the mirror. It appears as if a similar candle is placed behind the mirror. The candle, which appears behind the mirror, is the image of the candle formed by the mirror. The candle itself is the object and now moves the candle to different positions in front of the mirror. The flame appears on top of the candle as in the object is called erect. An image formed by a plane mirror is erect and of the same size as the object.

Change in which only physical properties of a substance change and no new substance is formed is called Physical Change. Most of the physical changes are reversible, this means we can get the substance back even after the change.
Example:Folding of a paper sheet:

Rusting of iron occurs only if iron comes in contact with moist air. In coastal areas, air contains high percentage of moisture because of sea or ocean, while in deserts air is dry and hot. As the percentage of moisture in air is more in coastal area compared to desert, rusting becomes faster.

A Cyclone is a large scale air mass that rotates around strong centers of low pressure.
The structure of cyclone contains:

• Eye – Low pressure and area of sinking air. Its diameter ranges from 10-100 kms.
• Eye Wall – Dense cloud surrounding eye having maximum wind speed. It causes maximum destruction.

Spiral rain bands – Band of clouds spiraling into eye wall and it contains heavy rains

Climate has an intense effect on all living organisms. Animals adapt themselves to survive various conditions in which they live. Animals that live in extreme climates acquire some special features to protect themselves from it. Animals evolve to acquire these features and habits to adapt to their environment.
 

Inertia may be defined as the internal force of a free standing body that resists acceleration caused by the application of an external force upon that body.

Whether in motion or not is not relevant, inertia is the resistance of a body to an applied force causing acceleration of that body, particle or whatever, providing it contains a charge(s). It can be determined by dividing the applied force by the acceleration caused by that force. Inertia = F/a. Both F and a are measurable.

In case of the spinal cord injury, the signals coming from the nerves as well as the signals coming to the receptors will be disrupted. As both these signals meet in a bundle in spinal cord so there is any spinal cord injury then both these signals are disrupted.  

Air exerts pressure in all directions.  The pressure exerted by air is called the air pressure, which is the thrust exerted by air per unit area. 

Factors Affecting Air Pressure:

1. Temperature:  As the temperature increases, air expands because of which its density decreases which results in low pressure. On the other hand air shrinks due to low temperature because of which its density increases which creates high pressure.

2. Height from Sea Level: Air pressure is created due to weight of air therefore sea level has highest air pressure. As we move upward from sea level leaving behind the heavy gases at lower layers of atmosphere, air pressure decreases because the upper air is light and its density is low.

3. Moisture in Air (Humidity): Conversion of water from liquid state to gaseous state because of evaporation is known as atmospheric humidity. Water vapours are light in weight therefore they rise up and pressure of humid air decreases as compared to dry air. Amount of water vapours changes with time and place and because of this the pressure of air also varies.

The transfer of heat because of movement of the molecules of the medium; via mass transfer; is called convection or convection of heat.
In coastal areas, the breeze that moves from sea surface to the land is called sea breeze. This happens because, during daytime, land gets heated more quickly than water. As a result, warm air from land rises up; leaving a gap. To fill that gap, colder air from the ocean surface rushes towards the land. This phenomenon continues and a continuous flow of cold air keeps coming towards the land. This gives rise to the phenomenon which is called the sea breeze.
In coastal areas, the breeze which moves from land towards the sea is called land breeze. In the night, the land cools down more quickly than the ocean surface. This makes the air over the water surface warmer than air over the land surface. Warmer air over the water surface rises in the air and air from the land rushes towards the water surface to fill the gap. This phenomenon continues which creates a flow of air from land to the sea. This phenomenon is called land breeze.

Sandy Soil: Particles of sandy soil are larger in size. Because of being larger in size, sand particles cannot fit close together and hence there is enough space among them. These spaces are filled with air. Water drains quickly through sandy soil. So, sandy soil is called well aerated, light and dry. Sandy soil is not fit for vegetation as it does not retain water. However, millets can be grown on sandy soil.

Clayey Soil: Particles of clayey soil are very small in size. This makes the particles of clayey soil packed tightly. There is very little space among the particles. Water does not drain quickly through clayey soil because of less space among particles. So, clayey soil is not well aerated and retains more water. Clayey soil is used in making of toys. Clayey soil is good for growing paddy.

Loamy Soil: Particles of loamy soil are smaller than sand and larger than clay. Loamy soil is the mixture of sandy soil, clayey soil and silt. Silt is the deposit in river beds. Loamy soil has right water holding capacity and is well aerated. This is considered as the best soil for the growth of plants.

In unicellular organisms, transportation of substances happens through diffusion and osmosis. Gases move in and out of the cell by diffusion. Other substances move by osmosis.

Diffusion: Random motion of particles in order to attain equilibrium of concentration is called diffusion. Diffusion can be observed in many aspects of day to day life. The aroma of food comes from the kitchen because of diffusion. A pleasant smell of flowers comes because of diffusion. Bad odour of garbage comes because of diffusion.

Osmosis: Movement of water through a semi-permeable membrane from high water concentration to low water concentration is called osmosis. Osmosis is a type of diffusion. Cell membrane is a semi-permeable membrane. Substances move across the cell membrane because of osmosis. Seeds swell up; when soaked in water; because of osmosis.

The plants which belong to Leguminosae family and produce fruits as pods are called leguminous plants.These plants have bacteria in their root nodules which fixes atmospheric nitrogen into soil.Examples of leguminous plants: Peas, beans , soy etc.