Ninth Science Chapter List & Description

Everything in this universe is made up of material which is called Matter.Things which have mass and occupy space are called matter. In other words matter has mass and volume both.

Early philosophers classified matter in the form of five basic elements, which they named "Panch Tatwa". These are air, earth, fire, sky and water.

In modern days matter is classified into two types on the basis of their Physical and Chemical properties.

Physical properties of Matter : Matter is made of small particles. Which can be seen by some simple activities, such as when salt or sugar is dissolved in water, salt or sugar is disappeared in water, i.e. spread throughout evenly. This happens as the particles of salt or sugar get into spaces between particles of water. . . .

Substances which are made up of two or more type of pure matters and can be separated by simple physical methods, are called MIXTURE. For Example: Air, salt solution in water, sugar solution in water, milk, etc. Air is the mixture of many gases, and thus called mixture.

Sugar solution in water, salt solution in water, cold drink, medicines, etc. are some other Examples of mixture.

Most of the Matters exist around us are not in pure form rather they exist in the form of Mixture.

On the composition of substances which form a mixture, Mixture can be divided into two types: Homogeneous Mixture and Heterogeneous Mixture.

Mixtures which have uniform composition throughout are called Homogeneous Mixture. For example: Salt solution in water, sugar solution in water. Homogeneous Mixtures are known as Solution also. In other words all the solutions are homogeneous mixture. . . .

When an object changes its place with time, the object is said to be in motion. And when an object does not change its position with time, the object is said to be in the rest.

To understand motion three things are needed to be considered, A Reference Point, Time, and An Object.

Example: Often we say that our school or a shop is 2 km or four km from our house. Here, our house is taken as a reference point, from where distance is considered.

Motion is of many types, such as motion along a straight line, motion along a circular path, zig-jag or erratic motion, controlled motion, uncontrolled motion, Uniform motion, Non-uniform motion, etc.

Motion Along A Straight Line: When an object changes its position with time along a straight line, this is called the Motion along a Straight line. . . .

Law of Constant Proportions states that In a chemical substance the elements are always present in definite proportions by mass.

Lavoisier, along with other scientists, noted that many compounds were composed of two or more elements and each such compound had the same elements in the same proportions, irrespective of where the compound came from or who prepared it.

Example: Water is composed of hydrogen and oxygen. A water molecule always consists of one part of oxygen and 2 part of hydrogen. And by mass a water molecule consists of mass of hydrogen to the mass of oxygen in the ratio of 1:8 whatever the source of water.

And, thus, when 9 g of water is decomposed, 1 g of hydrogen and 8 g of oxygen are always obtained.

Similarly, ammonia which is formed by the chemical combination of nitrogen and hydrogen, contains nitrogen and hydrogen in the ratio of 14:3 by mass. . . .

In general words; the force by which earth attracts all the objects towards it is called Gravitation. But, in scientific language; every object in the universe attracts every other object with an unseen force, and this force is called Gravitation or Force of Gravitation.

It was Great Issac Newton, English Scientist, who started thinking about the cause of falling of apple on him. He gave the theory about the Mystical Force of Gravitation, because of which everything fall on ground. Example: When we throw anything upwards, it falls down on the earth.

Motion of Moon round the Earth : Moon revolves round the earth because of force of gravitation exerted by earth on moon. Force of Gravitation of earth pulls moon towards it.

The motion of moon around the earth is due to the centripetal force. The centripetal force is provided by the force of attraction of the earth. If there were no such force, the moon would pursue a uniform straight line motion. . . .

Work is closely related to energy and power. We always use the term 'Work' in our day to day life. But there is a difference in the way we use the term 'Work' in day to day life and the way we use it in the science.

In day to day life if a person solved four to five chapters of math, then it is said that he is doing hard work, but in terms of science no work is done.

Suppose a person is pushing a big rock for a long hour and that rock does not move despite all the effort. In this process he may exhausted completely. Even though on work is done on the rock, because there is no displacement of the work.

Let again assume that a person stand still for couple of hours with a heavy load on his head. He gets tired completely in this process, but still in the language of science, work done is zero.

While reading a person does only metal work and not physical. Thus, work is something different in the context of science. . .

Sound is a form of energy. Sound produces sensation in our ears and we hear the sound. According to Law of Conservation of Energy, energy can only be converted from one form to another; it can neither be created nor destroyed. Thus, sound energy also is produced using other form of energy.

Examples : When we clap, a sound is produced. In clapping muscles energy is used.

Propagation of Sound : Reaching of sound from source to us is called Propagation of Sound. This means transmission of sound is called Propagation of Sound and not the travelling of sound. Sound does not transmit in vacuum. For transmission of sound, a medium is must. Without medium sound does not transmit from source to anywhere.

The matter or substance through which sound is transmitted is called Medium. Medium can be solid, liquid or gas. . . .

Cell is the fundamental structural and functional unit of life.

All living organisms are made up of cells. It is similar to a house; as a house is made of bricks all living organisms whether it is a plant or animals are made up by combining together many cells. The number of cells varies from organism to organism. According to estimates an adult human has about 100 trillion cells while an amoeba is a single celled organism. Human body has about 200 types of cells. Thus, it can be said that Cell is the basic structural unit of life. . . .