A physical change is one in which the shape, size, appearance or state, of a substance may alter, but its chemical composition remains same.A change in which the composition of a substance is altered is called as chemical change.
Acids, bases and salts are three main categories of chemical compounds. These have certain definite properties which distinguish one class from the other.
The progress of the civilization was first benchmarked by man's increasing knowledge and usage of metallic deposits in the earth's crust. Early man used stones, bones and wood to fulfill their requirements of hunting, cooking and building.
Carbon compounds are of a second type which can be prepared from minerals such as oxygen, halogens and metals.
Initially scientists had classified elements into metal and non-metals. However, some elements possessed properties which could neither be classified as metals nor non-metals called metalloids.
Gaseous exchange involves movements of some specialised structures. The mechanism of taking in oxygen and giving out carbon dioxide is called breathing.
The study of transport mechanisms in plants helps us to understand the uptake of the various types of substances and their passage through the plants.
Steam pressure makes the wheels of the engine move. As coal is burnt, smoke is emitted and ash is left behind in the furnace.
As the complexity of the individuals, plants or animals increases the different cells and organs become separated from each other by greater distance.
Reproduction is thus essential for continuation of the species. It ensures that the genetic material of one generation is transmitted to the next. Each generation also produces more offspring for the next generation.
Heredity is the transmission of characteristics, physical or mental from parents to offspring that is, from one generation to the successive generation.
Light does not require a material medium for its propagation. In a given medium light travels with a very high but finite velocity.
The deviation in the path of light when it passes from one medium to another medium of different density is called refraction.
The eye lens converges these light rays to form a real, inverted and diminished image on the retina. The light sensitive cells of the retina gets activated with the incidence of light and generate electric signals.
A conductor having excess electrons is said to be at a negative or at a lower potential and that having less electrons is said to be at a positive or at a higher potential.
In a magnetic field, the magnetic dipole (Two equal and oppositely magnetised poles separated by a distance is referred to as magnetic dipole) experiences a turning force, which tends to align it parallel to the direction of the field.
The term 'energy' used here has thus a slightly different meaning. The term 'energy' actually means 'the useful energy' or 'the energy that we can use'; for cooking, operating machines, to run vehicles and so on. And we get this useful energy only from specific sources, which we call 'sources of energy'
The abiotic environment includes the air (atmosphere), water (hydrosphere) and land (lithosphere). The biotic environment includes the plants, animals and the microbes.
All our natural resources which we manipulate to satisfy human needs come from the environment. These are air, water, soil, minerals, coal, petroleum, animals and plants.