Basic science jss2

Ecological relationship involves interaction between living organisms in their habitat.

For work to be done , a force must be applied and this force must produce a displacement in any direction except perpendicular to the direction of the force . For  eg. A man pushing a wheel barrow exerts force in the same direction as the distance of the wheel.

Mechanical energy is the energy used in moving something ( a body ) from one place to another.Mechanical energy is composed of potential energy and kinetic energy. Potential energy means energy by virtue of position. A coconut fruit on a coconut tree has a great potential energy by virtue of its location high above the ground.kinetic energy is the energy by virtue of the movement of a body.If the coconut fruit falls from its tree,its potential energy is converted to kinetic energy.

    CALCULATIONS   INVOLVING  WORK DONE

The work (W) done by a force (F) is the product of force and  distance (d) in the same direction of the force, ie. W=Fd.

The Kinetic theory  of matter assumes that matter is made up of tiny particles such as atoms,molecules and ions that are continually moving and therefore possess kinectic energy.

A British Scientist,Dalton,about  1806AD,expanded the idea of atoms.He made various statement about the nature of atoms.His ideas about atoms are stated below:

1.Matter is made up of minute indivisible particles called atoms.

2.Atoms cannot be created or destroyed.

3.All the atoms of an element are alike and different from the atoms of all other elements.

As  heat energy is applied to the liquid state of matter ,the temperature and therefore the speed of the molecules increase.Continous application of heat raises the temperature to boiling point.Evaporation which occurs at any temperature is the escape of molecules of a liquid from its surface.

A  chemical substance is a form of matter that has a constant composition and characteristic properties. It cannot be separated into components by physical separation methods. A common example of a chemical substance is pure water.It has the same ratio of hydrogen to oxygen.

Some non -living things are elements , some are compounds while some are mixtures. An example of an element is gold .water and common salt are compounds while air is a mixture.

    As animals, human beings must move about in search of food , shelter and other basic needs of life. Movement in human beings is possible by the possession of special structures such as bone , joints and muscles.

The process by which food substances are broken down into simpler and soluble form is called digestion.All the parts of the body which work together to ensure digestion of food make up the digestive system.