Differences between Evaporation and Boiling

Differences between Evaporation and Boiling

Evaporation	Boiling
Evaporation occurs at    all temperatures.	Boiling occurs at a fixed temperature.
Evaporation is a slow process.	Boiling is a fast process.
It is a silent process.	It is a noisy process.
It causes cooling.	It does not cause cooling.
It does not require an extra source of heat.	It requires and extra source of heat.
Evaporation takes place from the surface of the liquid.	The process of boiling takes place throughout the liquid.

Fig: Evaporation

Fig: Boiling

Open Circulatory System and Closed Circulatory System

• Open Circulatory System: In invertebrates like arthropod (insects, spiders) and certain molluscs, blood that is pumped by the heart into the arteries flows into a series of blood spaces within the body called sinuses.

• The body cavity in organisms having open circulatory system is called haemocoel and the blood is called haemolymph. Since the blood does not remain confined within the vessels, such a circulatory system is said to be 'open'.

Open Circulatory System in Grasshoppers

• Closed Circulatory System: In invertebrates like annelids, echinoderms and all vertebrates, blood flows through closed vessels, consisting of
•  Arteries
•  Capillaries 
•  Veins

Closed Circulatory System in Earthworms

John Dalton's Atomic Theory and other important scientists and their theories

John Dalton was an English school teacher who gave the first systematic idea of the structure of the atom. His statements are grouped together and are known as Dalton's atomic. He suggested that:

1. Atoms are small particles found in all matter. 
2. Atoms cannot be created nor be destroyed.
3. Atoms are indivisible.
4. Atoms of an element are identical.
5. Atom is the smallest unit of matter that takes part in a chemical reaction.

J.J. Thomson discovered the electron. Observations suggested that atoms contain negatively charged particles. He put forward the plum pudding theory of atoms. In this model of the atom, electrons are embedded in a sphere of positive charge.

In 1911, Ernest Rutherford suggested the following:

1. All atoms contain a small tiny central nucleus.
2. Most of the mass of an atom and all of the positive charge is being concentrated in the central nucleus. 

Neils Bohr suggested that:

1. Atoms revolve around the nucleus like planets around the Sun.
2. An electron can jump to a higher level by absorbing energy.
3. An electron fall to a lower level by giving out energy.

Rutherford-Bohr Model of an Atom

In 1932, James Chadwick discovered another subatomic particle i.e, neutrons which are present in the nucleus and have the same mass as the proton, but they have no charge.

Nuclear Fission and Fusion

Nuclear Fission: The process in which a heavy nucleus is broken into two roughly equal nuclei by bombarding the heavy nucleus with slow neutrons is called nuclear fission. The resultant nuclei are called "fission fragments".

During nuclear reaction, the total mass of the products is always less than the mass of the original nucleus. The difference in mass is converted into energy in accordance with Einstein's mass-energy equivalence equation E=(mc)(mc) where m is mass, e is energy and c is the velocity of light.




Nuclear Fusion: The combination of two or more light nuclei to form a heavy nucleus with the liberation of a large amount of energy is called nuclear fusion. The energy liberated in the fusion reaction is called thermonuclear energy.

Transpiration and Translocation

Transpiration is the process by which plants give out excess water in the form of water vapour. It can be of three types:

1)Stomatal Transpiration

2)Lenticular Transpiration

3)Cuticular Transpiration

'The water is lost from the aerial parts of the plant.
'It takes place in day and night.



Translocation is the process by which minerals absorbed by the roots and carbohydrates prepared by the leaves are dissolved in water and transported in the form of solution.

'Phloem transports the nutrients during Translocation.

Intermolecular Forces and Kinetic Theory

All matter is composed of atoms or molecules which are tightly packed or held together in liquids and solids. The forces that hold these atoms or molecules together are called inter-molecular forces. Inter-molecular forces are the greatest in solids, lesser in liquids and least in gases.

Kinetic theory is also termed as ‘thermal motion’. It is related to movement or motion of particles when a substance in any one of the three states of matter is heated.

In solids, as there are strong inter-molecular forces of attraction, the atoms or molecules are fixed. Hence, they vibrate about their mean position.

In liquids, the molecules can move about but they remain in contact with each other.

In gases, molecules move about freely and travel in straight lines until they collide with objects or one another.