Organizational patterns of living organisms

Red beetles-  Photo by : Vidura Nishantha

Cell is regarded as the basic structural and functional unit of life. The tissues are made up of similar cells. Differentiated  smaller units arranged in an orderly manner  to form larger units is called organization. There are different levels of organizations.

 lower levels include:

molecules ----> organelles  ---->cells  ---->tissues  ----> organs  ----> organ systems  ----> organism

higher levels include:

organisms  ---->population  ----> community  ---->ecosystem  ---->biosphere

Definitions:

• Population: all individuals of a species in a particular area

• Community : Population of different species present in a particular area

• Ecosystem: Living beings interacting with non living components

• Biosphere: Different ecosystems of all geographical regions of the world

The Chemistry And Uses Of Acids, Bases And Salts

Acids , bases and salts are types of chemical substances with special properties.

Acids:

Acid is defined as- a substance that produces Hydrogen ions to the aqueous solution.
There are more definitions purposed for the definition of acids also.

Acids are sour tasted, turns blue litmus paper red having a pH value less than 7

Hydrochloric acid secreted in the stomach, vinegar are some examples for commonly known acids.

Acids are also divided in to two types, Strong acids, weak acids.

Strong Acids: Strong acids completely ionizes to produce Hydrogen ions to the solution.

e.g: HCl (aq) -> H+(aq)  + Cl-(aq)

Weak Acids:  Weak acids dissociate partially in the aqueous solution to produce less concentration of hydrogen ions to the solution.

e.g: ethanoic acid

Bases:

Bases are defined as : a substance that reacts with acids to produce salt and water only. 

Bases has a soapy texture, turns red litmus blue and has a pH value higher than 7

Bases can be soluble or non soluble. 

Soluble bases such as sodium hydroxide is known as alkali

Bases also divides in to strong bases/alkali or weak bases/ alkali

Strong alkali: ionizes completely into hydroxide ions in the aqueous solution

e.g  NaOH (aq) -> Na+ (aq) +OH-(aq)

Salts: 

Salts are the product of reacting acids with base. 

Salts are neutral , does not change the color of limus paper and has a pH of 7

E.g NaCl

Next about preparation of salts

Structure and properties of materials

Properties of all substances we come across in chemistry is based on their structure.

Before going into details  try to define the following

1. What is an atom?

2. What is meant by element?

3. What is the difference between a compound and a mixture?

Answers:

1. Atom is the smallest particle that makes up matter

2. A substance that is made with only one type of atom

3. Compound is the product of combination of two or more types of atoms and mixture is a substance made with two or more chemically unchanged substances

Two allotropes of carbon can be found as graphite and diamond. Even if these are made with the same type of element their properties are different.

Diamond is hard graphite is soft

Diamond cannot conduct electricity but graphite can

These differences are due to their giant structure.

Diamond has four carbon atoms bonded to each carbon atom covalently making a hard giant atomic lattice.

In graphite each carbon atom if bonded with three more carbon atoms covalently making a layered structure. delocalized electron from each carbon atom floats between these layers making layer to slide over each other when a force is applied (lubricant property) and these free moving electrons can conduct electricity , making graphite a good electrical conductor.

Next Topic: Ionic bonding