Tuesday, 11 September 2018

Chemistry: Molar Mass, Examples and Solutions



Molar mass

The formula mass or molar mass of a compound is the mass of the correctly written formula or one molecule of the compound, obtained by adding together the appropriate relative atomic masses of the atoms of the elements present in the molecule.

Sunday, 2 September 2018

Sunday, 29 July 2018

Liquid expansion: Real and apparent expansion, cubic expansivity.




Expansion of liquid; Real and apparent expansivity

Like solid, liquid expands on heating and contracts on cooling, because liquid is always held in a container, the expansion of liquid is always complicated because of the expansion of the container itself.

Monday, 23 July 2018

Physics: Anomalous Expansion of Water


Anomalous expansion of water

Anomalous expansion of water

This means something that is unusual. The temperature range of water from 0°C to 4°C is unlike most substance because is volume decreases as the temperature increases. 

Monday, 16 July 2018

Periodic table: periodic law, groups, periods

Periodic Table
Table of Contents
1) What is periodic table?
2) What is the periodic law?
3) What are Groups?
4) What are periods?
5) Families of Elements
6) Group 0 to 7 properties.









Periodic table
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number and electron configuration. The periodic table is divided into eight (8) vertical columns known as "Groups" and eight (8) horizontal columns known as "Periods".

Monday, 27 November 2017

Atomic Structure: Definition, History and theories

     Introduction of Atom

Introduction to atom


Define of Atom:-

  The Greek philosopher Democitus (460B.C – 370 B.C) was among the first to suggest the existence of Atoms (from the Greek word “atoms” means indivisible).

He believed that atoms were indivisible and indestructible. His ideas dis agree with later scientific theory, but did not explain chemical behaviour, and was not based on the scientific method, but just philosophy.


Dalton’s Method:-

 John Dalton took what was known about chemical reactions at his time and proposed the first atomic model.


Conservation of Mass

  • Law of Multiple Proportions
  • Law of Definite Composition



Billiard Ball Model:- 

Dalton combined the observation into one theory which stated that all matter was composed of small indivisible particles that he called atoms.

Demitri Mendeleev used this theory when he constructed the first working periodic table.


Dalton’s Atomic Theory (experiment based):-


  1. All elements are composed of tiny indivisible particle called atoms
  2. Atoms of the same element are identical. 
  3. Atoms of any one element are different from those of any other element.
  4. Atoms of different elements combine in simple whole-number  rations to form chemical compounds. E.g CO2

In chemical reactions, atoms are combined, separated, or rearranged, but never changed into atoms of another element.


Sizing up to the Atom:-

 Elements able to be subdivided into smaller and smaller particles, those are the atoms, and they still have properties of that element
If you could line up 100,000,000 copper atoms in a single file, they would be approximately 1cm long.

Despite their small size, individual atoms are observable with instruments such as scanning tunnelling microscopes.



Cathode Ray:-

 Crookes worked in the areas of chemistry and physics. He had many accomplishments, one of which was the discovery of cathode rays.


Crookes Tube:-

A source of high potential difference was placed across the cathode of a glass tube that had gas at a very low pressure inside.
Noticed a glow coming from the negative terminal.


Properties of Cathode Ray:-

A wide variety of cathodes (different metals) were tested and all produced same results.

Magnetic fields deflected the rays.
The rays produced some chemical reactions similar to those produced by light.

The rays travelled in straight lines, perpendicular to the surface of the cathode.


History:-

Electron means “amber” in Greek
Properties discovered by the Greek Thales of Miletos 600 BC. Rubbed the mineral amber with cat fur and attracted feathers.

J. J. Thomson discovered the electron while experimenting with cathode rays. In 1897, J. J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle: The Electron.


Cathode Ray:-  
Thompson showed that the production of the cathode ray was not depend on the type of gas in the tube, or the type of metal used for the electrodes. He conludes that these particles were part of every atom.


Cathode ray

Thomson’s Charge to Mass Ratio:- It was noticed that the beam of electrons be bent by a magnetic field. This means that: Fnet = Fm
So,
mv2 = Bqvr
so, q/m = v/Br.

Saturday, 25 November 2017

Biology: Mitosis vs Meiosis, definition and differences.



Mitosis and meiosis



Mitosis

This is the process by which cells increases in number and achieves growth. Mitosis occurs in five stages namely; Interphase, prophase, metaphase, anaphase and telophase. 

Mitosis occurs in somatic or body cell such as skin, bone marrow, lymph nodes and injured places as well as meristematic tissues in plant.

i) Interphase: In this phase,
  • chromosone becomes elongated and forms a network of fine thread called chromatid.
  • The nuclear membrane is nearly visible.
  • The nucleolus is also visible.



ii) Early prophase: In this phase,
  • Chromosone becomes visible as the chromatid thread condenses.
  • Chromosone are lone and thin.
  • The nucleolus starts to shrink.
  • There is a formation of spindle fibres.



    Late Prophase: In this phase,
  • chromosone becomes faster, thinner and very visible.
  • The nuclear membrane disappears.
  • The nucleolus disappears entirely.



iii) Metaphase: In this phase,
  • The chromosome arranges themselves along the equator.
  • The chromatids are attached to the spindle be the centromeres.



1v) Anaphase: In this phase,
  • The chromatids separate.
  • The chromatids start migrating to the poles.
  • The chromatids eventually get to the poles.



v) Telophase: In this phase,

  • The cell starts dividing into two.
  • The chromosone now loses their thick appearance.
  • The spindle structure disappears.
  • The daughter cells are formed.

Mitosis






Importance of mitosis

  1. It ensures that the diploid condition of the cell is retained from generation to generation.
  2. It helps in growth of multi-cellular organisms.
  3. It helps in asexual reproduction of animal and plant.
  4. Mitosis ensures that the exact copy of DNA (deoxyribose nucleic acid) are transmitted to daughter cell.




Meiosis

It is a two-successive cell division with my one duplication of chromosones. Meiosis is a reduction in cell division and the resulting in daughter cells. 

For example,
  • Ovules and pollen grains in plants.
  • Ovaries and testes in animals.


In animals, meiosis occurs in the formation of gametes sex cells such as eggs and spermatozoa. The process of gametes formation is called gametogenesis. The process involved in the production of spermatozoa by testes is called spermatogenesis, while the process of producing eggs by the ovaries is known as Oogenesis.


Importance of Meiosis

  • It aids formation of sperm in animals.
  • It aids formation of eggs or ova in female animals.
  • It aids the formation of pollen grains in flowering plants.
  • It aids the formation of ovules in flowering plants.






Differences between Mitosis and Meiosis

Mitosis
Meiosis
a) It occurs during the growth
of somatic cells and asexual
reproduction.
It occurs during
gamete’s production.                 
b) Two daughter cells or
off springs are formed
Four daughter cells or
off springs are formed.       
c) Chromosone number of
daughters and parent’s cells
are equal.                                         cells Is half the number
The chromosone
number of daughter cells
is half the number
in the parents’.

d) Off-springs produced by
mitosis is the exact replicate of the parents
Off-springs produced
by meiosis will show
Variation.
                                                                         











Sunday, 19 November 2017

Chemistry: What is Hydrogen? It's Uses, physical properties, chemical properties and methods of preparation



Hydrogen


Hydrogen is found in group one of the periodic table. Though, it is non-metal, it is usually placed in group one because it has one valence electron.

PERIODIC TABLE HYDROGEN



Physical Properties of Hydrogen
  •  It is a colourless, odourless and tasteless gas.
  • It is neutral to litmus paper.
  • It is insoluble in water.
  • It is the lightest substance known.
  • It has a very low boiling point of (-253-degree Celsius).
  • It is less dense than air.


Chemical Properties of Hydrogen


     1. It reacts with metals to found hydrides.

              
             2Na + H2 ---> 2NaH

     2. It burns in air to produce steam.
    
             H2O + O2 ---> 2H2O

    3. It reacts with halogens to produce halides

            H2 + Cl ---> 2Hcl
            H2 + 2Br ---> 2HBr

   4. Acts as a Reducing agent: It reduces oxides to their respective metals
  
           CuO + H2 ---> Cu + H2O


Uses of hydrogen
  • It is used in the hydrogenation of oil.
  • It is used to manufacture soap and margarine (saponification).
  • It is used in filling balloons.
  • Liquid hydrogen is used for rocket fuel.
  • It is used for welding metals.


Isotopes of hydrogen

Hydrogen has three naturally occurring Isotopes. There are;
  • Protium – ( 11H )
  • Deuterium – ( 12H )
  • Tritium - ( 13H )
“Deuterium oxide” is commonly known as heavy water because it is about 1.1 times heavier than water.  “Protium” has no neutrons, it is the ordinary isotope of hydrogen. “Tritium” is radioactive and rarely found in ordinary hydrogen.

TRITIUM


Read more about: Isotopes and isotopy (chemistry)


Laboratory Preparation of hydrogen

Hydrogen can be prepared in the laboratory by;

* Action of dilute acid on metal.
* Action of cold water on sodium.
* Action of steam on red hot iron


Laboratory preparation of hydrogen by the action of dilute acid on metal.

AIM – To prepare hydrogen.                                                                      

APPARATUS – Round bottom flasks, delivery tube, glass jar, thistle funnel, trough etc.

METHOD
  • Place some pieces of zinc metal in a round bottom flasks
  • Set up the apparatus.
HYDROGEN LABORATORY SET UP

  • Add dilute sulfuric acid (H2SO4) to zinc metal through the thistle funnel.
  • Collect the gas formed over water.

OBSERVATION – As soon as the metal effervescence occurs, gas liberated is collected over water.

CONCLUSION – Hydrogen can be prepared in the laboratory




Industrial preparation of hydrogen

Hydrogen can be prepared in large quantities in the industries by the following ways;
  • Water Gas
  • Hydrocarbon
  • Electrolysis


By Water Gas

When steam is passed over red hot coke at a temperature of about 1100 degree Celsius. The mixture of carbon (ii) oxide or hydrogen gas is produced and this is known as water gas.

H2O + C ---> CO + H2

The product obtained is mixed with excess steam and passed over iron(iii)oxide or Uranium (iii) oxide as a catalyst at a temperature of 450 degree Celsius.

During this process, carbon (ii) oxide in water gas is converted to carbon (iv) oxide and the liberation of excess hydrogen.

CO + H2 + H2O ---> CO + H2

Questions? Comment below.
        


Sunday, 30 July 2017

Physics: static electricity, electric charges and law of charges.

What is electricity?

     The is a form of energy that occurs when electrons flows through a conductor.


Areas Covered

  • Definition of static electricity
  • Nature of atoms of static electricity
  • Electricity charges
  • Law of charges
  • Conductor and insulator

Definition of static electricity


     Static electricity is  produced by the friction between two materials. For example, when rod is rubbed with silk.

Sunday, 26 March 2017

Physics: Introduction to radioactivity,types and properties.

radioactivity

Radioactivity

It is a spontaneous emission of radiation from a substance usually an unstable   .This process is also known as nuclear or radioactive decay). In the year 1896, Henri Becquerel a French scientist working with phosphorescent materials discovered that a uranium compound placed on a photographic plate which was covered with light black paper causing the plate to be exposed by blackening the pate itself. This implied that some sort of radiation was coming from the uranium which could pass through. The material was radioactive given-off radiation. Other scientists that researched on radioactivity were;v This radioactivity was spontaneous with the radiation being omitted without anything causing it apparently.

Types of radioactivity

From several experiments that have been carried out, it has shown that there are three different types of radioactive emission called;
 Alpha particles ; whose emission is easily stopped by paper or thick card
 Beta particles ; whose emission is easily stopped by aluminium sheet of different thickness and are negatively charged.
Gamma particles ; whose emission is easily stopped by thick sheet of lead.

types of radioactivity


Properties of alpha particles


      1)  Alpha rays are deflected by magnetic field.  
      2)      The direction of deflection of alpha rays shows that they are positively charged
      3)      They are relatively massive and so have more momentum and tend to continue in their direction of travel.
      4)      Alpha particles are absorbed by paper and air and are easily stopped aluminium thin sheet.
      5)      They have little penetrating power, travelling no more than 5cm. Being large, it is soon stopped by air molecules.
      6)      They are capable of stripping electrons from their atoms because alpha particles have comparatively large mass and momentum.


Properties of beta particles

     1)      There are also deflected by magnetic field but in the opposite direction to alpha particles.
     2)      The direction of deflection of beta rays shows that they are negatively charged with –e .
     3)      They are relatively light and as a result easily deflected.
     4)      They are deflected by different amount showing that they have varying speed..
     5)      They have good penetrating power of about 1 metre.
     6)      They can penetrate a few millimetre of aluminium.
     7)      They produce less ionisation in air than alpha particles.

Properties of gamma rays

    1)      They are electromagnetic waves similar to light wave but of very short wavelength.
    2)      They are electrically uncharged since they are not deflected by a magnetic field.
    3)      They are highly penetrative compared to the other two types and can only be stopped by thick lead blocks.
   4)      They have high penetrating power compared to the other two types.
   5)      They have much less ionisation than alpha rays.

Sunday, 12 March 2017

Physics: Thermal, linear, area and cubic expansivity

Thermal expansivity


Expansivity

 This is defined as amount a material expands or contracts per unit length, per-degree change in temperature.
The addition of heat will usually cause expansion of the body. during expansion, the dimension of the body increases.

Wednesday, 8 March 2017

Introduction to Energy, conservational law, Mechanical energy; potential and kinetic energy, examples






Energy




Energy can be defined as the capacity to perform work. Thus, the unit of energy is the same as that of work. That is, the s.i unit of energy is joule. We have various types of energy; kinetic energy (Such as, the energy from a moving car or a falling stone), chemical energy, heat energy, electrical energy,  light energy, light energy, sound energy, nuclear energy.

Conservation law

 All the forms of energy listed above can be changed from on form to another by means of suitable machine or apparatus, for example; the energy in the nucleus of atoms produces heat energy, which in turn can be used to generate electrical energy. The mechanical energy that moves a car comes from heat  energy derived from the volume of fuel which is stored as chemical energy.


The principle of conservation of energy states that although energy can be changed from form to another, the total energy of given system remains unchanged i.e energy can neither be created nor destroyed during transformation.

Mechanical Energy

A body can possess mechanical energy or have the ability to work for two reasons either by virtue of its position or because of its motion. The two kinds of energy are called kinetic energy and potential energy respectively.

Kinetic energy

  It is energy a body possesses because it is in motion.
Mathematical formula, 
   KE =   1/2 mv2       Where m = mass, v = velocity.

Other forms of kinetic Energy:


  1. Electrical Energy: This is the movement of electrons. Examples: lightning and electricity. 
  2. Motion: This is the movement of substances from one place to another. 
  3. Thermal Energy: This is the movement and vibration of atoms and molecules within a substance. For example, geothermal energy. 
  4. Radiant Energy: This is electromagnetic energy that travels in transverse waves. Examples: X-rays, gamma rays, Alpha rays and so on. 
  5. Sounds: This is the movement of energy through substances in longitudinal waves. 




Potential energy

   It is the energy a body possesses because of its position. A body of mass (m) raising to a height (h) above the ground is said to possess potential energy.
   Mathematical formula, 
   KE = mgh       Where m = mass, g = acceleration due to gravity, h = distance.

Other forms of kinetic Energy:


  1. Chemical Energy: This is the energy stored in bonds of atoms and molecules. Examples: petroleum, natural gas, coal and so on. 
  2. Gravitational Energy: This is the energy of place and position. 
  3. Nuclear Energy: This is the energy stored in the nucleus of an atom. For example, the nucleus of uranium atom.

 

Power: This is defined as the rate of doing work or the rate of transfer of energy.
Average power = (work done or energy extended)/(time taken)
Power = (mgh)/t
     The S.I unit of power is watt (W),former unit of power was horse-power.


Examples

  1) A boy of mass 30kg is running with a speed of 4 m/s. What is his kinetic energy?
Solution
KE =   1/2mv2
M = 30kg, v = 4m/s
KE = 240J

 2) A bullet of mass 4g is moving with a speed of 216 km/hr. Calculate its kinetic energy.

Solution

M = 0.04 kg
V = 216km/hr
1hr = 60min
1000m = 1km
V =  60m/s
KE =72J

3)  Calculate the power of a pump which lifts 500kg of water through a vertical height of 4m in 5 seconds.

Solution

P = mgh/t
m = 500kg
h=4m
g=10m/S2
Power = 4000J

 4) A bullet of mass 0.05kg has a speed of 400m/s. What is the kinetic energy, if it hits a wall of which of the average resistance is 10000N. Calculate the distance penetrated by the bullet.

Solution

   KE =   1/2mv2      
KE = 0.5 x 0.05 x 400 x 400
KE = 4000J
Energy =work done = Force x distance
4000J = 10000 x d
Distance penetrated by the bullet = 0.4m