Plasmolysis through the effect of Isotonic for std 10 to 12

Practical-2
AIM :-
Study of Plasmolysis through the effect of Isotonic, Hypotonic as well as Hypertonic Solutions
of Sodium Chloride and  Potassium Chloride on Mounted Epidermal Cells of Tradescantia leaf.
INSTRUMENTS AND MATERIALS : -
Slide, Cover slip, Microscope, Dropper, Blotting paper, Tradescantia leaf, Water, Glycerine, NaCL solution, KCL solution.

Plasmolysis through the effect of Isotonic for std 10 to 12

Conclusion :-
This a kind of exosmosis. When living plant cell is placed  in a concentrated solution of sugar or salt plasmolysis is induced in them. Normally living cells are turgid as concentrated of vacuolar sap is lower than the surrounding solution water from the cell starts moving outside through exosmosis.

Oxygen is evolved during photosynthesis. Std 10 to 12

AIM :  To show that oxygen is evolved during photosynthesis.

PRINCIPLE :  During photosynthesis photolysis of water takes place  and oxygen is released.

Equation for oxygen evolved during photosynthesis.

MATERIALS       :  Beaker, funnel, test tube, twig of Hydrilla, water.

  

Oxygen evolved during Photosynthesis

Bubble comes out 

Oxygen evolved during photosynthesis

Result :

Air bubbles released from the cut end of plant twigs move up through the funnel and get collected in the test tube.

Conclusion :

The oxygen produced during photosynthesis moves up in thee form of bubbles and getts collected in the test tube.

Application : 

During photosynthesis oxygen evolved and released in the atmosphere. It can be shown to the students by the above experiment.           

Stomata in Lower Epidermis of leaf, Biology std 10 to 12

To study the stomata present in the epidermis of leaf by preparing a temporary slide.

AIM :   To study the stomata present in the epidermis of leaf by preparing a temporary slide.

PRINCIPLE :  As the lower epidermis is not directly exposed to sunlight it contains more number of stomata. This reduces the rate of transpiration.

MATERIALS :  Leaf of Hibiscus, Nagervel (betel leaves) or Maize, slides, forceps, scalpel or blade, Microscope

Lower and Upper Epidermis of Nagarvel leaf.

Scratch of Nagarvel leaf on Lower epidermis

Stomata view in Microscope.

Stomata viewed in Microscope

Enlarge view of  stomata.

Result

Maximum number of stomata are visible as the lower epidermis has more number of stomata. In Hibiscus and Nagarvel the guard cells of stomata are been shaped while in Maize they are dumb-bell shaped.

Conclusion :

By this method stomata can be seen and counted under the microscope.

Application :

This is an easy method to show the stomata to the students.

ISOTOPES AND RADIO-ISOTOPES Science for 8 to 12

Isotopes : 
 Atoms of a given element, have the same atomic number, that is they contain the same number of protons. However, they may contain different numbers of neutrons. They correspond to the same element and are chemically indistinguishable; they have different mass numbers 
(Iso means same, tope means same place; they occupy the same place in the periodic table).

Therefore atoms of the same element having same number of protons 
(atomic number but different number of neutrons (different mass numbers), are called isotopes. Isotopes may be naturally occurring or artificially made.

Example : Normal hydrogen (protium) 1H1 deuterium 1H2 and tritium 1H3 are the isotopes of hydrogen. 6C11, 6C12 and 6C14 are the isotopes of carbon. Uranium has two isotopes namely 92U235 and 92U238.

Radio-istopes : The term radio-isotope is the shortened from of radioactive isotope. If the isotope of an element is radioactive, then the isotope is called. radio-isotope, referred to as radio-nuclide. At least one radio-isotope of every element is available. Over a thousand of them can be made artificially, mostly in nuclear reactors using slow neutrons as bombarding particles.

Examples : Cobalt-60 an isotope of cobalt is radioactive; It is usually refereed to as radio-cobalt. Radio-iodine (I131), radio-iron (Fe59) radio-sodium (Na24), radio-phosphorous (P30), radio-cobalt (Co60), radio-sulphur (S35) and radio-carbon (C14) are some of the radio-isotopes.

Uses of Radio – Isotopes : Radio-isotopes find applications is various fields, some are listed below.

Radio-phosphorous is used in agriculture to determine the kind of phosphate required for a given soil and crop.

Radio-iodine is used in the treatment of overactive thyroid glands and radio-cobalt in the treatment of cancer, Radio-sodium is used to study the action of medicines.

Radio-cobalt or radio-iridium is used in industry to check machine parts.

Radio-carbon is used to estimate the age of fossils and archaeological specimens.

POINTS TO REMEMBER

 Spontaneous disintegration of certain unstable atomic nuclei with the emission of certain radiations is called radioactivity.

 Becquerel rays are the radiations emitted by radioactive elements.

 The elements from atomic number 81 to 92 are found to be radioactive.

 The radioactive radiations are alpha (alpha) particles, beta (beta) rays and gamma (Gama) radiations.

  (alpha) - particles are nothing but helium nuclei, 
- rays are stream of electrons and 
- radiations are high energy photons.


 The changing of one element into another is known as transmutation. Original atom is parent atom and the new atom produced is the daughter atom.

 Half life of a radioactive element is the time taken by a radioactive sample of that element, to get reduced to half its mass.

 Half life varies from microseconds to billions of years.

 The phenomenon by which radioactivity is induced in an element, is called Induced radioactivity or artificial 

radioactivity.

 When a stable aluminum atom is bombarded by (alpha) particles it becomes radio phosphorus.

Atoms of the same element having same number of protons (atomic number) but different number of neutrons (different mass number) are called isotopes.

Isotopes of Hydrogen are Normal Hydrogen (protium) (1H1), Deuterium (1H2) and Tritium (1H3)

Isotopes of Carbon are 6C11, 6C13, and 6C16,

Isotopes of Uranium are 92U235 and 92U238

It the isotope of an element is radioactive, then the isotope is called radio isotope, referred to as radio nuclide. Radio nuclides are manufactured in nuclear reactors.

INDUCED RADIOACTIVITY science for 8 to 12

The phenomenon by which radioactivity is induced in an element, is called induced radioactivity or artificial radioactivity.

When a stable nucleus is bombarded with a high energy particle, it gets changed into another which is often radioactive. For example, when aluminum is bombarded by a (alpha) particles, it produces radio-phosphorus.

15P30 which is radioactive with a half life about 3 minutes, decays to a stable isotope of silicon by emitting a positron (positive electron) which has the same mass as electron, but positive charge.

Curie Joliot and her husband Frederick. Joliot were the first to discover induced radioactivity in 1934. They were awarded 1934. Nobel prize in chemistry. They bombarded elements aluminium and boron with a particles. They observed that the targets continued to emit radiations even after the removal of the a source. The radiations consisted of positrons.

Nature of Radioactive radiations for std 8 to 10 science

NATURE OF RADIOACTIVE RADIATIONS
Rutherford, a British physicist and others studied the nature of radioactive radiations, in 1898. They found that the radiations can be classified into three distinct types.
They named these three types as

alpha (a) rays, 

bata (b ) rays and 
gamms (g) rays.

Experiments show that
a-rays consist of positively charged particles,
B-rays consist of negatively charged particles (steam of electrons) and
y-rays (energy) are electrically neutral.
All radioactive atoms emit either a-rays or B-rays, never both,
and this may be accompanied by y-rays.
Alpha rays( or a-particles) are nothing but helium nuclei, i.e.
an a-particle consists of 2 protons and 2 neutrons bound to together.
Beta rays are electrons, identical to those that orbit the nucleus. But they are created within the nucleus. Gamma rays are high energy photons whose energy is higher then that of X-rays.

TRANSMUTATION 

When a radioactive nucleus emits an a-particle, the remaining nucleus will be different from the original because there is loss of two protons and two neutrons. For example, radium 226 (A=226, Z=88) is an a. emitter. It changes (decays) to a nucleus with z=(88-2)=86 and A=(226-4)=222. The new nucleus is radon (Rn).

Note :

To specify a given nucleus (or nuclide), we need to give only A and Z, where A represents the mass number, sum of the numbers of protons and neutrons and Z represents the atomic number the proton number, (A-Z) being neutron number.
A nucleus X with mass number A and atomic number, Z is represented by the symbol zXA 
Radium 226 is represented as 88Ra225..

The original nucleus is called parent nucleus and the new nucleus is Called daughter nucleus. The changing of one element into another is known as transmutation.
The transmutation of radium 226 into radon 222 can be written as
 88Ra226 --- > 86Rn222
Transmutation also occurs when a nucleus decays with the emission of a b particle. For example, Carbon-14 decays with the emission of a B particle; this can be written as
 6C14 --- > 7N14
During b decay it is assumed that a neutron in a nucleus changes to a proton and an electron. Newly formed electron is emitted and proton remains in the nucleus. This is how Z increases by 1.

HALF-LIFE 

Theoretically, the decay process of a radioactive element in never complete and there is always some residual radioactivity. In other words, time taken for all the atoms to disintegrate, is infinite. For this reason, the half-life of a radioactive element is considered. Half-life of a radioactive element is defined as the time taken by a radioactive sample of that element, to get reduced to half its initial amount. Half-life is useful in comparing the activities of different radioactive elements. Half-life varies from micro seconds to billions of years.
Half –life is found to be a characteristic feature of a radioactive element. Half-life is represented by T/2. If a sample of radioactive element contains N nuclei at a time (taken as Zero), then after a time equal to half –life, the number reduces to N/2; during the next half life that is after two half-lives N/4 and after three half-lives N/8 and so on. This is represented in a graph. 

Half-Life of a radioactive element

For example half-life of radium-226 is about 1600 years. Suppose we start with1 mg of radium, In 1600 years it reduces to 0.5 mg, 0.25 mg in 3200 yrs. 0.125 mg in 4800 years and so on.

Half life of Polonium 214 is only 164 m s (m s = micro second = 10-6S). Half-life of uranium 238 is 4.5 billion years which accounts for its presence in nature. The half life of radium is 1622 yrs and the 200 mg sample of Radium separated by the Curies in 1898 now contains about 190 mg. 

more details:

Radioactivity elements radiations isotopes for std 8 to 10

http://simplewayoflearnphysics.blogspot.in/2012/05/radioactivity-elements-radiations.html

Radioactivity elements radiations isotopes for std 8 to 10

REVIEW
You have learnt the following earlier, recall them.
An atom is made up of three fundamental particles namely proton, neutron and electron.
Protons and neutrons are bound together is the central part of an atom, called the nucleus.
Electrons revolve round the nucleus in different imaginary orbits.
The number of protons in an atom is called its atomic number, represented by Z.
Protons and neutrons is a nucleus have a common name ‘nucleons’ the total number of nucleons in an atom is known as the atomic mass number represented by A. Mass number is very close to the atomic mass.
Electron (-1eo) is a negatively charged particle with negligible mass.
Proton (+1p1) is a positively charged particle with unit mass considering the mass of hydrogen atom to be ‘one unit’.
Neutron (0N1) is an electrically neutral particle with unit mass.

INTRODUCTION 

In 1896, Henri Becquerel (1852-1908) a French scientist, accidentally discovered radioactivity. He found that a photographic plate, wrapped well to protect is from visible light, was blackened by a mineral containing uranium. He concluded that the mineral emitted a new kind of radiations which occurred without any external cause. The emission of these radiations is not affected by external factors like temperature, pressure, electric field and magnetic field. The radiations were called Becquerel rays.

Radioactivity 

All elements which emit Becquerel rays are said to be radioactive and the elements are called radioactive elements.
All the elements from atomic number 81 to 92 are found to be radioactive. Experiments show that atoms of radioactive elements disintegrate into atoms of other elements. It became clear that the radiations must emanate from the nucleus and radioactivity is a nucler phenomenon. We can conclude that the phenomenon is due to disintegration of an ustable nucleus accompanied by some type of radiation.
The property of spontaneous disintegration of certain unstable. This is referred to as natural radioactivity. Radioactivity produced artificially or induced, is called artificial or induced radioactivity. The radiations emitted by radioactive elements are called radioactive radiations.
In 1898, Marie Curie (1867-1934) and her husband Pierre Cune (1959-1906) discovered a new element named Polonium and later on, another element named Radium, In 1903 Nobel prize in physics was shared by H. Becquerel, M. Curie and P. Curie, for their discovery of radioactivity. In 1911, M. Curie was awarded Nobel prize in chemistry for the extraction of radium in its purest form.