science preparatory 2 Final revision

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science preparatory 2 First Term 

[1]Give reasons with answers 2023

1 -Many attempts are made by scientists for classification of elements.

– To be easily studied and to find the relation between elements and their physical and <a href="">chemical</a> properties.

2 – Failure of Mendeleev’s periodic table (Appearance of Mosley’s periodic table).

Because there were some disadvantages such as:

A- Make disturbance in the ascending order of atomic weights for some elements.

B- Dealing with isotopes of one element as different elements.

3 -Mosley arranged the elements according to their <a href="">atomic number</a> not their atomic weight.

Because he found that the periodicity of the elements properties is related to their atomic numbers not their atomic weight.

4 -Element (11Na) lies in the first group, while element (13 Al) lies in the third group.

Because the no. of <a href="">electrons</a> in the outer most shell for (Na) = 1

And the no. of <a href="">electrons</a> in the outer most shell for (Al) = 3

5 – Knowing the <a href="">atomic number</a> for the element allowing determining its location in the periodic table.

Because number of <a href="">energy</a> levels indicates the period, while number of outer most <a href="">electrons</a> indicates the group.

6 – The atomic size decreases in the period by the increase of the <a href="">atomic number</a>.

– Due the increase of the attraction force between positive nucleus and the <a href="">electrons</a> in the outermost <a href="">energy</a> level.

7 -The atomic size increases in the same group by the increase of their atomic numbers.

– Due to the increase in the number of <a href="">energy</a> levels in the <a href="">atom</a>.

9 -water and ammonia are polar compounds.

Because the electronegativity difference between their elements is relatively high.

11 -It is difficult to identify semimetals by knowing their electronic configuration.

Due to the difference of numbers of the <a href="">electrons</a> in their valence shells.

12 -Metallic property of the same group increases by the increase of the <a href="">atomic number</a> as we go from up to down.

Due to the increase of the atomic size.

13 -Non-metallic property decreases in the group as in (7A).

Due to the decrease of electronegativity values.


15 -The metals of group (1A) are called alkali metals.

Because they react with water forming alkali solutions.

16 -Although Hydrogen gas exists in group (1A) it is a non-metal.

Because its <a href="">atom</a> is remarkably small and it is a gaseous element.

17 – Some of alkali metals are kept under kerosene or paraffin.

To prevent their reaction with moist air.

18 – Lithium is kept under Paraffin not kerosene.

Because it floats on the surface of kerosene and it is immediately burns.

19 -water which used in the cooling of the nuclear reactors destroys the marine organisms found in it.

Due to the separation of the dissolved oxygen in it.

20 – Alkali metals are monovalent elements.

     Because they contains one electron in the outer most <a href="">energy</a> level.

21 -Earth alkaline metals are divalent elements.

Because they contains two <a href="">electrons</a> in the outer most <a href="">energy</a> level.

23 -the <a href="">chemical</a> activity of group 2A elements increases by the increase of the atomic size.

Because the loss of valency <a href="">electrons</a> become easier.

24 -elements of group (17) are called Halogens.

   Because they react with metals forming salts.

    2K + Br2                                   2 KBr

26 -elements of group (17) are monovalent elements.

Because they gain one electron during the <a href="">chemical</a> reactions

27 -elements of group 17 don’t exist individually.

Because they are chemically active.

28 -Sodium is used in its liquid state as it is a good conductor of heat.

Because it is used in the transferring heat from inside the nuclear reactor to outside.

29 -Silicon slides are used in the manufactures of computers .

Because they are semiconductors which their conductivity of electricity depends on the temperature.

30 -Liquified Nitrogen is used in the preservation of cornea.

Because it has a very low boiling point (-196° c).

31 -The radioactive cobalt is used in food preservation.

Because gamma rays which comes out from it prevent the reproduction of microbial cells.

32 -A weak electrostatic attraction originated between water molecules which are called hydrogen bonds.

Due to the large electronegativity of oxygen compared with hydrogen.

33 -The abnormality of water properties.

Because of the presence of hydrogen bonds between its molecules.

34 -water is a unique substance.

Because its existence in the three states at the ordinary temperature.

35 -Rising of the boiling point of water.

Due to the presence of hydrogen bonds.

36 -The density of water when it is in solid state is lower than when it is a liquid state.

Because when it is in the temperature lower than 4 ° c, the water molecules are collected by hydrogen bonds forming hexagonal crystals with many spaces between them.

37 -Swimming in the sea is easier than swimming in the pole.

Because the density of salty water is higher than density of the fresh water.

40 -water is neutral liquid.

Because when it is ionizes it gives equal numbers of positive hydrogen ions and negative hydroxide ions. (H+ = OH -).

41 -Mixing human and animal wastes of water cause many diseases.

Because it cause the biological pollution which makes (Bilharzia – typhoid – hepatitis)

42 -Importance of aneroid barometer.

To estimate the day weather and atmospheric barometer.

43 -Troposphere is called disturbed layer.

Because most of the weather changes takes place in it.

44 -All atmospheric phenomena like rains, winds and clouds takes place in troposphere.

Because it contains about 75% of the atmosphere <a href="">mass</a>.

45 -Earth’s atmosphere is organized by the 1st atmospheric layer (troposphere).

    Because it contains about 99%of the atmospheric water vapour.

46 -At the lower part of the stratosphere, the temperature measures (– 60º C), then increases gradually until it reaches 0º C at the end of the layer.

Due to the absorption of ultraviolet <a href="">radiation</a> (emitted from The Sun) by the ozone layer that is present in the upper part of the layer.

47 -The lower part of stratosphere is suitable for flying planes.

Because it doesn’t contain clouds or any weather disturbances and the air moves in this part horizontally.

48 -Although meteors burn in the mesosphere, space ships don’t burn during passing through it.

As they have a conical front that disperses heat and tails made of an insulated material.

49 – Mesosphere layer is much vacuumed.

As it contains only a limited amount of <a href="">helium</a> and hydrogen gases.

50 – Meteors burn in mesosphere layer.

Due to friction with air molecules.

51 – Thermosphere means the heated layer.

As it is the hottest layer of the atmosphere.

52 – Ionosphere plays an important role in wireless communication and broadcasting.

As it reflects radio waves that are transmitted by communication centers and radio stations.

53 – Ionosphere is surrounded by two magnetic belts known as Van Allen Belts.

Because these two belts scatter  harmful charged cosmic <a href="">radiation</a> away from the Earth.

54 – Ozone layer is formed in the stratosphere.

Because it contains a suitable amount of oxygen gas.

55 -Important of ozone layer (Ozone is said to act as a protective shield for living organisms).

Because it does not allow penetration of all far and medium ultraviolet radiations, which have very harmful effects.

56 -Ultraviolet radiations, of wavelength close to the visible light penetrate the atmosphere and reach the earth’s surface.

Where it helps in producing Vitamin D in the bodies of the newly born babies.

57 -Ozone Hole increases in September each year.

Because all pollutants are assemble as black clouds that are pushed by the wind towards South Pole.

58 -Use of chlorofluorocarbon compounds must be reduced.

Because they erode the ozone layer.

59 -stop producing the ultrasound concord planes.

Because their exhausts affects the ozone

60 -The temperature of the planet earth has been increased.

Due to the greenhouse gases in the atmosphere.

62 -Altimeter is used in airplanes.

To determine the elevation of navigation based on the atmospheric pressure.

63 -The difference between cast and mold fossils.

Cast: gives the internal details of the living.

Mold: Gives the outer details of the living.

64 -The importance of the index fossil.    

It indicates the age of sedimentary rocks and help in petroleum exploraton

[2]What Is The Function Of The Following?

1- Bohr:



4-Modern Periodic Table:

5-Liquified Sodium:

6-Cobalt 60:


10-Hydrogen Bond:

11-Low Density during Water Freezing:

14-Hofmann S Voltmeter:








22-Van-Allen Belts:

23-Ozone Layer:

24-Dobson Unit:

25-Barometer Instrument:

26-Aneroid Device:

27-Map of Atmospheric Pressure:

28-Altimeter Set:

29-Freon (Chlorofluorocarbon) (CFC):


31-Methyl Bromide Gas:

32-Montreal Protocol:

33-Kyoto Protocol:


35-Coral Fossils:

36-Nummulite Fossils:

37-Ferns Fossils:

38-Snow & Amber:

39-Natural Protectorate:

40-Horns of Rhinoceros:

41-Bluestone Protectorate:

42-Panda Protectorate:

43-Ras Mohamed Protectorate:

44-Wadi-Hetan Protectorate:

45-(IUCN) Society:




[3] Problems of atmospheric pressure:

1) Temp. At top = temp. At down – (height × 6.5)

2) Temp. At down = temp. At top + (height × 6.5 )

3) Height = temp. at down – temp. at top /6.5

1- Find the temperature at a point of height 10000 meters above sea level if the temperature at sea level is 24°C.

2- Find the temperature at a point of height 2000 meters above sea level if the temperature at sea level is 23°C.

3- If the temperature at sea level is 24.5°C, find the temperature at the top of troposphere layer if its thickness is 13 kilometers.

4- Calculate the height of a mountain if the temperature at its base is 30°C and at its top is (— 9°C).


1- lithum and sodium ……. On the surface of water  as their densities are …. than water density.

2-water is a good polar …….. as it has the ability to dissolve most ……. Compounds

3-……. Is the second atmosphere layer and it is also called the…….

4-…….. is surrounded by two magnetic belts known as ……

5-In Moseley s periodic table the <a href="">atomic number</a> of each element increases by ……… from the element before it in the same …………..

6-…….. trees secrete resinous matter which changes into …….. after solidification.

7- ……. Are safe areas established to protect endangered <a href="">species</a> in their homeland.

8-……….. originated from mixing of human and animal wastes with water causing many diseases .

9- The scientist ……………. Discovered the main <a href="">energy</a> levels

10-The …………. is the unit used to measure the atomic size .

11- MgO + H2O                        ……………….

12- The bond between oxygen and hydrogen in water molecule is …………..

13-The layer of atmosphere which contains ozone layer is called ………..

14-The main cause of extinction of Dodo bird is ………….

15-The d-block contains ……… elements .

16- 2H2O                          ………….. + …………………… 

17-Magnesium reacts with hydrochloric acid giving ………… and …………….

18-increasing the concentration of mercury in drinking water causes ………. While …………..increases the infection rate by liver cancer.

19-The measuring unit of atomic size …………

20-The satellite revolve around the earth in a region called ………….

21- ………….. has a wolf s , head ,dog s tail and tiger s skin

22-The modern periodic table consist of ………. Horizontal  periods and …….. vertical groups.

[5] Compare between :

1-Elements of group  1A   , 2A  related to (Name- valency – density – kind of ions)

2-mesospher and troposphere in terms of temperature and structure

3- mammoth and amber fossil

4-Altimeter and aneroid

5-Cathode and anode in Hofmann s  voltameter (the type of evolved gas at the 2 poles)

6- Moseley s P.T and Mendeleev s  P.T (concepts of arrangement elements)

7-troposphere and stratosphere( temp, pressure )

8-Thermosphere and mesosphere (height – temp)

[6]Locate the position of an element its <a href="">atomic number</a> is 17 then:

a-find the <a href="">atomic number</a> above it in the same group

b-write the name of the group in which both of them are present

[7] what is the importance ?

1-foraminifera fossil

2-silicon element

3-Liquified Sodium:

4-Cobalt 60:


6-Hydrogen Bond:

7-Hofmann S Voltmeter:


9-Van-Allen Belts:

10-Ozone Layer:

11-Dobson Unit:

12-Barometer Instrument:

13-Aneroid Device:

14-Map of Atmospheric Pressure:

15-Altimeter Set:

16-Freon (Chlorofluorocarbon) (CFC):


18-Methyl Bromide Gas:

19-Montreal Protocol:

20-Kyoto Protocol:


22-Coral Fossils:

23-Nummulite Fossils:

24-Ferns Fossils:

25-Natural Protectorate:

26-Horns of Rhinoceros:

27-Bluestone Protectorate:

28-Panda Protectorate:

29-Ras Mohamed Protectorate:

30-Wadi-Hetan Protectorate:



[8] How can you explain:

  1. Presence of Nummulite fossils in desert environment
  2. Occurrence of Aurora phenomenon
  3. Atomic size increases from up to down in the group
  4. Cutting tress may lead to global warming

[9]What happens when ?

  1. Sorting water in plastic bottles
  2. Increasing the ratio of greenhouse gases in atmosphere
  3. The temperature of water becomes less than 4
  4. The harmful ultraviolet rays affect the human
  5. Adding dil HCL to a piece of <a href="">copper</a>
  6. Dipping old <a href="">insects</a> in amber
  7. Decrease of water temperature to 4 c
  8. Dissolving magnesium oxide in water (write the balanced equation)
  9. Melting of ice of both poles
  10. Increasing the ratio of nitrogen oxides in the atmosphere
  11. Passing of electric current through Hofmmans  voltameter containing acidic water
  12. Throwing detergents in water
  13. -The low rate of reproduction of passenger pigeon 

[10]Mention the difference  between

  1. the cast and the trace
  2. the simple ecosystem and the complicated ecosystem
  3. traces and remains
  4. near and far ultraviolet rays
  5. basic oxides and acidic oxides
  6. fluorine molecule and <a href="">helium</a> molecule

[11] mention an example ?

1-A very active metal    

2-an endangered animal

3-An extinct animal

4-polar compound

5-fossils of complete body

 6-chemical water pollutants

7-greenhouse gases

8-basic oxide

9- an element that has the highest electronegativity

10-An animal habitats bamboo forests

11-A microscopic fossil

12-An endangered bird

13-A pollutant of ozone layer

14- a metalloid element

[12]Choose the odd word out then mention what the rest has in common:

1-methyl bromide – Halons – nitrogen oxides – carbon dioxide

  • mesopause – stratopause – stratosphere – tropopause
  • Trilobite fossils – nummulites fossils – fossils of <a href="">ferns</a> – Ammounites fossils

[13]What is the results of each of the following ?

  1. Absence of ozone layer
  2. Burning of magnesium strip in the presence of o2 gas (show by equation)

[14]Explain the behavior of water with

  1. Iron
  2. potassium
  3. Sodium
  4. Zinc

[15]Write short notes about each of the following:

  1. Reasons of recent extinction
  2. Different types of ecosystem with examples

[16]What are the consequence of the following :

1-the pollution of water with animals and human wastes

2-Mineral salts replace the organic matter of dinosaurs eggs

17)Problem:Element Y18 in a periodic table find:

1-Its electronic configuration  2- its group  3- its period

2-locate the position (group – period –block) of element 7X and find the <a href="">atomic number</a> of the element follows this element in the same group

3-if the temp. at the foot of mountain is 35 c  find the temp. at height 300 m above the earths surface

4-calculate the height of a mountain if the temperature at it foot is 20 c  and its top is -6c

5-Illustrate with fornula  only the role of ultraviolet in formation of ozone gas

18)What is meant by  (define )?

1- Electronegativity:

The ability of the <a href="">atom</a> in covalent molecule to attract the <a href="">electrons</a> of the bond towards itself.

2- Polar compound:

They are covalent compounds in which the difference in electronegativity between elements forming their molecules is relatively high.

4- <a href="">Chemical</a> activity series:

series in which metals are arranged in a descending order according to their <a href="">chemical</a> activity.

5- Hydrogen bond:

Weak electrostatic attraction force that arises between the molecules of polar compounds.

10- Hofmann’s voltammeter:

An apparatus used for the electrolysis of acidified water.

11- Water pollution:

The addition of any substance to the water which causes continuous gradual change in water properties and affecting the health and the life of living creatures.

12- Metalloids [Semi – metallic elements]:

They are elements which have the properties of both metals and non metals.

13- Atmospheric envelope of earth:

It is gaseous envelope rotating with the Earth around its axis and it extends about 1000 km above sea level.

14- Atmospheric pressure:

The weight of air column of an atmosphere height on a unit area (1 cm2 or 1 m2)

16- Isobar:

curved lines that join the points of equal pressure in atmospheric pressure maps.

17- Tropopause:

The region between troposphere and stratosphere.

18- Stratopause:

The region between stratosphere and mesosphere.

19- Mesopause:

The region between mesosphere and thermosphere.

20- Ionosphere layer:

The layer that contains charged ions and it has an important role in wireless communications.

21- Van Allen belts:

They are two magnetic belts surrounding ionosphere and play an important role in scattering of harmful charged cosmic radiations.

22- Aurora phenomenon:

A phenomenon that appears as brightly coloured light curtains seen from the both poles (North and south) of the Earth.

23- Exosphere:

Region in which the atmospheric envelope is inserted with outer space.

24- Erosion of ozone layer:

Losing parts of ozone layer (become thin).

25- Global warming phenomenon:

Continuous increase in the average temperature of the earth near surface air.

26- Green house effect: T

rapping of infrared <a href="">radiation</a> in the troposphere layer due to increase of ratio of greenhouse gases which cause the increase of planet Earth temperature.

27- Fossils:

They are traces and remains of the old living organisms that are preserved in sedimentary rocks.

28- Trace:

They are traces indicate the activity of once an old living organisms during its life.

29- Remains:

They are parts indicate the remains of once old living organisms after death.

30- Amber:

The resinous mater is secreted from pine trees and had been solidified and preserved the bodies of organisms from decaying.

31-  Solid cast:

It is replica of the internal details of a skeleton of once an old living organism.

32-  Mold: It is replica of the external details of a skeleton of once an old living organism.

33- Petrified fossils:

They are fossils in which minerals replace the organic matter for organism part by part leaving the shape without any change.

34- Petrified woods:

They are fossils which are formed as a result of replacing the organic matter of wood by silica part by part and they give us details about the life of once an old plant.

35- Petrification:

It is the process of replacing wood material of trees by silica to form petrified woods part by par.

36- Index fossils:

They are fossils of the organisms that lived a short period of time in the past and had a wide geological distribution and became extinct.

37- Fossil record:

The fossils that exist in the rocks of different areas that indicate the extinction and evolution of organisms.

38- Extinction:

It the continuous decrease without compensation in the number of a certain <a href="">species</a> of living organisms until all members dies out.

39- The moment of extinction:

It is the date of death of last individual of that <a href="">species</a>.

40- IUCN:

The International Union for Conservation of Nature, was established to protect the endangered <a href="">species</a>.

42- The simple ecosystem:

It is ecosystem that has a few members and it is affected by the absence of one type of <a href="">species</a> of organisms.

43- The complicated ecosystem:

It is ecosystem that has multiple members and it is not affected much by the

absence of a <a href="">species</a> of the living organisms.

45- Natural protectorates:

They are safe areas established to protect endangered <a href="">species</a> in their homeland.

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