10th Physical Sciences Model Questions – Page 2

Q: How do the values of electron gain enthalpy change in a group, in a period and in metals? (2 Marks)

A: Electron gain enthalpy values decrease as we go down in a group, but increase along a period from left to right.
Metals have very low electron gain enthalpy values and alkaline earth
metals have even positive values.
Note that the negative sign for energy value in table indicates that energy is liberated or lost, and the positive sign tells that the energy is gained or absorbed.
All the factors which influence the ionization energy would also influence the electron gain enthalpy.

Q: Explain the term ‘electronegativity’. What factors influence it?

A: The electronegativity of an element is defined as the relative tendency of its atom to attract electrons towards it self when it is bonded to the atom of another element.
All the factors that influence the ionization energy and the electron affinity of elements influence the electronegativity values of these elements.
Because of this, Millikon proposed that the electronegativity of an element is the average value of its ionization energy and electron affinity.
Electronegativity = Ionization energy + electron affinity / 2

Q: How does the value of electronegativity vary as we go down a group or across a period? (2 Marks)

A: Electronegativity values of elements decrease as we go down in a group and increase along a period from left to right.
The most electronegative element is ‘F’. and the least electronegative stable element is ‘Cs’.

Q: Write a note on the properties of ‘metals’ and ‘non – metals’. (4 Marks)

A: Metals generally show less electronegative character. In compounds, they generally show a tendency to remain as positive ions.
This property is often termed as electropositive character. Metals are electropositive elements.
Non metals are generally more electronegative due to their smaller atomic radii.
Let us examine the elements of 3rd period.
3rd period: Na Mg Al Si P S Cl.
We know that Na and Mg are metals; Al and Si are semi metals (metalloids); P, S and Cl are non metals. So we find metals on left side and non metals on right side of the periodic table.
This metallic character decreases while non metallic character increases as we move along a period (from left to right)

Let us take group 14 (IV A) elements.
IV A group: C Si Ge Sn Pb
Here also we know that carbon is non metal, Si and Ge are metalloids, Sn and Pb are metals.
So we find non metals particularly at the right hand side top and metals at the left and right hand side bottom of the periodic table.
This means metallic character increases while non metallic character
decreases in a group as we move from top to bottom.

Question: What is the action of soap particles on greasy cloth? (4 Marks)

Answer: Soaps and detergents make oil and dirt present on the cloth come out into water, there by making the cloth clean.
a) Soap has one polar end and one non-polar end.
b) The polar end is hydrophilic in nature and this end is attracted towards water.
c) The non-polar end is hydrophobic, in nature and it is attracted towards grease or oil on the cloth, but not attracted towards water.
d) When soap is dissolved in water, its hydrophobic ends attach themselves to dirt and remove it from the cloth.
e) The hydrophobic end of the soap molecules move towards the dirt or grease particles.
f) The hydrophobic ends attached to the dirt particle and try to pull out.
g) The molecules of soap surround the dirt particle at the centre of the cluster and form a spherical structure called micelle.
h) These micelles remain suspended in water like particles in a collidal solution.
i) The various micelles present in water do not come together to form a precipitate as each micelle repells the other because of the ion- ion- repulsion.
j) Thus, the dust particles remain trapped in micelles and are easily rinsed away with water.
k) Hence, soap micelles remove dirt by dissolving in water.

Question:

We know metals are arranged basing on their reactivity. What is the name given to that arrangement? How it helps in extraction of metals? (4 Marks)

Answer: Activity Series: Extraction of the metal from its ore depends on the reactivity of the metal.
a) To understand the order of reactivity of metals that are very familiar, we study their chemical reactions with cold water, steam, dilute, strong acids and Cl2 and based on their vigorous activity order in these reactions, we frame out activity series.
b) Arrangement of the metals in decreasing order of their reactivity is known as activity series. Usefulness of activity series in extraction of metals:
c) Simple chemical reduction methods like heating with C, Co etc., to reduce the ores of these metals depends mainly on the position of the metal in the activity series.
d) Extration of metals at the top of the activity series can be done by electrolysis.
e) Extraction of metals in the middle of the activity series can be extracted by
1)) Sulphide ores are converted into oxides by roasting.
2) The metal oxides are then reduced to the corresponding metal by using suitable reducing agents like carbon.
f) Extraction of metals at the bottom of the acitivity series by heating alone as they are often found in free state.
g) Extraction of these metals can also be done by displacement from aqueous solutions.

Question:

How do you appreciate the role of Buckminister fullerence in medicine. (2 Marks)

Answer: Fullerences are under study for potential medicinal use such as specific antibiotics to target resistant bacteria and even target certain cancer cells such as melonoma.
a) This is still under research studies.
b) I appreciate its usefulness in medicine which may become a good medicine for curing certain cancer in the time to come.

Question:

What is the role of esters in everyday life? (2 Marks)

Answer: Esters are generally volatile liquids with sweet or pleasent smell or fruity smell.
a) Artificial perfumes are made with esters.
b) Esters are used as flavouring agents.
c) Esters are used in making artificial flavours and essences used in ice-creams, sweets, cool drinks… etc.,
d) Saponification (soap making) is the alkaline hydrolysis of esters.

10th Class Physics Important Questions – Elements Chapter – For AP and Telangana

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