Class 8 General Science Chapter 5 Inside the Atom l Exercise

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General Science -  8th Standard   

5. Inside the Atom

Question & Answer

 

1. Answer the following.

a. What is the difference in the atomic models of Thomson and Rutherford?

Ans:

Thomson Theory	Rutherford Theory
States that electron are embedded in a positively charged solid material which is spherical in shape	States that an atom is composed of an atomic nucleus around which electrons are revolving in an orbit
Does not give any detail about the atomic nucleus	Explains about the atomic nucleus
States that electrons are uniformally distributed in an atom	States that electrons are located around a central solid material
Indicates that atom is spherical in shape	Indicates that an atom has a central solid core called as nucleus surrounded by the electrons
Does not give any idea about constituents of nucleus	States that nucleus is composed of protons and neutrons

 

b. What is meant by valency of an element? What is the relationship between the number of valence electron and valency?

Ans: Valency of an element : It is the number of electrons of an atom of the element uses to combine with atoms of other elements.
It is the combining power of an atom of the element.
Valency of an atom is determined by its electronic configuration.
It gives idea about the number of electrons loss or gain in order to achieve the nearest noble gas configuration.
For example: Na(11) = 2,8,1 So, its valency is 1
                      Cl(17) = 2,8,7 So, its valency is also 1

Number of valence electron : It is defined as the number of electrons present in the outermost shell of an atom.
It is not necessary that all the valence electrons take part in bonding.
For example: Na(11) = 2,8,1 So, its number of valence electron is 1

Cl(17) = 2,8,7 So its number of valence electron is 7

It can be seen that valency of an element is related to number of valence electrons in that atom.

c. What is meant by atomic mass number ? Explain how the atomic number and mass number of carbon are 6 and 12 respectively.

Ans: Atomic Mass Number : It is the sum of total number of protons and neutrons present in a nucleus.
Atomic mass number = number of protons + number of neutrons.
Atomic number = number of protons = number of electrons. It is denoted by Z.
Mass number = number of protons + number of neutrons. It is denoted by A.
For example : Carbon atom its, Number of proton = 6
                           Number of neutrons = 6
                           Number of electron = 6

Atomic number(Z) = number of protons = number of electrons = 6.
Mass number(A) = number of proton + number of neutrons = 6 + 6 =12.

d. What is meant by subatomic particle ? Give brief information of three subatomic particles with reference to electrical charge, mass and location.

Ans: Subatomic particles : A subatomic particle is a structural and functional unit of the matter. That means all the matters are made up of these fundamental particles. According to modern atomic theory, an atom has a nucleus, which is present in its center or core. These nucleus contain subatomic particles like protons and neutrons.
Difference between subatomic particles are as follows :

Electron
1. Electrons are present outside the nucleus of an atom.
2. Electrons are negatively charged that is (1.6 × 10⁻¹⁹coulomb).
3. The mass of an electron is considered to negligible. It is 1800  times less than that of a hydrogen
4.Relative mass = 1/ 1840 times hydrogen
5. It revolves around the nucleus in the discrete orbit.

Proton
1. Protons are present in the nucleus of an atom.
2. Protons are positively charged that is (1.6 × 10⁻¹⁹coulomb).
3. The mass of a proton is approximately 1u(1Dalton) that is (1u = 1.66 × 10⁻²⁷ g).
4. They are closely bound in the nucleus.

Neutron
1. Neutrons are present in the nucleus of an atom.
2. Neutrons are neutral.There is no charge.
3. The mass of a neutron is nearly equal to the mass of a proton that is 1u(1Dalton) that is (1u = 1.66 × 10⁻²⁷ g).
4. They are closely bound in the nucleus.

2. Give scientific reasons.

a. All the mass of an atom is concentrated in the nucleus.

Ans: All the mass of an atom is concentrated in the nucleus because atom contains three subatomic particles like electron, proton and neutron.Out of which, nucleus present at the centre of an atom contains two subatomic particles that's protons and neutrons and the mass of nucleus is the sum of mass of protons and neutrons located at the centre of an atom.

b. Atom is electrically neutral.

Ans: .Atom is electrically neutral because in an atom electrons and protons carry charges and each atom has equal numbers of protons (positively charged) and electrons (negatively charged).

c. Atomic mass number is a whole number.

Ans: Atomic mass number is a whole number because it is the sum of numbers of protons and numbers of neutrons present in an atom.Which is present in the form of integers.

d. Atoms are stable though negatively charged electron are revolving within it.

Ans: Atoms are stables though negatively charged electrons are revolving within it because each atom contains equal numbers of protons and electrons. So, charge on negatively charged electrons are balanced by charge on positively charged proton. Therefore, atom is electrically neutral and stable. 

3. Define the following terms

a. Atom

Ans: An atom is defined as  the structural and functional unit of a matter. The term "atom" comes from the Greek word which means indivisible, because atoms are the smallest things in the universe and could not be divided. atoms are made up of three subatomic particles like protons, neutrons and electrons.

b. Isotope

Ans: Isotopes are atoms that have same atomic number but different mass number. Isotopes have same numbers of protons but different numbers of neutrons.
These are some common examples of isotopes: 3
2He, 4
2He, 12
6C, 14
6C, 235
92U, 239
92U, 289.

c. Atomic number

Ans: The number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table. Atomic number is also equal to numbers of electrons in an atom.
For example :
Atomic number of carbon = 6
Atomic number of nitrogen = 7
Atomic number of oxygen = 8
Atomic number of magnesium = 12

d. Atomic mass number

Ans: It is the sum of total number of protons and neutrons present in a nucleus.
atomic mass number = number of protons + number of neutrons.
Atomic number = number of protons = number of electrons.It is denoted by Z.
Mass number = number of protons + number of neutrons. It is denoted by A.
For example : Carbon atom its, Number of proton = 6
                           Number of neutrons = 6
                           Number of electron = 6
Atomic number (Z) = number of protons = number of electrons = 6
Mass number (A) = number of proton + number of neutrons = 6 + 6 =12

 

e. Moderator in nuclear reactor

Ans: Moderator in nuclear reactor: Moderator of a nuclear reactor is a substance that slows down the speed of neutrons. In traditional nuclear reactors, the moderator is the same thing as that of coolant like water.

4. Draw a neat labelled diagram.

a. Ruthrford's scattering experiment

Ans:

 

 

b. Thomson's atomic model

Ans: 

c. Diagramatic sketch of electronic configuration of Magnesium (Atomic number 12)

Ans:

 

d. Diagramatic sketch of electronic configuration of Argon (Atomic number 18)

Ans:

 

5. Fill in the blanks.

a. Electron, proton, neutron are the types of subatomic particles in an atom.

b. An electron carries a negative charge.

c. The electron shell K is nearest to the nucleus.

d. The electronic configuration of magnesium is 2, 8, 2. From this it is understood that the valence shell of Magnesium is M shell.

e. The valency of hydrogen is 'one' as per the molecular formula H2O. Therefore valency of 'Fe' turns out to be three as per the formula Fe2O3.

6. Match the pairs.

Group ‘A’	Group ‘B’ (Ans)
Proton	Positively charged
Electron	Negatively charged
Neutron	Neutral

 

7. Deduce from the datum provided.

 

Ans:

 

Class 8 General Science Chapter 2 Health and Diseases l Exercise

 YADNYA e-Learning

General Science -  8th Standard   

                        2. Health and Diseases

Question & Answer

 

1. Distinguish between- Infectious and non-infectious diseases.

Ans:

Infectious diseases	Non-infectious diseases
It can be passed from one person to another.	It cannot be passed from one person to another.
It is caused by a pathogen.	It is caused due to internal reasons like metabolic or genetic reasons.
They are classified as communicable disease.	They are classified as non communicable disease.
eg: diarrhoea, cholera, tuberculosis	eg: diabetes, hypertension, cancer

 

2. Identify the odd term.

a. Malaria, hepatitis, elephantiasis, dengue.

Ans: Hepatitis is the odd one out because it is a type of viral infection while the rest of three are spread through the bite of mosquitoes.

 

b. Plague, AIDS, cholera, T.B.

Ans: AIDS is the odd one out because it is a viral disease while the rest of them are bacterial diseases.

 

3. Answer in one to two sentences.

a. Which are various media of spreading the infectious diseases?

Ans:  Infectious diseases can spread through air, water, blood to blood contact and animal vectors.

b. Give the names of five non-infectious diseases other than given in the lesson.

Ans: Non infectious diseases- arthiritis, cataract, osteoprosis, multiple sclerosis and Alzeimer's.

 

c. Which are the main reasons of diabetes and heart diseases?

Ans: Reasons of heart diseases include smoking, alcoholism, diabetes, hypertension, obesity, lack of physical exercise, mental stress, anxiety and improper diet.

Reasons of diabetes include obesity, lack of physical exercise, mental stress, improper diet and hereditary.

 

4. What can be achieved / can be prevented?

a. Drinking boiled and filtered water.

Ans: Boiling and filteration are methods of purifying water which makes it suitable for consumption. Drinking boiled and filtered water can help in prevention of water borne diseases such as typhoid, cholera, etc. Most of the water borne diseases are transmitted through the consumption of contaminated water in some or the other form. 

 

b. Avoiding smoking and alcoholism.

Ans: Smoking and alcoholism are two of the devils of our health and society. Smoking leads to various kinds of respiratory disorders and hinders the process of respiration. It can lead to diseases such as lung cancer. On the other hand, consumption of alcohol, effects the nervous as well as the digestive system of our body. Avoiding alcohol and smoking can protect individuals from various diseases and can help in living a healthy and stress free life.

 

c. Regular balanced diet and exercise.

Ans: Balanced diet and exercise are key to good health. Both of these in combination helps our systems to function properly, helps maintain a healthy weight, reduces body fat, provides the body with energy, promotes good sleep and makes us feel better about ourselves.

 

d. Proper checking of blood before blood donation.

Ans: Proper checking of blood before blood donation is required to check that the blood to be transferred is safe in all respects. There are chances of transfer of infectious diseases form the donor, if he/she is suffering from any such diseases. Another important factor for checking of blood before donation is to check that the donor is not anemic (does not have anemia). 

 

5. Read the passage and answer the questions.

Master ‘X’ is a 3 year old child. He is living with his family in a slum. Public toilet is present near his house. His father is drunkard. His mother does not know the importance of balanced diet.

a. Master ‘X’ can suffer from which different possible diseases in above conditions?

Ans: Since, the house of master X is near the toilet and he lives in a slum area, the chances are that there is less cleaniliness in that area. There are chances that he may suffer from diseases like salmonellosis, shigellosis, diarrhoea, trachoma, gastroenteritis, giardiasis, tapeworm infection and threadworm infection.

 

b. How will you help him and his family in this situation?

Ans: In this case, the famliy needs to be made aware about cleanliness in and around their houses. There is a need to explain them the importance of balanced diet for them and their child. Since, the father is a drukyard, he needs counselling and treatment to get rid of the habit of alcoholism.

c. Which disease can occur to the father of master ‘X’?

Ans: The father of master X is a drunkyard which means he might suffer from diseases such as heart diseases, liver cirrhosis, ulcers and gastrointestinal ptoblems, brain damage etc.

 

6. Give the preventive measures of following diseases.

a. Dengue

Ans: Dengue is a mosquito borne disease which is transmitted by Aedes mosquitoes which grow in clean and stagnant water. The breeding of this mosquito can be prevented by adopting the following steps:

· larve-eating fishes should be introduced in ponds

· collection and storage of water should always be done in closed vessels

· potted plants should have proper drainage to avoid collection of water in the pots

· pesticides should be used against mosquitoes as and when required

 

b. Cancer

Ans: Preventive measures for cancer:

· have a healthy diet

· exercise regularly

· avoid smoking and alcohol

· go for regular health checkups

d. AIDS

Ans: Preventive measures for AIDS are:

· avoid sexual contact with unknown persons

· screening of blood before transfusion

· avoid sharing of needles

7. Explain the importance

a. Balanced diet

Ans: A balanced diet is a diet containing all nutrients (carbohydrates, fats, proteins, vitamins, etc.) in the right quantities. A balanced diet helps us in various ways:

· provides us with important nutrients required for the growth of body

· helps us to stay fit and free from diseases

· helps in strengthening the immune system

· helps our systems to function properly

· helps maintain a healthy weight

· reduces body fat

· provides the body with energy

· promotes good sleep and makes us feel better about ourselves

 

b. Physical exercise / Yogasanas

Ans: Importance of exercise and yogasanas are:

· reduces the risk of heart attack

· helps in managing weight better

· helps in maintaining blood cholesterol level

· lowers the risk of type 2 diabetes and some cancers

· helps in maintaining the blood pressure levels

· helps in attaining stronger bones, muscles and joints and lowers the risk of osteoporosis

· boosts the energy levels, makes you feel relaxed

 

8. Make a list.

a. Viral diseases

Ans:  Measels, Mumps, Swine flu, Chicken pox

 

b. Bacterial diseases.

Ans: Tuberculosis, Diptheria, Tetanus, Cholera, Typhoid

 

c. Diseases spread through insects.

Ans: Dengue, Malaria, Plague

 

d. Hereditary diseases.

Ans: Diabetes, Hypertension, Cancer

 

9. Write the information on modern diagnostics and treatments of cancer.

Ans: Diagnostics of cancer:

There are many techniques whiich are used in the diagnosis of cancer and their application depends upon the type of cancer. Biopsy, histopathological studies of bone and blood, radiography (use of X-rays), CT (computed tomography) and MRI (magnetic resonance imaging) are used in diagnosis of cancer. Radiography, CT and MRI are the modern techniques used in cancer diagnosis.
Computed tomography uses X-rays to generate a three-dimensional image of the internals of an object. MRI uses strong magnetic fields and non-ionising radiations to accurately detect pathological and physiological changes in the living tissue.

Treatment of cancer:

Cancer is treated using 3 major approaches depending on the type of cancer. These 3 approaches are- surgery, radiotherapy and chemotherapy. In surgery, the tumor is removed surgically from its site and can be used in specific cases only. Radiotherapy is a technique in which the cancer cells are irradiated with radiations taking care of the normal tissues which surround the cancer cells.
Chemotherapy uses different kinds of drugs for the treatment of cancer. These chemotherapeutic drugs are specific for particular tumors and have side effects such as hair loss, anemia, etc.
Most of the cancers are treated by the combination of these 3 approaches.

 

10. Enlist the names and composition of the medicines present at your home.

Ans: The following medicines are found in our houses:

Paracip- Paracetamol/Acetaminophen
Digene-  Dried Aluminium Hydroxide, Magnesium Aluminium Silicate Hydrate, Magnesium Hydroxide, Simethicone
Volini- Diclofenac diethylamine BP, Linseed Oil BP (Oleum Lini), Methyl salicylate, Menthol IP, Benzyl Alcohol IP.
Vomikind- Ondansetron