CBSE Class 8 - Science - Friction (MCQs) (#cbseNotes)

Friction (MCQs)

CBSE Class 8 - Science

Q1: The force of friction which opposes the surfaces just to slide one over the other, is called:

   (A) Limiting friction.
   (B) Rolling friction
   (C) Sliding friction
   (D) All of these.



Q2: What is the most common way to reduce friction?

(A) Lubrication.
(B) Warning signs.
(C) Eliminate the motion.
(D) None of these.



Q3: Do you want to increase or decrease friction when riding a bicycle?

(A) Increase.
(B) Both.
(C) Decrease.
(D) None of these.

CBSE Class 8 – Science – Microorganisms – Friends or Foes (Worksheet) (#cbseNotes)

Microorganisms – Friends or Foes (Worksheet)

Fill in the blanks 

1. Study of Microorganisms :  __________________


2. The size of bacterium is 3.5 microns =   ___________  mm       =         ___________ m


3. Microbes are divided into four categories:
i. _____________ ii. _____________
iii. _____________ iv. _____________


4. Viruses live on __________ line of living and non-living. They do not own _______ apparatus. They enter the body of living cell and start ___________.


5. The living cell inside which the virus grows and multiplies is known as ________.


6. Study of viruses is called ___________.

CBSE Class 8 - Science - Coal and Petroleum (Q and A) (#cbseNotes)

Coal and Petroleum

(NCERT Exemplar  Q & A)

Petroleum Refinery

Question 1: You are provided with a mixture of petroleum and water. Can you suggest a method to separate the two?

Answer: Decantation


Question 2: What does CNG stand for and why is it considered to be a better fuel then petrol?

Answer: CNG stands for compressed natural gas. It is considered to be a better fuel because it is less polluting.


Question 3: Name the petroleum product used as fuel for stoves, lamps and jet aircrafts.

Answer: Kerosene is used as fuel for stove,lamps and jet aircrafts.


Question 4: Fill in the blanks in the following sentences.

1. Coal is one of the ________ used to cook food.
2. When heated in air, coal burns and produces mainly _________ gas.
3. Coal Tar is a black, thick - with an ________ smell.
4. Petroleum, ______ and _______ are fossil fuels.
5. Forest and coal are _________ natural resources.

CBSE Class 8 - Science - CH4 Metals and Non-Metals (NCERT Exemplar Answers) (#cbseNotes)

Metals and Non-Metals 

NCERT Exemplar Answers

Multiple Choice Questions

Q1: Which of the following is not a metal?

(a) copper
(b) sulphur
(c) aluminium
(d) iron


Q2: The substance that will be flattened on beating with a hammer is

(a) crystal of iodine
(b) lump of sulphur
(c) piece of coal
(d) zinc granule

CBSE Class 8/10 - Metals vs Non-Metals (Comparison) (#cbseNotes)

Metals vs Non-Metals

Physical Properties Comparison

Property	Metals	Non Metals
Physical State	Most metals are solids at room temperature except mercury which is a liquid. Gallium and Cesium also changes into liquid at slightly above room temperature.	Non Metals exist in all states. Eleven are gases, bromine is liquid while others are solids.
Melting and Boiling Point	Generally have high melting and boiling points. (Exceptions are Gallium, Mercury, Sodium and Potassium.)	Generally they have low melting and boiling points. Exceptions are: Carbon, Boron and Silicon.
Density	They have high density except Sodium and potassium.	Low denisty (Diamond is an exception.)
Lusture	Metals shine and are lustrous.	Non-metalls appear dull. (Exceptions are Diamond, graphite and iodine.)

CBSE Class 8 - Science - CH 13 - Sound (Question Bank) (#cbseNotes)

SOUND

Question Bank

Very Short Answer Type Questions

Q1: Define vibration.

Q2: What is meant by oscillatory motion?

Q3: How is sound produced?

Q4: Can sound travel in vacuum?

Q5: Define amplitude.

CBSE Class 8 - Science - CH4 Metals and Non-Metals (Assignment) (#cbsenotes)

CBSE Class 8 - Science - CH4 Metals and Non-Metals (Assignment)

CBSE Class 8 - Biology - Cell Organelles, Location and Functions (#cbsenotes)

Cell Organelles, Location and Functions

Organelles	Present In	Description	Function
Cell Wall	Plants only	Outer most covering, stiff shape, made of cellulose	Protects the cell from temperature variation, inside water pressure and moisture, procvides structural strength
Cell Membrane	Both plants and animals	Plants inside the cell wall. Animal: thin outermost selectively permeable	Allows exchange of selected substance, supports the cell, separates the cell from its environment.
Nucleus	Both plants and animals	Oval shaped body	Control cell activities, transmits genetics characteristics
Cytoplasm	Both plants and animals	Thick jelly like fluid containing other cell organelles	Site of all life (metabolic) processes, protects cell organelles
Mitochondria	Both plants and animals	Rod shaped body	Site of respiration, releases energy form sugar, called power house of the cell
Golgi body	Both plants and animals	Parallel stacked vesicles	packaging and dispatch of proteins and lipids, helps in lysosomes formation
Endoplasmic reticulum	Both plants and animals	Networks of tubes and membrane	Transportation of materials.
Ribosomes	Both plants and animals	Small bodies, sometimes attached to endoplasmic reticulum	protein synthesis
Vacuole	Plant: single and large. Animal: very small or absent	Sac-like structure in cytoplasm	Stores food and water (cell sap)
Plastids	Only Plants	Small colored bodies in cytoplasm	Impart color to leaf, flower and fruit
Lysosomes	Generally animals	Membrane bound sac in cytoplasm filled with digestive enzymes	Eats up(digests) damaged cells and unwanted cell products

✎Note: See ☛ Class 8 Science - Cell (NCERT Q and A)
☛ Cell - MCQs
☛Cell Structure and Functions (Q and A)

CBSE Class 8 - SA2 Science Sample Question Paper Set-2 (2016-17)(#cbsepapers)

CBSE Class 8 - SA2 Science Sample Question Paper (2016-17)

CBSE Class 8 - Science -SA2 Sample Question Paper (2016-17)

CBSE Class 8 - Science SA2 Sample Question Paper (2016-17)

CBSE Class 8 - Science - REACHING THE AGE OF ADOLESCENCE

REACHING THE AGE OF ADOLESCENCE

Q & A Based NCERT Class 8 Science Chapter


Q 1: List the changes occur during adolescent age.

Answer:
CHANGES OCCUR AT ADOLESCENT AGE:
1) INCREASE IN HEIGHT
2) DEVELOPMENT OF HAIR
3) SEXUAL FEELING
4) VOICE CHANGES
5) CHANGE IN BODY SHAPE
6) CHANGE IN BEHAVIOUR AND ATTITUDES
7) ACTIVITY OF SWEAT AND OIL GLANDS


Q 2: What is the function of endocrine system? What is it made up of?

Answer: There are a number of other slower processes that go on in the body, such as growth such processes are primarily controlled by the endocrine system.

The endocrine system consist of a number of ductless glands that secrete hormones.


Q3: What is Adam's apple?

Answer: Adam's apple: The protruding part of the throat is called Adam’s apple. It is the enlarged voice box or larynx which gets enlarged and visible from outside in boys at the onset of puberty. This makes the voice of boys hoarse.


Q 4: Name four body processes that hormones control?

Answer: Growth behavior, development and reproduction are controlled by hormones.

Class 8, 10: Science - Uses of Some Common Metals and Non-Metals

Uses of Some Common Metals and Non-Metals

USES OF SOME COMMON METALS

Metal	Main Uses
Iron	Bridges, Train tracks, Construction Bars, Steel, Engine Parts, Iron sheets etc.
Copper	Electrical Wires, Utensils, Coins etc.
Aluminium	Electric Wires, Utensils, Airplanes, Metallic Paints, Foil for packaging etc.
Silver	Jewellery, Electroplating, photography, Utensils, Coins, silvering of mirrors etc.
Gold	Jewellery and Decorations, Coins
Lead	Batteries, Alloys, Paints, Alloys like solder, Protective screen for X-Rays etc.
Mercury	Thermometers, Barometers, Dental amalgams etc.

CBSE Class 8 - Science - COMBUSTION AND FLAME (HOTS Questions and Answers)

COMBUSTION AND FLAME

Forest Fires - Why do forests catch fire in hot summers?

HOTS Q & A (Class 8 Living Science Textbook Chapter Solutions)

Q1: Only gases burn with a flame. When you burn wood it initially burns with a flame. Later it only glows without a flame. What do you think the answer is?

Answer: Wood contains many chemicals like resin, lignin. When heated, these chemicals broke up and release combustible gases. That's why wood burns initially with a flame. When these gases are exhausted, wood burns without flame.


Q2: Would you consider coal as a good fuel? Give reasons?

Answer: Coal is not considered as a good fuel because of the following reasons:

1. It has low calorific value as compared to Petroleum and LPG.

2. On burning it releases many polluting gases like CO2 which is a green house gas and it causes global warming.

3. Coal contains traces of Sulphur and Nitrogen which on burning gives harmful gases like Nitrogen Oxide and Sulphur Oxide. These gases when mixed with rain water cause acid rain.

4. Unburnt traces of carbon also causes respiratory problems.


Q3: When a fuel is burnt, carbon dioxide (or carbon monoxide) and water vapour are given out. Can you name one fuel which burns without giving off water vapour? Why does it not give out water?

Answer: Charcoal is pure form of carbon. When it burns with oxygen, it forms carbon dioxide and no waters vapours are given off.


Q4: Why does a matchstick burn on rubbing it on the side of the match box?

Answer: Matchstick uses chemicals like phosphorus which has low ignition temperature (35°C). When the stick is rubbed, due to friction heat is generated which is sufficient to raise temperature to above 35°C and ignites the stick.

CBSE Class 8 - Science - MICROORGANISMS AND VIRUSES – Friends and Foes! (Q and A)

MICROORGANISMS   AND VIRUSES – Friends and Foes!

(Chapter Solutions of textbook Prachi Science for Class 8)

Fungal Infected Bread

Q1.  Answer in one word.

1. Name two typical habitats of micro-organisms

Answer: Commonly found everywhere – in the air, in water, inside the bodies of living organisms.

2. Name a disease caused by bacteria

Answer: Tuberculosis, Pneumonia

3. Name the microorganism that is used for obtaining alcohol from sugar.

Answer: Yeast.

4. Name one carrier of disease-causing microorganisms.

Answer: House Fly which causes many diseases like cholera, typhoid, diarrhoea.

5. Where do the external parasites of animals live?

Answer: External parasites like lice, flies, ticks, grubs etc. live on the skins of the animals.

Q2. Short- Answer Questions (10-15 words)

CBSE Class 8 - Science - METALS and NON Metals : Question and Answers

METALS and NON Metals : 

Question and Answers

Prachi Class 8 Science Textbook Solutions

Activity Series

Q1: Identify the type of elements which are neither malleable nor ductile.

Answer: Non-metals (eg Carbon, Phosphorous, Sulphur, Nitrogen) are neither malleable nor ductile.


Q2: Name a property which is common to the metals occurring near the bottom of the reactivity series.

Answer: These (Silver, Gold and Platinum) are least reactive metals and are found in free state in the earth's crust.


Q3: Name a metal that is kept under kerosene.

Answer: Sodium.


Q4: What type of reaction is the reaction between copper sulphate solution and zinc plate?

Answer: It is a displacement reaction.
        Zn + Copper Sulphate ---------> Zinc Sulphate + Copper

(Explanation: Zinc is more reactive than copper, Therefore Zn displaces Cu.)



Q5: An oxide of sulphur turns blue litmus red. Is it acidic or basic?

Answer: Acidic

CBSE Class 8 - Living Science (CCE Edition) : Crop Production (Text Book Answers)

Living Science (CCE Edition) : Crop Production 

Textbook Answers

Multiple Choice Questions (pg 20)

Q: Which of these is not a cereal?...

Answers:

1: (a) Gram
Explanation: Gram is a legume (pulses) while others are cereals

2: (a) Wheat
Explanation: Wheat is a rabi (winter) crop.

3: (a) organic nutrients
Explanation: Compost is made of dead and decaying organic matter.

4: (a) Wilt
Explanation: Wilt is caused by bacteria while others are fungal infections.

5: (c) it prevents soil erosion.
Explanation: Ploughing loosens soil so that more air can fill up the spaces.

6: (d) All of these

7: (d) ploughing
Explanation: Manuring or Fertilizers or Field Fallowing add nutrients.

8: (b) Combine

VERY SHORT ANSWER QUESTIONS (One word answers) - Pg 20-21

Q1. About how many years ago did agriculture begin?...

CBSE Class 8 - Science - Chapter 1 - Crop Production and Management (Questions and Answers)

Crop Production and Management 

Types of Crops (based on Seasons)

Questions and Answers based on Class 8 NCERT Chapter

Q1: Define agriculture.

Answer: It is a science that deals with the growth of plants and animals for human use is called agriculture.

Q2: Define Crop

Answer: When plants of the same kind are grown and cultivated at one place on a large scale, it is known as a crop. For example, crop of wheat means that all the plants grown in a field are that of wheat.

Q3: What are agricultural practices?

Answer: All the activities which are involved in the cultivation of crops from sowing to harvesting are known as agricultural practices.

Q4: Why does India need improved agricultural practices?

Answer: Following are the reasons that India need improved agricultural practices:

i. India's population is around 1.20 Billion and it is growing faster than its ability to produce wheat and rice.
ii. To provide sufficient food to such a large population, it is required to maintain regular production and proper crop management.
iii. It requires an improvement in agricultural practices and application of latest technology.


Q5: List the seven agricultural practices.

Answer:
i.   Preparation of soil
ii.  Sowing
iii. Adding manure and fertilisers
iv.  Irrigation
v.   Protecting from weeds
vi.  Harvesting
vii. Storage

CBSE Class 8 - Science - Chapter 8 - Cell Structure and Functions (Q and A)

Cell Structure and Functions

Questions and Answers based on NCERT Chapter

Q1: Define Cell 

Answer: Cell is the basic structural and functional unit of life.


Q2: Who was the first person to see the cell?

Answer: Robert Hooke, who was the first person to see the cell, in 1665 observed slices of cork under a simple magnifying device.


Q3: What is cork made up of?

Answer: It is a part of the bark of a tree and is made of dead cells.


Q4: Can we see cells with unaided eye?

Answer: Usually animal and plant cells are so small that these can't be seen by the unaided eye. We need a microscope to observe cells. There are few exceptions like hen's egg cell or ostrich's egg which is made up of one large cell that can be seen by an unaided eye.


Q5: Name the largest cell.

Answer: Ostrich's egg.


Q6: What does "cellula" mean in Latin?

Answer: It means a small chamber.


Q7: Name the scientist who discovered nucleus of the cell?

Answer: Robert Brown

CBSE Class 8 - Science Ch 13 - Sound (Worksheet)

Sound

Worksheet

Prolonged Use of Headphones and loud music can make you deaf

Write True or False for the senses given below. Also rewrite the false statements correctly:



1. Sound is a mechanical wave.

______________________________________________________


2. Sound can travel through vacuum.

_______________________________________________________



3. Sound is produced by a vibrating body.

_______________________________________________________



4. The maximum displacement of a body from its mean position is called amplitude of oscillation.

________________________________________________________


5. Loudness of a sound is measured in Hertz.

_______________________________________________________

CBSE Class 8 - Science - CH 15 - Some Natural Phenomena (Worksheet)

Some Natural Phenomena

Tsunami hits at San Jose: picture by Angela Riddock

Worksheet based on Class 8 NCERT Chapter 15

Fill in the blanks with appropriate words given below:

seismograph, Ritcher scale, static, earthquake, positive, earthing, thunder, Like charges, seismic waves, unlike charges, electroscope

1. _______ electricity consists of electric charges which do not flow.


2. A glass rod when rubbed with a piece of silk cloth gets charged with ________ charge.


3. Seismic waves are recorded by an instrument called ____________.


4. An explosive sound heard during lightning is termed as _________.


5. _____ _______ repel each other while ______ _______ attract each other.