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 9 - Chemistry - CH2 - Is Matter Around Us Pure? (Short Q and A)

Is Matter Around us pure?

Short Q & A

Simple Distillation Technique.
Can you name the labelled parts? See answer at wikimedia

Q1: Who was the first scientist to use the term 'element'?

Answer: Robert Boyle was the first scientist to use the term element in 1661.


Q2: Name the chemist who for the first time, defined an element as a basic form of matter that cannot be broken down into simpler substances by chemical reactions.

Answer: Antoine Laurent Lavoisier (1743-94), a French chemist


Q3: Who is known as the father of Modern Chemistry?

Answer: Antoine Laurent Lavoisier (1743-94), a French chemist


Q4: Do physical changes alter the identity of a substance?

Answer: No.

Class 8 - Maths - Algebraic Expressions and Identities (NCERT Ex 9.2 Answers)

Algebraic Expressions and Identities 

(NCERT Ex 9.2 Answers)

Q1: Find the product of following pair of monomials.

(i) 4 , 7p

Answer:

4   ☓   7p = 4  ☓ 7   ☓ p = 28p

(ii) -4p , 7p

Answer:

-4p   ☓   7p = -4 ☓ p ☓ 7  ☓ p = (-4☓7)☓ (p☓ p) = -28p²

(iii) 4p , 7pq

Answer:

-4p  &#9747 7p = -4 ☓ p ☓7  ☓ p  ☓ q = (-4☓ 7)☓ (p☓ p☓ q) = -28p²q

(iv) 4p³ , -3p

Answer:

4p³  ☓  -3p = 4  ☓(-3)   ☓ p ☓ p☓ p☓ p = -12p⁴

(v) 4p , 0

Answer:

4p ☓ 0 = 4☓ p☓ 0 = 0


Q2: Find the areas of rectangles with the following pairs of monomials as their lengths
and breadths respectively.

(p , q);(10m , 5n);(20x² , 5y²);(4x , 3x²);(3mn ,4np)

Answer:

We know that,

Area of rectangle = Length ☓ Breadth

Area of 1^st rectangle = p ☓ q = pq

Area of 2^nd rectangle = 10m ☓ 5n = 10☓ 5 ☓ m ☓ n = 50mn

Area of 3^rd rectangle = 20x² ☓ 5y² = 20☓ 5 ☓ x² ☓ y² = 100x²y²

Area of 4^th rectangle = 4x ☓ 3x² = 4☓3 ☓ x ☓ x² = 12x³

Area of 5^th rectangle = 3mn ☓4np = 3☓ 4 ☓ m ☓ n ☓ n ☓ p = 12mn²p


Q3: Complete the table of products.

First Monomial (⇨) Second Monomial(⇩)

2x

-5y

3x2

-4xy

7x2y

-9x2y2

2x	4x2	...	...	...	...	...
-5y	...	...	-15x2y	...	...	...
3x2	...	...	...	...	...	...
-4xy	...	...	...	...	...	...
7x2y	...	...	...	...	...	...
-9x2y2	...	...	...	...	...	...

Answer:

CBSE Class 10 - Science - CH7: Control and Coordination (VSQA)

CONTROL AND COORDINATION

Very Short Question And Answers

Q1: Which chemical induces artificial ripening of fruits?

Answer: Ethylene


Q2: What is stimulus?

Answer: The changes in the environment to which an organism responds and reacts is called stimulus.


Q3: Name the longest cell present in the human body.

Answer: Neuron is the longest cell in the human body.


Q4: Give examples of glands which act as both endocrine and exocrine.

Answer: Pancreas, Testes, Ovaries


Q5: What are nastic movements?

Answer: Movements of plants which are independent of stimuli are called nastic movements. e.g. movement by Touch-Me-Not (Mimosa) plant i.e. leaves close or droop when touched.


Q6: Where do you find gustatory receptors?

Answer: On the tongue.


Q7: What do olfactory receptors detect?

Answer: They detect smell.


Q8: Name the hormone released by thyroid gland.

Answer: Thyroxin.


Q9: Where is Hypothalmus is located?

Answer: In the brain.

Class (6 - 12) English Grammar - KINDS OF SENTENCES (Part 1)(#eduvictors)(#englishgrammar)

KINDS OF SENTENCES (Part 1)

Sentences based on functions are categorised as follows:

1. Assertive Sentences
2. Interrogative Sentences
3. Imperative Sentences
4. Optative Sentences
5. Exclamatory Sentences

Assertive Sentences

These sentences merely assert an incident or a fact.
e.g.
The sun is a big star. (Affirmative)
The Taj is a beautiful monument.         (Affirmative)
He is not in Delhi. (Negative)
It does not glow at night.         (Negative)

Sentences that affirm one or the other fact are called affirmative sentences. First two sentences listed above are affirmative ones.

Sentences that negate a fact are called negative sentences. The last two sentences listed above are negative sentences.

Exercise:
Convert the following affirmative sentences into negative sentences by giving negative meaning also.

1. I like him.
2. Banana is a sweet fruit.
3. They play for Delhi Soccer club.
4. We sing a song.
5. He gets up early.


Answers:
1. I do not like him.
2. Banana is not a sweet fruit.
3. They do not play for Delhi Soccer club.
4. We do not sing a song.
5. He does not get up early.

CBSE Class 9 -12: English Grammar Quiz

ENGLISH GRAMMAR QUIZ

[Questions from SSC Exam Paper 2014]
Q (1 - 5) In these questions some part of the sentences have errors and some are correct.Find out which part of the sentence has error and mark that part (A), (B) or (C). If a sentence is free from error, then mark (D) as your answer.


Q1: In his book (A)/ Churchill describes (B)/ that historical first meeting with Roosevelt (C)/ No error (D).

Q2: The ant who was nearby (A) / walked forward and bit the hunter (B)/ sharply in the ankle (C) / No error (D).


Q3: They can promise you (A) / an experience (B) / you won't never forget (C)/ No error (D)


Q4: The dress that the (A) / girl wore was (B)/ more attractive than the other girls (C)/ No error (D)


Q5: Fifty years has passed (A)/ since man first ventured (B)/ in outer space (C)/ No error (D).


Directions (6 - 10): Fill up the blanks with approproate word(s) in the sentences. Four options are given, choose the correct one. 


Q6: I can ______ him without qualifications.

(a) recommend
(b) commend
(c) praise
(d) suggest


Q7: She let her horse ________ in the field.

(a) loosen
(b) loose
(c) loosely
(d) lose