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VII science Hots Questions

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Q. Is shampoo acidic or basic? 

Shampoo is generally made by the salts of a weak acid and a strong base, so they're somewhat basic. Shampoos usually are at pH 5.5 because at slightly acidic pH the scales on a hair follicle lay flat making the hair feel smooth and look shiny. Citric acid is used to adjust the pH down to 5.5 (is). It is a fairly weak acid which makes the adjustment easier.

Q. Why government has put ban on the sale of shahtoosh shawls?

Shahtoosh shawl, made from the wool of endangered Tibetan antelope, Chiru which is a rare animal Therefore, government has put ban on the sale of shahtoosh shawls for the purpose of conservation and protection

 Q. Why is sericulture not considered on eco-friendly practise?

 Sericulture not considered on eco-friendly practice because during sericulture silk worm is boiled to get silk fibres. Vapours emitted from the boiling cocoon release toxic fumes that pollute the atmosphere contribute to respiratory problem.

Q. Why is shearing usually done in summer?

Shearing is usually done in summer because ships do not require insulating material in summer.

Q. Is burning of candle physical or chemical change or both?

Burning of candle is both. When candle burn wax melts that is a physical change but some wax burn and produce gas this is a chemical change.

Phenomena during the candle burning: 
- melting (physical phenomenon)
- evaporation (may be considered a chemical but also a physical phenomenon)
- oxidation - reaction with oxygen, burning (chemical phenomenon)
- thermal decomposition (chemical phenomenon)

Q. The atomicity of oxygen in ozone is 1.5 times that of oxygen in oxygen molecule derive the formula of ozone. 

Atomicity of oxygen in oxygen molecules = 2

Atomicity of oxygen in ozone molecules = 1.5 x 2=3

Hence the formula of ozone = O3

Q. Why iron gates are painted? 

Iron gates are painted to protect from moisture and air and hence prevent.

Q. Why are toothpastes basic in nature?

 In our mouth bacteria produce acid which dissolves enamels therefore prevent acid formation we use toothpastes. The main job of a toothbrush & toothpaste is to remove Plaque , a thin film formed by bacteria on teeth & gums.

Q. Decide which is more acidic or more basic

Strong acid + strong Base ----> neutral salt pH= 7

Weak acid + strong Base ---> Basic salt pH>7

Strong acid + strong Base --> Acidic salt pH< 7

Q. Why does thick glass tumbler crack when you pour hot tea into it?

When you pour hot tea into thick glass tumbler , inner surface expand more than outer surface as glass is bad conductor of heat. Hence unequal expansion crack glass tumbler.
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CBSE ADDA :By Jsunil Sir : Your Ultimate Destination for CBSE Exam Preparation and Academic Insights

Class 10 Chapter 02 Acid Bases and Salts NCERT Activity Explanation

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NCERT Activity Chapter 02 Acid Bases and Salt Class 10 Chemistry Activity 2.1 Indicator Acid Base Red litmus No Change Blue Blue Litmus Red No change Phenolphthalein Colourless Pink Methyl Orange Pink   Yellow Indictors are substance which change colour in acidic or basic media. Activity 2.2 There are some substances whose odour changes in in acidic or basic media. These are called olfactory indicators. Like onion vanilla, onion and clove. These changes smell in basic solution. Activity 2.3 Take about 5 mL of dilute sulphuric acid in a test tube and add few pieces of zinc granules to it. => You will observe bubbles of hydrogen gas on the surface of zinc granules. Zn + H2SO4 --> ZnSO4 + H2 => Pass the Hydrogen gas through the soap solution. Bubbles formed in the soap solution as Hydrogen gas it does not get dissolved in it
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CBSE I NCERT 10th Numerical Problem solved Reflection and reflection of light

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Q. 1. A concave mirror of focal length 20cm is placed 50 cm from a wall. How far from the wall an object be placed to form its real image on the wall?  Solution: V= -50 cm F= -20cm From mirror formula 1/u = 1/f – 1/v = -1/20+ 1/50 = - 3/100  U = - 33.3 cm Therefore, the distance of the object from the wall x =  50 – u X = 50 – 33.3 = 16.7 cm. Q.2. An object is placed at a distance of 40cm from a concave mirror of focal length 15cm. If the object is displaced through a distance of 20 cm towards the mirror, By how much distance is the image displaced? Answer: Here f = - 15 cm, u = - 40 cm Now 1/f = 1/u + 1/v Then 1/v = 1/f – 1/u Or V= uf/u-f =( - 40 x -15)/25 = -24 cm Then object is displaced towards the mirror let u1 be the distance object from the Mirror in its new position. Then u1 = -(40-20) = -20cm If the image is formed at a distance u1 from the mirror then v1 = u1f/u1-f = -20X-15/-20+15 = -60 cm. = - 20 x-15/-20+15 = -60 cm. Therefor
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Class 10 Metal and Non MetalsChapter 03 NCERT Activity Solutions

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X Class 10 NCERT Activity Explanation Class 10 Metals and Non Metals Activity 3.1 Page No. 37 Take samples of iron, copper, aluminium and magnesium. Note the appearance of each sample. They have a shining surface. Clean the surface of each sample by rubbing them with sand paper and note their appearance again. They become more shiny. => Freshly cut Metal have shiny surface Activity 3.2 Page No. 37 Take small pieces of iron, copper, aluminium, and magnesium. Try to cut these metals with a sharp knife and note your observations. They are very hard to cut. Hold a piece of sodium metal with a pair of tongs and try to cut it with a knife. Sodium can be cut easily with knife. Hence K and Na are soft metal cut with knife Activity 3.3 Page No. 38 Take pieces of iron, zinc, lead and copper try to strike it four or five times with a hammer. These metals are beaten into thin sheet on hammering. This property of metal is called malleability and metals are called malleable. Activity 3.4 Page
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Living science ratna sagar class 6 solutions

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Ratna sagar living science 6 answers by jsunil. Class6 Living science solution Term-1 Living Science Solution chapter-1 Source of food Download File Living Science Solution chapter-2 Component of food Download File Living Science Solution chapter-3 Fibre to fabric Download File Living Science Sol ch-4 Sorting of material into group Download File Living Science Soln ch-5 Separation of substance Download File Living Science Solution chapter-6 Change around Us Download File Living Science Solution ch-7 Living and Non Living Download File Living Science Solution ch-8 Getting to Know Plants Download File Living Science Sol ch-9 The Body and Its movements Download File Visit given link for full answer Class6 Living science solution Term-II
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Electricity numerical for class 10 CBSE Trend Setter 50 Problems

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1. The current passing through a room heater has been halved. What will happen to the heat produced by it? 2. An electric iron of resistance 20 ohm draws a current of 5 amperes. Calculate the heat produced in 30 seconds. 3. An electric heater of resistance 8 ohm takes a current of 15 A from the mains supply line. Calculate the rate at which heat is developed in the heater. 4. A resistance of 40 ohms and one of 60 ohms are arranged in series across 220 volt supply. Find the heat in joules produced by this combination in half a minute. 5. A resistance of 25 ohm is connected to a 12 V battery. Calculate the heat energy in joules generated per minute. 6. 100 joules of heat is produced per second in a 4 ohm resistor. What is the potential difference across the resistor? 7. An electric iron is connected to the mains power supply of 220 V. When the electric iron is adjusted at minimum heating’ it consumes a power of 360 W but at ‘maximum heating’ it takes a power of 840 W. Ca
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