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What happens when a copper vessel is exposed to moist air for a long time ?

In which of the following cases, the centrifugation process is used for separation?

What were the demerits of Thomson's atomic model?

Do you see any change appearing when insoluble Calcium carbonate is formed in lime water?

Which metal is used for coating in galvanisation?

Koel was not able to understand that why water molecules are added with a dot at the end of most salts. Help her with this.

Which of the following is/are NOT solution(s)?

Non-biodegradable trash is a growing concern to
environmentalists these days. Explain ways by
which one can get rid of non-biodegradable wastes.
In your capacity what would you do to thrash this
waste

Coal is a

Which of the following is not a property of plastics?

What is the definition of non metals?

We use a pressure cooker to cook at high altitudes because of the following reason(s).

What will you observe if Hydrogen chloride gas is passed through blue litmus solution?

What would be the gravitational potential energy of an object whose mass is $\text{1kg}$ and is at a height of $\text{10m}$?$(takeg=9.8m{s}^{-}2)$

Q21. Consider the following statements

1. Spintronics exploits the quantum mechanical spin of electrons for micro- and Nano electronics.

2. Its applications range from videotape to MP3 players and hard disks.

Which of the above statements are correct?

Plastics are usually ___ .

State whether the following statements are true or false :

(a) All metals exist in solid form at room temperature.

(b) Coal can be drawn into wires.

(c) Non-metals react with dilute acids to produce hydrogen gas.

(d) Sodium is a very reactive metal.

(e) Copper displaces zinc from zinc sulphate solution.

(f) Rust formed on iron objects is basic in nature.

(g) Non-metals react with water to form a gas which burns with a 'pop' sound.

Match the entries of column I with column II:

Give reason for the following :

(a) Though lead is above hydrogen in the activity series, it does not react with dilute hydrochloric acid or dilute sulphuric acid.

(b) Potassium and sodium are not used fro reaction with dilute hydrochloric acid or dilute sulphuric acid in laboratory preparation of hydrogen.

What are the constituents of coal gas ? State one use of coal gas.

Which of the following statement is/are wrong in case of sodium chloride $NaCl$?

Which of the following metal have the highest melting and boiling point?

Is everything in the whole universe made up of atoms. If not what can be the examples given for such substance?

Identify the following as mixture or compound. [2 MARKS]

(i) blood
(ii) common salt
(iii) sugar
(iv) brass

Metals, except Al and Zn, react with oxygen to form _______ oxides.

Shiny took a paper cup of water and took a candle. He heated the paper cup using a candle, what do you think he will observe?

Assertion: Nitrogen and hydrogen combine together to form ammonia and heat.
Reason: It is an exothermic reaction.

Which option represents the correct characteristics of metals?

What are Petrochemicals? State its usage. [3 MARKS]

As a car runs out of petrol, what happens to petrol?

Which of the following is/are true?

Why is natural gas considered as a clean fuel

What are the advantages of using CNG and LPG as fuel ?

___ is used as a reducing agent in metal extraction.

The random movement of colloidal particles is called ___ motion.

Preeti describes a fabric as following:-

(a) It wrinkles easily.

(b) It absorbs water quickly.

(c) It is soft to touch.

(d) It is a plant fibre.

Which of the following fibres mentioned below can form such fabric?

Which of the following is/are the properties of hydrogen?

Explain the harmful effects associated with the disposal of plastics

The process of hot air rising over cold air is called

The decomposition of a compound by heat in the absence of air is called __.

Name two greenhouse gases? Which one of them produces the maximum greenhouse effect?

An oxidation reaction is one in which:

What do you observe when

(a) dilute sulphuric acid is added to granulated zinc ?

(b) a few pieces of iron are dropped in a blute solution of sodium chloride ?

(c) silver nitrate is added to a solution to a of sodium chloride ?

(d) ferrous sulphate solution is added to an aqueous solution of sodium hydroxide.

(e) solid lead nitrate is heated ?

(f) when dilute sulphuric acid is added to barium chloride solution ?

______________ obtained HCl in its purest form.