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प्रश्न
Write true or false :
When iron and sulphur are heated together a grey mass is formed which is attracted by a magnet .
पर्याय
True
False
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उत्तर
False
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संबंधित प्रश्न
How do the following help in bringing about a chemical change?
light.
Fill in the blank.
The formation of gas bubbles in a liquid during a reaction is called ......................
FILL IN THE BLANK
On reaction with sulphuric acid solution, barium chloride forms a white precipitate of ........ sulphate.
FILL IN THE BLANK
In a ............ change, new substances are formed.
TRUE \ FALSE
The evolution of a gas during a chemical reaction is shown by an arrow pointing downwards. True or false ?
Balance the following equation :
Fe + H2O → Fe3O4 + H2
Explain by writing a word equation.
Bubbles are seen on adding lemon juice to baking soda.
Define the following term:
Precipitate
State the original colour of the following substance and colour of residue obtained after heating.
Copper carbonate
Give a chemical test to distinguish between the following gases.
NH3 and SO2
Give a word equation for the following reaction.
An exothermic reaction where both the reactants are gases, one of which is oxygen.
Give reason for the following:
A characteristic change of colour is seen when a piece of iron is added to copper [II] sulphate solution.
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Addition of water to quicklime.
Give balanced equation for the following conversion affected by heat alone on the substance:
Copper carbonate to copper oxide
Complete the table given below.
| Heat on iodine crystals | Colour of vapours evolved |
Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.
Chemical change is a temporary change.
Write word equations for two chemical reactions with the help of materials given in the box.
| Air, copper sulphate, iron, vinegar, iron oxide, carbon dioxide, iron sulphate, copper, lime water, water |
______ are substances that speed up the process of a chemical change and it will not undergo any change during the course of the reaction.
The reaction of H2 gas with oxygen gas to form water is an example of ______.
