Ncert- science – class 7- Chapter 5 – Physical and Chemical Changes 1

Welcome to your Ncert- science - class 7- Chapter 5 – Physical and Chemical Changes 1

A chemical change may involve-

Which of the following are chemical changes?

(i) Decaying of wood
(ii) Burning of wood
(iii) Sawing of wood
(iv) Hammering of a nail into a piece of wood

Choose the most appropriate answer:

     
Physical changes are:

Choose the most appropriate answer:  

  
Chemical changes involve;

Physical changes are:

Which of the following is not a chemical change?

Identify the chemical change in the following :

A student is given a mixture of barium sulfate, copper(II) sulfate and water. The table shows information about barium sulfate and copper(II) sulfate.

SubstanceSolubility in waterState at room temperature
Barium sulfateInsolubleSolid
Copper(II) sulfateSolubleSolid
How does the student obtain copper(II) sulfate crystals from the mixture?

Which of the following is a physical change

Two drops of dilute sulphuric acid were added to 

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1g of copper sulphate and then a small amount of hot water was added to dissolve it (step I). On cooling beautiful blue coloured crystals got separated (step II).Step(I) and step (II) are:

Paheli's mother made concentrated sugar syrup by dissolving sugar in hot water. On cooling, crystals of sugar got separated. This indicates:

Which of the following is a chemical change?

Baking of dough into bread is a kind of change

Identify the chemical changes in the list:

(i) Ripening of fruits
(ii) Fermentation of grapes
(iii) Magnetization of iron

Why is zinc better than tin if we want to protect a piece of iron from rusting by electroplating?

Which of the following statements is true?

Which of the following is a chemical change?

Magnesium hydroxide Mg(OH) 2 is used as:

Which of the following is the most common solvent used for crystallization?

All of the following processes involve a separation of either a mixture into its components or a compound into elements. For each, decide whether the physical process or chemical reaction is required.

a. Sodium metal is obtained from the substance Sodium chloride.
b. Iron filings are separated from the sand by using a magnet,
c. Sugar crystals are separated from sugar syrup by the evaporation of water.
d. Fine crystals of Silver chloride are separated from a suspension of the crystals in water.
e. Copper is produced when Zinc metal is placed in a solution of Copper (II) sulphate, a compound.

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