CBSE Class 7 Science Physical and Chemical Changes Worksheet with Solution by Expert Science Mam. Students of 7th Grade can solve this worksheet for extra preparation before exam. Private Teacher or Guardians of the Students can copy all the questions of this chapter and will match after solve their students.
Physical and Chemical Changes Class 7 Worksheet
Worksheet for Chapter No.6): – Physical and Chemical Changes
The following questions are important for your exams for 1 mark 2 mark or 5 marks. First solve the questions on your own and then saw the solution for understanding it better.
Practice worksheet for class 7
Section A
Q.1.) Define physical change ? Give one example?
→ A change in which substance undergoes a change in its physical properties is called as a physical change.
E.g., ice is converted into water.
Q.2.) What is chemical change ? Give one example?
→ A change in which a substance undergoes a change in its chemical properties called as chemical change. A change in which one or more new substances are formed called as chemical change.
E.g., rusting of iron.
Q.3.) What is chemical reaction give some examples?
→ Reaction in which one or more reactance reacts to produce one or more products is called as Chemical reaction.
Example:- digestion of food in our body, ripening of fruits, fermentation of grapes.
Q.4.) Who protects Earth from harmful radiation of the Sun? And how?
→ Ozone layer protects Earth from the harmful ultraviolet radiation which are coming from the Sun. Ozone absorb this radiation and breaks down to oxygen.
Q.5.) Who’s presence essential for rusting to happen?
→ The presence of both Oxygen and water is essential for rusting to happen.
Q.6.) Define crystallization? Give example?
→ Crystallization is the physical change in which large crystals of pure substances can be formed from their solution.
E.g., formation of salt by the evaporation of seawater.
Q.7.) What is galvanization ?
→ Galvanization is the process of depositing a layer of zinc on iron to prevent its corrosion or rusting of iron.
Q.8.) Classify the following changes as a physical or chemical changes?
→ 1.) Melting of ice – physical change
2.) Photosynthesis – chemical change
3.) Digestion of food :- chemical change
4.) Formation of Salt from seawater – physical change
5.) Rusting of iron – chemical change.
Q.9.) Write the two methods by which rusting of iron can be prevented ?
→ 1.) Galvanization
2.) By painting the piece of iron.
Q.10.) Why rusting of iron is faster at coastal regions than in the desert region?
→ 1.) At coastal regions, there is presence of a lot of moisture along with the oxygen around the region. Therefore, resting of iron is faster at coastal regions due to presence of moisture and oxygen.
2.) In case of desert region, there is presence of oxygen but lack of moisture and hence there is slower the rate of rusting of iron than in the coastal region.
Q.11.) Which gas is formed in the reaction of vinegar with baking soda ?
→ In the reaction of vinegar and baking soda , the carbon dioxide is get formed.
Q.12.) What will happen when carbon dioxide and lime water react together?
→ Carbon dioxide (CO2) + Lime Water [Ca(OH)2] → Calcium Carbonate
(CaCO3) + Water (H2O).
Q .13.) What happen when a cut apple is kept for open for a long period of time? Which kind of change it was ?
→ 1.) When we cut apple into pieces and kept it in the air exposed to oxygen and moisture for a long period of time it will turn brown in color due to the oxidation process .
2.) This is a type of chemical change.
Q.14.) Why brinjal and potatoes turn brown after cutting ?
→ 1.) Brinjal and potatoes contain polyphenol oxidase enzyme in it.
2.) When they are cut open and exposed to atmospheric Oxygen and moisture it will turn brown due to the oxidation process.
Q.15.) What happens when magnesium and oxygen react together ?
→ When magnesium and oxygen react together the magnesium oxide is get formed in the form of powdery Ash.
Magnesium (Mg) + Oxygen (O2) → Magnesium oxide (MgO)
Q.16.) What is the nature of the product of reaction between magnesium oxide and water ? Which litmus paper shows the nature of the product ?
→ Magnesium oxide (MgO) + Water (H2O) → Magnesium hydroxide
[Mg(OH)2]
In above reaction magnesium hydroxide is get formed. Magnesium hydroxide is a base hence red litmus paper turns blue in color.
Q.17.) Why there is a change in color from Blue to green between the reaction of copper sulphate and iron needle?
→ Copper sulphate solution ( blue) + Iron → Iron sulphate solution
(green) + Copper (brown deposit)
There is a change of colour from Blue to green due to formation of iron sulphate solution. When copper sulphate solution which is blue in colour reacts with iron it will form I am sulphate solution and copper is deposited on the iron needle and it becomes brown in colour.