Q1: What is rust?
Ans : When iron oxide is hydrated, it is known as Rust(Fe2O3. XH2O)
Q2: What is added to steel to make it stainless?
Ans: Stainless steel is made by mixing iron with carbon and metals like chromium, nickel and manganese.
Q3: What type of change is photosynthesis?
Ans : Chemical change
Q4: What is a chemical change?
Ans : A change, in which a new substance with different properties is formed, is known as a chemical change.
Q5: A change, in which a new substance with different properties is formed, is known as a _________________.
Ans : Chemical change
Q6: ___________is a property by virtue of which a metal can be beaten into thin sheets without breaking.
Ans : Malleability
Q7: Write the chemical formula of blue vitriol.
Ans : Crystals of copper sulphate pent hydrate (CuSO4.5H2O) are blue in colour. So, it is commonly known as blue vitriol.
Q8: State the two important conditions for rusting.
Ans : Presence of water and presence of oxygen
Q9: What is freezing point of water?
Ans : The freezing point is 0°C at which water freezes.
Q10: What is freezing of water?
Ans : Freezing is the process in which water turns to ice when cold enough (below 0°C temperature).
Q11: What is melting?
Ans : Melting is the process of turning a solid to a liquid.
Q12: Name the process by which water molecules continuously change to vapour.
Ans : Evaporation
Q13: At what temperature water evaporates?
Ans : 100 °C
Q14: Extraction of metal is a chemical process or physical process?
Ans : Chemical process
Q15: A medicine is the end product of the chain of ________________________.
Ans : Chemical reaction
Q16: Condensation of steam is chemical process or physical change?
Ans : physical change
Q17: Cutting of log of wood into pieces is a chemical process or physical change?
Ans : physical change
Q18: Name the two methods by which rusting of iron can be prevented.
Ans : By painting or greasing and by galvanizing with chromium or zinc
Q19: Give an example of chemical change in which heat, light, sound and unpleasant gases are produced.
Ans : Explosion of a firework
Q20: Define galvanisation.
Ans : The process of depositing a layer of zinc on iron is called galvanisation.
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