In-text Questions — Corrosion and Alloys — Metals and Non-metals

1. 13 marksNCERT Cl-10 Science, In-text Qs after §3.5.1, Q1

   Metallic oxides of zinc, magnesium and copper were heated with the metals zinc, magnesium and copper (each oxide with each metal). In which cases will you find displacement reactions taking place?

   Hint. Use the reactivity order Mg > Zn > Cu, and remember a metal can't 'displace' itself from its own oxide.

   Step 1 — Recall the reactivity order for these three metals. Magnesium is more reactive than zinc, which is more reactive than copper: Mg > Zn > Cu.

   Step 2 — Work through the nine combinations. A displacement happens only when the added metal is more reactive than the metal already in the oxide. ZnO + Mg → displacement (Mg is more reactive than Zn). CuO + Zn → displacement (Zn more reactive than Cu). CuO + Mg → displacement (Mg more reactive than Cu). All other combinations — each oxide with its own metal, and MgO with either zinc or copper (both less reactive than Mg) — give no reaction.

   ✦ Answer: Displacement occurs in three cases: magnesium + zinc oxide, zinc + copper oxide, and magnesium + copper oxide, since in each of these the added metal is more reactive. No reaction occurs when a metal meets its own oxide, or when a less reactive metal is added to magnesium oxide.

   Where students slip. Expecting displacement whenever two different metals/oxides are combined — it only happens one way, when the metal added is more reactive than the metal in the oxide, not the reverse.

2. 21 markNCERT Cl-10 Science, In-text Qs after §3.5.1, Q2

   Which metals do not corrode easily?

   Hint. These are the same metals that stay shiny in jewellery for generations.

   Step 1 — Recall which metals resist corrosion. Metals that are low in reactivity don't react readily with air, moisture or acids, so they don't corrode easily.

   Step 2 — Name them. Gold, silver and platinum are all metals that resist corrosion, which is exactly why they are prized for jewellery.

   ✦ Answer: Gold, silver and platinum.

   Where students slip. Naming iron or copper — both of these corrode readily (rusting and greening respectively); the metals that resist corrosion are the unreactive ones near the bottom of the activity series.

3. 32 marksNCERT Cl-10 Science, In-text Qs after §3.5.1, Q3

   What are alloys?

   Hint. Think about stainless steel, brass, and bronze — what do all three have in common structurally?

   Step 1 — Define the term. An alloy is a homogeneous mixture of two or more metals, or of a metal and a non-metal.

   Step 2 — Explain how one is made and why. An alloy is prepared by melting the primary metal and dissolving other elements into it in fixed proportions, then cooling the mixture — this is done to give the resulting material improved properties, such as greater hardness or resistance to rusting, compared to the pure metal alone.

   ✦ Answer: An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal, made by melting the primary metal and dissolving the other elements into it in definite proportions — done to improve properties like hardness or corrosion resistance.

   Where students slip. Describing an alloy as just 'metals mixed together' without mentioning that it must be a homogeneous (uniform) mixture — a non-uniform blend of metals wouldn't have the same consistent improved properties.

Solutions written by the tuition.in editorial team and checked against the NCERT Class 10 Science textbook, Reprint 2026-27 (jesc103.pdf) — five in-text question sets (15 questions total, not 18 as some older manifests claim) plus one end-of-chapter Exercise (16 questions, correctly counted). Unchanged by rationalisation.. Questions are referenced from the NCERT textbook for identification.