This MCQ module is based on: Chemical Properties of Metals and Non-metals
TOPIC 12 OF 46
Chemical Properties of Metals and Non-metals
🎓 Class 7
Science
CBSE
Theory
Ch 4 — The World of Metals and Non-metals
⏱ ~14 min
🌐 Language: [gtranslate]
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4.2 Chemical Properties of Metals and Non-metals
In Part 1 we looked at how metals and non-metals appear and feel. Now let us see how they react with other substances. Sudarshan uncle's iron tools slowly develop a reddish coat in the monsoon; burning a strip of magnesium in the lab gives a blinding flash of light. These are all chemical changes that reveal the chemical properties of each material.
4.2.1 Reaction with Oxygen (Burning & Tarnishing)
When a metal burns or is left in air, it combines with oxygen to form a metal oxide.
General reaction: Metal + O2 → Metal oxide
Activity 4.5 — Burning Magnesium Ribbon L3 Apply
Setup: With your teacher's help, hold a small magnesium ribbon with a pair of tongs and light one end over a flame. Do not look directly at the flame. Collect the white ash on a watch glass and dissolve it in a little water. Test the solution with red and blue litmus papers.
Predict: What colour flame will you see? How will the litmus paper change?
A dazzling white flame is seen; a white, powdery ash (magnesium oxide) collects on the watch glass. When dissolved in water, the solution turns red litmus blue — proving that the oxide is basic.
2 Mg + O2 → 2 MgO (white ash, basic)
Similarly, copper heated in air slowly develops a black coating of copper(II) oxide:
2 Cu + O2 → 2 CuO (black)
Iron reacts very slowly with oxygen in the presence of moisture to form reddish-brown rust:
4 Fe + 3 O2 + n H2O → 2 Fe2O3·n H2O (rust)
Non-metals with oxygen
Non-metals also burn in oxygen and form non-metal oxides, but these oxides are acidic — they turn blue litmus red.
S + O2 → SO2 (sulphur dioxide — acidic)
C + O2 → CO2 (carbon dioxide — acidic)
C + O2 → CO2 (carbon dioxide — acidic)
Nature of oxides
Metal oxide + water → base (turns red litmus blue).
Non-metal oxide + water → acid (turns blue litmus red).
Metal oxide + water → base (turns red litmus blue).
Non-metal oxide + water → acid (turns blue litmus red).
4.2.2 Reaction with Water
Not every metal reacts with water in the same way. Some go berserk, some need steam, and a few do nothing at all.
| Reactivity | Metals | Behaviour with water |
|---|---|---|
| Very reactive | Sodium (Na), Potassium (K) | React with cold water vigorously — sometimes so fast that the H2 gas released catches fire! |
| Moderately reactive | Magnesium, Calcium, Aluminium | React only with hot water or steam |
| Less reactive | Iron, Zinc | React only with steam (slow) |
| Least reactive | Copper, Silver, Gold | No reaction — even in boiling water |
2 Na + 2 H2O → 2 NaOH + H2 ↑
3 Fe + 4 H2O (steam) → Fe3O4 + 4 H2 ↑
3 Fe + 4 H2O (steam) → Fe3O4 + 4 H2 ↑
Non-metals, in general, do not react with water.
4.2.3 Reaction with Acids
Drop a clean strip of zinc into dilute hydrochloric acid (HCl). You will see tiny bubbles racing up the test tube — these are bubbles of hydrogen gas (H2). If you bring a burning matchstick to the mouth of the tube, you hear a sharp "pop". This is the famous pop test.
General reaction: Metal + Acid → Salt + Hydrogen gas ↑
Zn + 2 HCl → ZnCl2 + H2 ↑
Mg + H2SO4 → MgSO4 + H2 ↑
Zn + 2 HCl → ZnCl2 + H2 ↑
Mg + H2SO4 → MgSO4 + H2 ↑
Copper dropped into dilute HCl does not bubble at all — it is too unreactive. Non-metals do not react with dilute acids to release hydrogen, so the pop test is a neat way to spot a metal.
4.2.4 Reaction with Bases
Only a few metals, like aluminium and zinc, react with hot, strong bases (such as sodium hydroxide, NaOH) to release hydrogen gas. Most metals do not react with bases in everyday conditions.
Zn + 2 NaOH → Na2ZnO2 + H2 ↑
Reactivity Series (Simplified)
Scientists have arranged metals in order of how eagerly they react — the most reactive at the top, the least reactive at the bottom. This is the reactivity series.
K
Na
Ca
Mg
Al
Zn
Fe
Pb
Cu
Ag
Au
Most reactive → Least reactive
Memory trick: "Kind Naughty Cats Make Alligators Zoom In Peaceful Countries And Gardens" helps remember K, Na, Ca, Mg, Al, Zn, Fe, Pb, Cu, Ag, Au.
Acidic vs Basic Oxide — At a Glance
Interactive: Reactivity Quiz
Arrange these four metals from most to least reactive by dragging up/down, then press Check.
- Iron (Fe)
- Sodium (Na)
- Copper (Cu)
- Magnesium (Mg)
Competency-Based Questions L4 Analyse
In a lab, Ravi collects four test tubes A, B, C and D. Into each tube he pours dilute HCl. He then drops a clean strip of — A: magnesium, B: zinc, C: copper, D: aluminium. He brings a burning splint to the mouth of each tube after a minute.
1. In which tube will the 'pop' be loudest?
(a) A — Magnesium is the most reactive among the four; it releases H2 most vigorously.
2. In which tube will there be no reaction at all?
Tube C (copper). Copper lies below hydrogen in the reactivity series and does not react with dilute HCl.
3. Write the balanced equation of the reaction in tube B.
Zn + 2 HCl → ZnCl2 + H2 ↑
4. The white ash formed when Mg burns is dissolved in water and blue litmus is dipped in. What change will Ravi see? Explain.
Blue litmus remains blue because MgO + H2O → Mg(OH)2 is basic — bases do not change blue litmus. (Red litmus would turn blue.)
5. Fill in: Carbon dioxide and sulphur dioxide are ______ oxides because they turn ______ litmus ______.
acidic; blue; red.
Assertion–Reason Questions
(A) Both A & R true, R explains A • (B) Both true, R does not explain A • (C) A true, R false • (D) A false, R true.
A: Sodium is kept stored under kerosene oil.
R: Sodium reacts vigorously with moisture in the air and can catch fire.
(A) — Kerosene keeps sodium isolated from air and water, so R correctly explains A.
A: Copper vessels can safely hold dilute HCl without bubbling.
R: Copper is placed above hydrogen in the reactivity series.
(C) — Assertion is true, but R is false. Copper lies below hydrogen, which is why it does not displace H2.
A: CO2 turns blue litmus red.
R: CO2 is a non-metal oxide and is acidic in nature.
(A) — Non-metal oxides are acidic, and acids turn blue litmus red.
Frequently Asked Questions — Chemical Properties of Metals and Non-metals
What does the topic 'Chemical Properties of Metals and Non-metals' cover in Class 7 Science?
The topic 'Chemical Properties of Metals and Non-metals' is part of NCERT Class 7 Science Chapter 4 — The World of Metals and Non-metals. It covers the key ideas of chemical properties, metal oxides, non-metal oxides, reaction with acid, reaction with water, rusting, explained through everyday examples, labelled diagrams and hands-on activities drawn from the NCERT Curiosity textbook. Students learn not just definitions but also the reasoning behind each concept so they can answer competency-based questions and assertion–reason items. The lesson helps Class 7 students build a strong base for higher classes by linking each idea to real observations at home, school and in nature, and by preparing them for CBSE school assessments and Olympiads.
Why is 'Chemical Properties of Metals and Non-metals' important for Class 7 NCERT Science?
'Chemical Properties of Metals and Non-metals' is important because it builds core scientific thinking that Class 7 students will use throughout middle and secondary school. NCERT Chapter 4 — The World of Metals and Non-metals — introduces chemical properties and related ideas that appear again in Class 8, 9 and 10 Science. Mastering this subtopic helps students read labels and safety signs, understand news about science and technology, and perform better in CBSE school exams. The chapter also encourages curiosity and evidence-based thinking — skills that support the National Education Policy (NEP) 2020 focus on conceptual understanding and competency-based learning.
What are the key concepts students should remember from Chemical Properties of Metals and Non-metals?
The key concepts in 'Chemical Properties of Metals and Non-metals' for Class 7 Science are: chemical properties, metal oxides, non-metal oxides, reaction with acid, reaction with water, rusting. Students should be able to define each term in their own words, give at least one everyday example, and explain how the concept connects to other chapters in NCERT Class 7 Science. For example, linking the idea to daily life — in the kitchen, classroom or outdoors — makes revision easier. Writing short notes, drawing labelled diagrams and solving the NCERT in-text and exercise questions for Chapter 4 will help students retain these concepts for unit tests and the annual CBSE examination.
How is Chemical Properties of Metals and Non-metals taught using activities in NCERT Curiosity Class 7?
NCERT Curiosity Class 7 Science teaches 'Chemical Properties of Metals and Non-metals' using an inquiry-based approach with Predict–Observe–Explain activities. Students are asked to make a guess first, then perform a simple experiment with safe, easily available materials, and finally explain what they observed. This matches the NEP 2020 focus on learning by doing. For Chapter 4 — The World of Metals and Non-metals — the textbook includes hands-on tasks, labelled diagrams and questions that build Bloom's Taxonomy skills from Remember (L1) to Create (L6). Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding rather than rote memorisation.
What real-life examples of chemical properties can Class 7 students observe at home?
Class 7 students can observe chemical properties at home in many simple ways linked to 'Chemical Properties of Metals and Non-metals'. Kitchens, school bags, playgrounds and the night sky are full of examples that connect to NCERT Chapter 4 — The World of Metals and Non-metals. For instance, students can check labels on food and cleaning products, watch changes while cooking, or observe the Sun and Moon across a week. Keeping a small science diary — noting the date, what was observed and a quick sketch — turns everyday life into a science lab. These real-life connections make concepts stick and prepare students well for competency-based questions in CBSE Class 7 Science.
How does 'Chemical Properties of Metals and Non-metals' connect to other chapters of Class 7 Science?
'Chemical Properties of Metals and Non-metals' connects to many other chapters in NCERT Class 7 Science Curiosity. The ideas of chemical properties appear again when students study related topics like heat, light, changes, life processes and Earth-Sun-Moon. For example, understanding this subtopic helps in building mental models for later chapters and for Class 8, 9 and 10 Science. Teachers often use cross-chapter questions in CBSE examinations to test whether students can apply what they learned in Chapter 4 — The World of Metals and Non-metals — to new situations. This integrated approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.
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