Science · Class 8 · Sustainable Food Production · Term 1

Chemical Properties of Metals and Non-metals

Investigating the reactivity of metals and non-metals with oxygen, water, acids, and bases.

• CBSE Learning Outcomes
• CBSE: Materials: Metals and Non-Metals - Class 8

About This Topic

Chemical properties of metals and non-metals highlight their distinct reactivity with oxygen, water, acids, and bases, as per CBSE Class 8 standards on materials. Metals follow a reactivity series, where highly reactive ones like magnesium burn in oxygen to form basic oxides, react with cold water to evolve hydrogen, and displace less reactive metals from salts. Non-metals, such as sulphur, form acidic oxides and show little reaction with dilute acids or water.

Students compare products like metal salts and hydrogen from acid reactions, or predict outcomes in displacement reactions, such as zinc displacing copper from copper sulphate solution. This builds foundational knowledge for periodic table trends and explains real-world applications, from rust prevention on Indian railway tracks to uses of inert metals like gold in jewellery.

Practical investigations reinforce these concepts through observation of colour changes, gas evolution, and litmus tests. Active learning benefits this topic because students conduct safe microscale experiments, predict results based on the reactivity series, and discuss discrepancies, which strengthens prediction skills and laboratory confidence.

Key Questions

1. Explain the difference in reactivity of metals and non-metals with oxygen.
2. Compare the products formed when metals and non-metals react with acids.
3. Predict the outcome of a displacement reaction between a more reactive and less reactive metal.

Learning Objectives

• Compare the products formed when common metals (e.g., magnesium, iron) and non-metals (e.g., sulphur, carbon) react with oxygen, identifying whether the resulting oxides are acidic or basic.
• Explain the reactions of reactive metals (e.g., sodium, potassium) with water, classifying the products and the energy released.
• Analyze the displacement reactions between metals using a reactivity series, predicting which metal will displace another from its salt solution.
• Classify oxides of metals and non-metals as acidic or basic based on their reaction with water or litmus paper.
• Demonstrate the difference in reactivity of metals and non-metals with dilute acids through microscale experiments, identifying gas evolution or lack thereof.

Before You Start

Atoms, Molecules, and Elements

Why: Students need to understand the basic building blocks of matter and the concept of different elements to grasp how they react.

Physical and Chemical Changes

Why: Understanding the difference between physical and chemical changes is crucial for identifying and describing chemical reactions involving metals and non-metals.

Acids, Bases, and Salts

Why: Prior knowledge of the properties of acids and bases, including their reactions with indicators like litmus, is necessary for understanding the nature of metal and non-metal oxides.

Key Vocabulary

Reactivity Series	An ordered list of elements that shows their reactivity relative to each other. More reactive elements can displace less reactive elements from their compounds.
Oxidation	A chemical reaction involving the loss of electrons or an increase in oxidation state. In this context, it often involves reaction with oxygen.
Acidic Oxide	An oxide that reacts with water to form an acid, or reacts with a base to form a salt and water. Typically formed by non-metals.
Basic Oxide	An oxide that reacts with water to form a base, or reacts with an acid to form a salt and water. Typically formed by metals.
Displacement Reaction	A reaction in which a more reactive element displaces a less reactive element from its compound. For example, a more reactive metal displacing a less reactive metal from its salt solution.

Watch Out for These Misconceptions

Common Misconception

All metals react equally with dilute acids.

What to Teach Instead

Metals vary by reactivity series; copper shows no reaction while magnesium evolves hydrogen vigorously. Station rotations let students compare directly and construct the series, correcting overgeneralisations through evidence.

Common Misconception

Non-metals react with acids like metals do.

What to Teach Instead

Non-metals like sulphur do not produce hydrogen with dilute acids. Paired tests with litmus reveal no change, prompting discussions where students refine models via peer explanations.

Common Misconception

Metal oxides are acidic.

What to Teach Instead

Metal oxides turn red litmus blue, showing basic nature. Hands-on litmus tests in small groups build correct associations, as students test and share results to challenge initial ideas.

Active Learning Ideas

Stations Rotation: Metal Reactivity with Acids

Prepare stations with magnesium, zinc, iron, and copper strips in dilute HCl test tubes. Students observe fizzing, test gas with a burning splint, and note reactivity order. Groups rotate every 10 minutes and compile a class reactivity series chart.

40 min·Small Groups

Displacement Reaction Pairs: Zinc and Copper Sulphate

Pairs add zinc granules to blue copper sulphate solution, observe colour change to colourless, and filter to see reddish-brown copper deposit. They write a balanced equation and predict outcomes with iron instead. Discuss using reactivity series posters.

25 min·Pairs

Oxygen Reaction Comparison: Whole Class Demo

Teacher demonstrates burning magnesium ribbon for white ash and heating charcoal powder for pungent gas. Students predict and record oxide properties using litmus paper. Class discusses acidic vs basic nature and links to pollution from sulphur dioxide.

30 min·Whole Class

Non-metal Tests: Individual Observation Logs

Provide sulphur powder to heat gently and test product gas with limewater. Students log observations, compare with metal oxide tests from prior stations, and note differences in reactivity with water using litmus.

20 min·Individual

Real-World Connections

• Metallurgists use the reactivity series to select appropriate metals for specific applications, such as using corrosion-resistant metals like stainless steel (an alloy) for kitchen utensils and construction in coastal areas of Mumbai.
• Chemical engineers design processes for extracting metals from their ores, considering the reactivity of the metal. For instance, highly reactive metals like aluminium are extracted using electrolysis, a process different from that used for less reactive metals like iron, which is smelted in blast furnaces.

Assessment Ideas

Quick Check

Present students with a list of metal and non-metal oxides (e.g., MgO, SO2, CaO, CO2). Ask them to classify each as acidic or basic and write one sentence justifying their choice based on the element it's formed from.

Discussion Prompt

Pose the scenario: 'Imagine you have iron nails and copper sulphate solution. What do you predict will happen if you place the nails in the solution? Explain your prediction using the concept of reactivity.' Facilitate a class discussion on their predictions and reasoning.

Exit Ticket

Ask students to write down one metal and one non-metal. For each, they should describe its reaction (or lack of reaction) with dilute hydrochloric acid and the expected product, if any.

Frequently Asked Questions

How do metals and non-metals differ in reactivity with oxygen?

Metals form basic oxides, like magnesium oxide from burning magnesium, which turn red litmus blue. Non-metals form acidic oxides, such as sulphur dioxide from burning sulphur, which turn blue litmus red and react with bases. These differences arise from their position in the reactivity series and electron transfer tendencies, observable in simple classroom demos.

What products form when metals react with acids?

Reactive metals like zinc react with dilute HCl to form zinc chloride and hydrogen gas: Zn + 2HCl → ZnCl₂ + H₂. Less reactive metals like copper show no reaction. Students verify hydrogen by its pop sound with a burning splint, linking to the reactivity series for predictions.

Explain displacement reaction between metals.

A more reactive metal displaces a less reactive one from its salt solution, like zinc displacing copper: Zn + CuSO₄ → ZnSO₄ + Cu. The blue solution turns colourless with copper deposit. This follows the reactivity series and demonstrates single displacement in real time.

How can active learning help teach chemical properties of metals and non-metals?

Active learning through station rotations and paired demos lets students handle safe reactions, observe gas evolution or colour changes firsthand, and predict using reactivity series charts. Group discussions resolve misconceptions, while logging data builds evidence-based explanations. This approach makes abstract properties tangible, boosts engagement, and develops lab skills vital for CBSE practicals.