Lesson Notes By Weeks and Term v4 - JHS 3
MATERIALS
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MATERIALS
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Subject: Science
Class: JHS 3
Term: 1st Term
Week: 3
Grade code: B9.1.1.2.1
Strand code: 1
Sub-strand code: 1
Content standard code: B9.1.1.2
Indicator code: B9.1.1.2.1
Theme: DIVERSITY OF MATTER
Subtheme: MATERIALS
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Materials around us (salt, water, metals, plastics, charcoal, cement, soap) behave differently because their particles are held together in different ways. In Ghana, understanding chemical bonding helps learners explain why: salt (NaCl) dissolves in water and conducts electricity in solution (important for electrolytes and batteries), metals like aluminium and copper conduct electricity (wiring in homes, ECG, phone chargers), plastics and rubber do not conduct electricity (insulation for cables, slippers), diamond is very hard while graphite is soft (pencils).
2.1 Matter, atoms and why bonding happens Matter is anything that has mass and occupies space. Materials are forms of matter used for making things. Atoms are tiny particles that make up matter. Atoms have electrons arranged in shells (energy levels). Many atoms become more stable when their outermost shell (valence shell) is full. For JHS level, we use the idea that atoms “want” a stable arrangement like noble gases. Common stable patterns: 2 electrons in the first shell (e.g., helium-like) 8 electrons in the outer shell for many atoms (octet idea)
Chemical bonding results when atoms interact to become more stable by: Transferring electrons (ionic bonding), Sharing electrons (covalent bonding), Pooling/delocalising electrons in metals (metallic bonding).
2.2 Key definitions Chemical bond: the force of attraction that holds atoms or ions together in a substance. Ion: a charged particle formed when an atom gains or loses electrons. Cation (+): formed when an atom loses electrons (usually metals). Anion (−): formed when an atom gains electrons (usually non-metals). Valence electrons: electrons in the outermost shell that take part in bonding.
2.3 Ionic bonding (electron transfer) Where it occurs: between a metal and a non-metal. How it forms: electrons are transferred from the metal to the non-metal. Step-by-step example (Sodium chloride – common salt) Sodium (Na) is a metal. It has 1 valence electron. Chlorine (Cl) is a non-metal. It has 7 valence electrons. Sodium becomes stable by losing 1 electron. Chlorine becomes stable by gaining 1 electron.