Grade 8 INTEGRATED SCIENCE Study Notes

Protons, Electrons and Neutrons

The atom is made of three even smaller particles called subatomic particles.

In a normal atom, the number of protons equals the number of electrons. The positive and negative charges cancel out, so the atom has no overall charge.

Atoms can be split into subatomic particles, but only through special processes — not by ordinary chemistry.

Key Points

• Proton — positive charge, inside the nucleus.
• Neutron — no charge, inside the nucleus.
• Electron — negative charge, orbits outside the nucleus.
• Protons = electrons → atom has no overall charge.

What is an Element?

An element is a pure substance made of only one type of atom.

Because all its atoms are the same, an element cannot be broken down into anything simpler by ordinary chemistry.

Examples: oxygen (all oxygen atoms), gold (all gold atoms), iron, carbon, hydrogen.

What is a Molecule?

Some atoms cannot exist on their own — they join together to form small groups. These groups are called molecules.

A molecule is the smallest particle of an element or a compound that can exist on its own.

Molecules can be made of:

• Same-type atoms — molecule of an element (e.g. two oxygen atoms form O₂)
• Different-type atoms — molecule of a compound (e.g. hydrogen + oxygen form water)

Strand Overview

In earlier grades you learned that matter has mass and takes up space. In this strand you will find out what matter is actually made of — from the tiniest particle inside an atom all the way to how elements are used in everyday life.

What is an Atom?

All matter is made of very tiny particles called atoms.

An atom is the smallest particle of an element that still has the properties of that element. Atoms are too small to see, even with a school microscope.

Every atom has two parts:

• A nucleus at the centre
• Electrons moving around the nucleus in paths called orbits

The nucleus contains two types of particles — protons and neutrons.

Key Points

• An atom is the smallest particle of an element with the properties of that element.
• Every atom has a nucleus (centre) and electrons orbiting outside it.

What is a Compound?

A compound is a pure substance made of two or more different types of atoms chemically combined.

A compound has completely different properties from the elements that made it.

Examples:

• Carbon (IV) oxide — one carbon atom + two oxygen atoms bonded together
• Water — hydrogen atoms + oxygen atom combined
• Table salt (sodium chloride) — sodium + chlorine atoms combined

Atoms vs. Molecules

Key Points

• An atom is a single particle of one element.
• A molecule is two or more atoms joined together.
• Same-type atoms → molecule of an element. Different-type atoms → molecule of a compound.

Element vs Compound

Key Points

• Both elements and compounds are made of atoms — the difference is the type of atoms.
• Element → one type of atom. Compound → two or more different types, chemically combined.

Why We Use Chemical Symbols

Every element has a name, but names differ in every language. To solve this, each element is given a chemical symbol — a short code of one or two letters that means the same element in every country.

Using symbols is faster and avoids writing long names every time a reaction is described.

Rule 2: Two-Letter Symbols

Some elements share the same first letter. For example, both carbon and calcium start with C. To tell them apart, a second letter is added.

Rule 2: First letter capital, second letter lower case, taken from the English name.

Ca is correct. CA is wrong (second letter must be lower case). ca is wrong (first letter must be capital).

Key Points

• Rule 2: shared first letter → first capital + second lower case, from the English name (Ca, Cl, Al, Mg, He, Li, Be, Zn).

Rule 3: Symbols from Latin Names

Some symbols look nothing like the English name. This is because they come from the element's Latin name — the name used by scientists long ago when Latin was the shared language of science.

The same rule applies: first letter capital, second letter lower case.

Memory tips: Fe = iron fences. Na = sodium in table salt. Au = gold is authentic. Cu = copper carries current. Pb = plumbers once used lead (Plumbum) pipes.

Key Points

• Rule 3: symbol from Latin name → first capital + second lower case (Fe, Cu, Na, Au, Ag, Hg, Pb).
• Latin was the shared language of science — elements known in ancient times kept their Latin-derived symbols.

All Three Rules — Quick Reference

Rule 1: One Capital Letter

When an element's first letter is unique, the symbol is just that one letter, written as a capital.

Always use a capital letter. Writing h or o is wrong. Only H and O are correct.

Key Points

• Chemical symbols are the same in every country.
• Rule 1: unique first letter → one capital letter (H, O, C, N).

Full Reference Table

The blank cells (Aluminium and Tin) are for you to fill in before checking the answers below.

Answers: Aluminium → Al (Rule 2). Tin → Sn (Rule 3, from Latin Stannum).

Spotting Wrong Symbols

Check three things in order:

1. Is the first letter a capital? If not — wrong.
2. Is the second letter (if there is one) lower case? If not — wrong.
3. Is the symbol taken from the correct name (English or Latin)? If not — wrong.

Example: FE for iron — second letter should be lower case. Correct: Fe.
fe for iron — first letter should be a capital. Correct: Fe.

Key Points

• All three rules share the same pattern: first capital, second lower case.
• The only difference is which name the letters come from.

What the Arrow Means

The arrow (→) in a word equation shows the direction of the reaction — from what you start with (reactants) to what you end up with (products). It means 'produces.'

Without the arrow, the equation is incomplete. Word equations are also useful because they let scientists describe reactions simply and clearly without drawing every single atom.

What is a Word Equation?

When elements react to form a compound, we can show this using a word equation.

A word equation uses the full names of substances and an arrow (→) that means 'produces' or 'reacts to form.'

Structure: Reactants → Products

• Reactants — the elements that react (written on the left of the arrow)
• Products — the compound formed (written on the right of the arrow)

Reading All Five Equations

Key Points

• Arrow (→) = 'produces' = direction of the reaction.
• Left side = reactants (elements). Right side = product (compound).

Five Key Word Equations

Key Points

• Elements are always on the left. The compound is always on the right.
• The arrow (→) means 'produces.'

Why Elements Have Different Values

The value of an element depends on two things: how useful it is and how available it is.

Gold is very valuable because it is useful and rare — it is not easy to find or obtain.

Elements are applied in four main areas of society:

1. Jewellery, trophies and medals — precious elements like gold and diamond
2. Construction and electrical applications — iron, aluminium, silicon, copper
3. Mineral elements in food — sodium, potassium, calcium, magnesium, sulphur, phosphorus
4. Packaging labels — elements and compounds listed on everyday products

Key Points

• Value = usefulness + availability. Rare + useful = more valuable.
• Elements are used in four main areas: jewellery/medals, construction/electricity, food, and packaging labels.

Jewellery, Trophies and Medals

Jewellery, trophies, and medals are made from precious elements and compounds such as gold and diamond.

These elements are chosen because they are:

• Rare — not found in large quantities on Earth
• Unique in appearance — gold has a bright yellow metallic shine; diamond is clear and brilliant
• Expensive to obtain — mining and purifying them takes great effort and cost

Key Points

• Gold and diamond are chosen for jewellery and awards because they are rare, beautiful, and expensive to obtain.

Elements in Construction

Iron (Fe) is combined with carbon to make steel — a material that is strong and durable. Steel is used in iron sheets, pipes, nails, bridges, and electricity pylons.

Aluminium (Al) is lightweight and does not rust easily. It is used in aeroplane parts and window frames.

Silicon (Si) is found in sand, clay, and stone. It is used to make concrete and glass.

Mineral Elements in Food

Elements are also found inside the food we eat. The body needs mineral elements for specific health functions.

Foods rich in these mineral elements have a higher nutritional and market value.

Key Points

• Six mineral elements in food: Na, K, Mg, Ca, S, P.
• Each has a specific role in keeping the body healthy.
• Foods rich in these elements have higher nutritional and market value.

What Packaging Labels Tell Us

Elements and compounds are found in all products we use. Manufacturers list them on the packaging label — the printed information on the bottle, tube, tin, or carton.

A label shows:

• The elements and compounds in the product
• The quantity of each one

Elements in Everyday Household Items

Almost everything at home contains one or more elements. The element used affects how well the item works and how much it costs.

How to Read a Label and Why It Matters

When Jayden read his toothpaste tube, he saw calcium carbonate and fluoride.

• Calcium carbonate contains calcium (Ca) — good for teeth and bones.
• Fluoride contains fluorine (F) — strengthens tooth enamel.

Manufacturers include this information so users can:

1. Know what the product contains
2. Know how to use it correctly
3. Be aware of any dangers associated with the product

Key Points

• Packaging labels list elements and compounds so users know what is inside, how to use it, and what dangers it may have.

How Elements Affect Value

Elements affect the value of household items in two ways:

• Functional value — the right element makes the item work better. Copper wires conduct electricity better than iron wires, so copper wire is preferred even though it costs more.
• Monetary value — rare elements make items more expensive. A gold ring costs far more than an aluminium ring of the same size because gold is a rare, precious element.

Elements in Electrical Applications

Copper (Cu) and aluminium (Al) are good conductors of electricity — electric current flows through them easily. They are used for electrical wires and parts of electrical appliances.

Rubber and plastics are used to cover the wires. These coverings are insulators — they stop electricity from flowing where it should not go and protect people from electric shock.

Key Points

• Iron → steel: strong and durable (bridges, iron sheets, pylons).
• Aluminium: lightweight, does not rust (aeroplanes, window frames).
• Silicon: used in concrete and glass.
• Copper and aluminium: conductors of electricity (wires).
• Rubber and plastic: insulators — protect people from electric shock.

Extended Activity

Your task:

1. Walk around your home and identify at least five items.
2. For each item, name the element or compound used to make it.
3. Explain how that element affects the item's value — does it make it work better? Does it make it more expensive?
4. Write your findings in your notebook.
5. Share your findings with your classmates.

Complete this assignment carefully and on time — take responsibility for your own learning.

Key Points

• Functional value: the right element makes an item work better (e.g., copper in wiring).
• Monetary value: rare elements make items more expensive (e.g., gold jewellery).

Revision: Atoms, Elements, Compounds and Molecules

You have covered all of Sub-Strand 1.1. Use these summaries to review, then test yourself with confidence.

• An atom is the smallest particle of an element with the properties of that element. It has a nucleus (protons + neutrons) and electrons orbiting outside.
• An element is a pure substance made of only one type of atom.
• A compound is a pure substance made of two or more different types of atoms chemically combined.
• A molecule is the smallest particle of an element or compound that can exist on its own.

End of Sub-Strand Assessment

This assessment covers all of Sub-Strand 1.1. Work through each question on your own before checking the answers.

Sub-Strand 1.1 — Key Points Summary

• An atom is the smallest particle of an element with the properties of that element.
• Every atom has a nucleus (protons + neutrons at the centre) and electrons orbiting outside.
• An element has only one type of atom — it cannot be broken down by ordinary chemistry.
• A compound has two or more different types of atoms chemically combined.
• A molecule is the smallest particle of an element or compound that can exist on its own.
• Rule 1: unique first letter → one capital (H, O, C, N).
• Rule 2: shared first letter → first capital + second lower case from English name (Ca, Cl, Al).
• Rule 3: from Latin name → first capital + second lower case (Fe, Cu, Na, Au, Ag, Hg, Pb).
• Word equation: Reactants → Products. The arrow (→) means 'produces.'
• Five reactions: Sodium + Chlorine → Sodium chloride; Hydrogen + Oxygen → Water; Carbon + Oxygen → Carbon (IV) oxide; Copper + Oxygen → Copper oxide; Aluminium + Oxygen → Aluminium oxide.
• Precious elements (gold, silver, diamond) are rare, unique, and expensive to obtain.
• Iron → steel (strong); aluminium (lightweight, no rust); silicon (concrete, glass); copper and aluminium (conductors); rubber and plastic (insulators).
• Mineral elements in food: Na, K, Mg, Ca, S, P — each with a specific role in the body.
• Packaging labels help users know what a product contains, how to use it, and what dangers it may have.

Revision: Chemical Symbols

• Rule 1 — unique first letter → one capital: H, O, C, N
• Rule 2 — shared first letter → first capital + second lower case (English): Ca, Cl, Al, Mg
• Rule 3 — from Latin name → first capital + second lower case: Fe (Ferrum), Cu (Cuprum), Na (Natrium), Au (Aurum), Ag (Argentum), Hg (Hydrargyrum), Pb (Plumbum)

Revision: Word Equations

Structure: Reactants → Products. The arrow (→) means 'produces.'

• Sodium + Chlorine → Sodium chloride
• Hydrogen + Oxygen → Water
• Carbon + Oxygen → Carbon (IV) oxide
• Copper + Oxygen → Copper oxide
• Aluminium + Oxygen → Aluminium oxide

Revision: Applications of Common Elements

Key Points

• Review all four summaries above before attempting the mixed self-test.