Grade 8 Integrated Science Notes

Strand 1 & 2 – Simplified and Well-Structured Guide

📘 STRAND 1: MIXTURES, ELEMENTS & COMPOUNDS

1.1 Elements and Compounds

🔬 What Is Matter?

• Matter is anything that occupies space and has mass

• Matter is made up of:

  • Pure substances (elements and compounds)

  • Mixtures (uniform or non-uniform)

⚛ Elements

• An element is a pure substance that cannot be broken down into simpler substances by chemical or physical means

• Elements are the building blocks of matter

• Each element is made of atoms

• Atoms of the same element are identical

Examples of elements:

• Hydrogen (H)

• Oxygen (O)

• Iron (Fe)

• Sodium (Na)

🧪 Compounds

• A compound is a pure substance made when two or more elements chemically combine

• Compounds can be broken down into elements through chemical reactions

Examples:

• Water → H₂O (Hydrogen + Oxygen)

• Sodium Chloride (Salt) → NaCl (Sodium + Chlorine)

🔤 Chemical Symbols

Why Chemical Symbols Are Used

• Short and easy to write

• Universally recognized

• Save time for scientists

Rules of Writing Symbols

• First letter is capital

• Second letter (if any) is small

📌 Examples of Symbols from English Names

📌 Symbols from Latin Names

🧬 Chemical Formulae

• A chemical formula shows:

  • Elements present

  • Their ratio in the compound

Examples:

• Water → H₂O (2 Hydrogen : 1 Oxygen)

• Salt → NaCl (1 Sodium : 1 Chlorine)

🥗 Application of Elements in Daily Life

Food Nutrients

Food nutrients are chemical compounds made of elements such as carbon, hydrogen, oxygen, and nitrogen.

Main food nutrients include:

• Proteins

• Fats

• Carbohydrates

• Vitamins

• Mineral salts

🧾 Mineral Elements and Food Sources

🧼 Elements in Toiletries

• Toothpaste → Fluoride compounds

• Soaps & detergents → Potassium compounds

• Body lotion → Sodium compounds

🏅 Importance of Some Elements

Gold

• Precious metal

• Used in jewellery

• Does not rust or corrode

Silver

• Used in jewellery and cutlery

• Used in medals

Iron

• Strong and durable

• Used in construction

• Steel = Iron + Carbon

📦 Information on Packaging Labels

Packaging labels show elements and compounds present in products.

Examples:

• Toothpaste → Sodium fluoride

• Bottled water → Calcium, Magnesium, Potassium

• Baking powder → Sodium compounds

🔥 Physical and Chemical Changes

Physical Changes

• Change in shape, size, colour, or state

• Reversible

• No new substance formed

Example: Heating and cooling an iron pin

Chemical Changes

• New substances are formed

• Irreversible

• Permanent changes

Examples:

• Burning magnesium ribbon

• Digestion of food

• Rusting of iron

🔥 Classes of Fire

🧯 Fire Control Measures

To control fire, remove one part of the fire triangle:

• Fuel

• Heat

• Oxygen

Common fire extinguishers:

• Water extinguisher (Class A)

• CO₂ extinguisher (Class B & E)

• Foam extinguisher

• Powder extinguisher

🌱 STRAND 2: LIVING THINGS & THEIR ENVIRONMENT

2.1 The Cell

What Is a Cell?

• A cell is the basic unit of life

• Living organisms can be:

  • Unicellular (one cell)

  • Multicellular (many cells)

🔬 Plant vs Animal Cells

Similarities

• Cell membrane

• Cytoplasm

• Nucleus

Differences

🧠 Functions of Cell Structures

🔍 Magnification of Cells

Formula:

Total Magnification = Eyepiece × Objective Lens

Example:
10 × 4 = ×40

2.2 Movement of Materials in and Out of the Cell

Diffusion

• Movement of particles from high concentration to low concentration

• Does not require energy

Examples:

• Smelling perfume

• Oxygen entering blood

Osmosis

• Movement of water molecules

• Through a semi-permeable membrane

• From dilute to concentrated solution

Importance:

• Water absorption in plants

• Excretion in animals

• Support in plants

Diffusion vs Osmosis

2.3 Human Reproduction – Menstrual Cycle

What Is the Menstrual Cycle?

• Monthly changes preparing the female body for pregnancy

• Lasts 28–35 days

• Controlled by hormones

Phases of the Menstrual Cycle

⚠ Challenges

• Irregular periods

• Cycle length shorter than 21 days or longer than 35 days