Grade9||Metals and Non-Metals||Notes

Matter is anything that has mass and occupies space. Some matter exists in the form of elements.

Element: A pure substance made up of only one kind of atom.

Classification of Elements

Elements are classified into three groups:

1. Metals
2. Non-metals
3. Metalloids

Among these, metals are widely used in daily life. Metals are used to make utensils, vehicles, machines, and electrical devices. Metals are found either in the free state (pure form) or in the combined state as ores.

Some metals are essential for living organisms. Iron is present in human blood and magnesium is present in chlorophyll of plants. Therefore, the study of metals is important.

2. Properties of Metals

The properties of metals are divided into:

1. Physical properties
2. Chemical properties

3. Physical Properties of Metals

3.1 Malleability

Definition: The property of metals by which they can be beaten into thin sheets is called malleability.

Examples: Iron, copper, aluminium, gold

Reason: Metallic bonds do not break when hammered; instead, metal atoms slide over one another.

Non-metals like sulphur and coal are brittle and break into pieces when hammered.

3.2 Ductility

Definition: The property of metals by which they can be drawn into thin wires is called ductility.

Examples: Copper wire, aluminium wire

Reason: Metallic bonding allows atoms to stretch without breaking.

3.3 Conductivity of Electricity

Definition: Metals allow electric current to pass through them easily.

Examples: Copper, aluminium, iron

Reason: Metals contain free electrons that move easily and carry electric current.

Non-metals are poor conductors of electricity.

3.4 Conductivity of Heat

Definition: Metals transfer heat easily from one end to another.

Examples: Steel spoon, iron rod

Reason: Free electrons in metals help in the transfer of heat energy.

Non-metals like wood and plastic are poor conductors of heat.

3.5 Sonorous Nature

Definition: The property of metals by which they produce a ringing sound when struck is called sonorous nature.

Examples: Bell, gong, metal plates

3.6 Hardness

Definition: Most metals are hard and strong and cannot be cut or scratched easily.

Examples: Iron, copper

Exceptions:

Sodium and potassium are soft metals.

Diamond is a non-metal but the hardest known substance.

3.7 High Melting and Boiling Points

Definition: Most metals have high melting and boiling points.

Reason: Strong force of attraction exists between metal atoms.

Non-metals generally have low melting and boiling points.

4. Chemical Properties of Metals

4.1 Reaction with Oxygen

Definition: Metals react with oxygen to form metallic oxides which are basic in nature.

General Reaction: Metal + Oxygen → Metal Oxide

Examples: 2Mg + O₂ → 2MgO 4Fe + 3O₂ → 2Fe₂O₃ 2Cu + O₂ → 2CuO

4.2 Reaction with Dilute Acids

Definition: Reactive metals react with dilute acids to form salt and hydrogen gas.

General Reaction: Metal + Dilute Acid → Salt + Hydrogen Gas

Example: Mg + 2HCl → MgCl₂ + H₂

4.3 Reaction with Water

Definition: Highly reactive metals react with water to form metallic hydroxide and hydrogen gas.

Examples: 2Na + 2H₂O → 2NaOH + H₂ Ca + 2H₂O → Ca(OH)₂ + H₂

Precaution: Sodium and potassium are highly reactive and should not be handled with bare hands.

5. Differences Between Metals and Non-metals

PropertyMetalsNon-metalsMalleabilityMalleableNot malleableDuctilityDuctileNot ductileConductivityGood conductorPoor conductorHeat conductionGoodPoorMelting & boiling pointHighLowHardnessMostly hardMostly soft

6. Essential Metals Required for Human Body

6.1 Zinc (Zn)

Sources: Seeds, cereals, nuts, milk, meat, fish, eggs

Advantages:

1. Increases immunity
2. Helps wound healing
3. Helps in DNA and protein formation

Deficiency Effects:

1. Hair fall
2. Weak immunity
3. Slow wound healing

6.2 Iron (Fe)

Sources: Spinach, cereals, meat, fish

Advantages:

1. Transports oxygen in blood
2. Helps respiration
3. Prevents anemia

Deficiency Effects:

1. Anemia
2. Fatigue
3. Breathing difficulty

6.3 Sodium (Na)

Sources: Table salt, meat, eggs

Advantages:

1. Maintains water balance
2. Helps nerve and muscle function

Deficiency Effects:

1. Muscle cramps
2. Vomiting
3. Fainting

6.4 Potassium (K)

Sources: Banana, avocado, vegetables, milk, curd

Advantages:

1. Controls blood pressure
2. Supports nervous system

Deficiency Effects:

Muscle weakness

Constipation

High blood pressure

7. Harmful Effects of Mercury and Lead

7.1 Lead (Pb)

Uses: Batteries, paints, radiation shielding

Harmful Effects:

1. Brain damage
2. Anemia
3. Weak bones
4. Developmental problems in children

7.2 Mercury (Hg)

Uses: Thermometer, barometer, tube light

Harmful Effects (Mercurialism):

1. Brain damage
2. Kidney and lung damage
3. Harmful to unborn babies

8. Conclusion

Metals and non-metals play an important role in our daily life. Metals are widely used due to their physical and chemical properties. Some metals are essential for the human body, while others like mercury and lead are harmful. Therefore, proper knowledge and safe use of metals are necessary.