Chemistry and Chemical Reactions Lecture Notes

Displacement Reactions and the Reactivity Series (12 May 2026)

A displacement reaction is a chemical process where a more reactive element takes the place of a less reactive element in a compound. This principle is governed by the reactivity series of metals.

The Reactivity Series

The elements are ordered from most reactive to least reactive as follows:

1. Potassium

2. Sodium

3. Calcium (Extracted only through electrolysis)

4. Magnesium

5. Alimunium

6. Carbon

7. Zinc

8. Iron

9. Dead

10. Hydogon

Displacement Mechanics

• These elements can be displaced by others depending on their position in the reactivity series.

• Example Reaction:   $\text{alimunium} + \text{oxide} \rightarrow \text{alimunium oxide} + \text{Iron}$   In this reaction, alimunium displaces the iron to form alimunium oxide.

Reactivity Observations with Water and Acids (12 May 2026)

The reactivity of metals such as Calcium, Iron, and Copper is observed by their reactions with water, dilute acid, and concentrated acid.

• Observation Method: Reactivity is measured by the presence of bubbles or fizzing (effervescence).

• Observations:   - Calcium: Shows high reactivity with water and acids.   - Iron: Shows moderate reactivity.   - Copper: Displays the lowest reactivity among the three mentioned.

Elements vs Compounds (21 April 2016)

Notes from the session titled "Jushid":

• Elements: These consist of only one type of atom. They are listed on the Periodic Table.

• Compounds: These are substances formed when two or more different types of atoms are chemically bonded together.

• Structure of the Periodic Table: Elements are organized into 8 groups, with transition metals located in the middle.

Variation, Photosynthesis, and Catalysts (March 2020 & 14 April 2026)

Variation

Variation in organisms is caused by two main factors:

1. Environmental factors: Influence from the surroundings.

2. Inherited/Genetic factors: Traits passed down from parents (e.g., nutrition).

Photosynthesis

This process is used by plants to produce food in the form of energy.

Chemical Reactions and Catalysts

A catalyst is a substance used to speed up a chemical reaction without being used up itself.

• Advantages:   - Only a small amount is required.   - They allow products to be produced much more quickly.

• Disadvantages:   - They can be very expensive.   - Different reactions require different catalysts (they are not universal).

Demonstration: Elephant Toothpaste

This is a rapid decomposition of hydrogen peroxide ($H_2O_2$) into water ($H_2O$) and oxygen ($O_2$), which can be accelerated with a catalyst. $\text{Elephant Toothpaste Demo: } 2H_2O_2 \rightarrow 2H_2O + O_2$

Exothermic and Endothermic Reactions

Exothermic Reactions

• These reactions release energy into the surroundings.

• Example: The "Elephant Toothpaste" demonstration is exothermic as energy (heat) is released.

• Observation: A flaming bypass was shared when energy was being released.

Endothermic Reactions

• These reactions take in energy from the surroundings, causing a drop in temperature.

• Demonstration 1: Citric acid and sodium hydrogen carbonate.

• Demonstration 2: Barium hydroxide and ammonium chloride mixture.   - Procedure: Water was placed on a wooden board, and the beaker was placed on top.   - Result: The reaction was so endothermic that it froze the water, sticking the beaker to the board.

Oxidation and Thermal Decomposition (10 March 2020)

Oxidation of Magnesium

$\text{Magnesium} + \text{Oxygen} \rightarrow \text{Magnesium Oxide} (MgO)$

Thermal Decomposition

This occurs when a substance is heated so intensely that it breaks down into simpler substances.

• Experiment: Heating copper carbonate using a delivery tube.

• Reaction:   $\text{Copper Carbonate} \rightarrow \text{Copper Oxide} (CuO) + \text{Carbon Dioxide} (CO_2)$

• Test: The identity of the carbon dioxide gas is confirmed when it turns limewater cloudy.

Combustion (2 December)

Combustion is the scientific term for burning. It requires three components, known as the Fire Triangle:

1. Heat

2. Oxygen

3. Fuel

Safety Note: Fire can be extinguished by removing one of these components, such as covering it with sand to remove oxygen.

Complete and Incomplete Combustion (16 December 2025)

Complete Combustion

This occurs when there is a plentiful supply of oxygen.

• Bunsen Burner Setting: Air hole open (air is drawn into the chimney).

• Flame: Very hot, blue flame.

• Equation:   $\text{Methane} + \text{Oxygen} \rightarrow \text{Carbon Dioxide} + \text{Water}$   $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$

Incomplete Combustion

This occurs when there is a limited supply of oxygen.

• Bunsen Burner Setting: Air hole closed.

• Flame: Yellow flame, which transfers less heat than the blue flame.

• Products: Carbon (soot), Carbon Monoxide ($CO$), and Water ($H_2O$).

• Equation:   $\text{Methane} + \text{Oxygen} \rightarrow \text{Carbon} + \text{Carbon Monoxide} + \text{Water}$

Air Pollution and Environmental Impact (January 2026)

Burning fossil fuels leads to the release of several pollutants:

• Carbon Dioxide ($CO_2$): From cars and factories; contributes to global warming.

• Sulfur Dioxide ($SO_2$): From coal impurities; causes acid rain and asthma.

• Carbon Particulates: Soot in smoke; causes lung damage.

• Nitrogen Monoxide/Dioxide ($NO/NO_2$): Produced inside car engines; leads to smog and respiratory issues.

• Carbon Monoxide ($CO$): Result of faulty heaters/incomplete combustion; toxic gas that reduces the oxygen-carrying capacity of blood.

Conservation of Mass (24 February)

In a chemical reaction, no atoms are destroyed; they only change how they are bonded.

• Experiment: Comparing the mass of a Tin lid + Iron wool vs. a Tin lid + Iron oxide.

• Result: Oxygen is gained during the reaction, increasing the final mass recorded in grams ($g$).

Crystallization (4 November 2025)

Procedure: Recovering Copper Sulfate

1. Heat sulfuric acid and add copper oxide (black solid).

2. Reaction: $\text{Copper Oxide} + \text{Sulfuric Acid} \rightarrow \text{Copper Sulfate} + \text{Water}$.

3. A blue solution forms.

4. Filter the solution to remove any unreacted black copper oxide.

5. Allow the blue solution to cool, forming copper sulfate crystals.

Solution Chemistry Definitions (11 November)

• Solute: The substance that dissolves.

• Solvent: The substance that dissolves the solute.

• Solution: A mixture of solute and solvent.

• Mixture: Two or more substances not chemically combined.

• Dilute: Contains a small amount of solute compared to solvent.

• Concentrated: Contains a large amount of solute.

Reactions of Acids (October 2025)

Acids and Metal Carbonates (21 October 2025)

General Equation: $\text{Metal Carbonate} + \text{Acid} \rightarrow \text{Salt} + \text{Carbon Dioxide} + \text{Water}$

• Specific Reactions:   - $\text{Sodium Carbonate} + \text{Nitric Acid} \rightarrow \text{Sodium Nitrate} + \text{Carbon Dioxide} + \text{Water}$   - $\text{Calcium Carbonate} + \text{Nitric Acid} \rightarrow \text{Calcium Nitrate} + \text{Carbon Dioxide} + \text{Water}$   - $\text{Zinc Carbonate} + \text{Sulfuric Acid} \rightarrow \text{Zinc Sulfate} + \text{Carbon Dioxide} + \text{Water}$

• Reaction Speeds: Sodium, Copper, and Potassium carbonates all react "Fast" with Sulfuric, Hydrochloric, and Ethanoic acids.

Acids and Metals (14 October 2025)

General Equation: $\text{Metal} + \text{Acid} \rightarrow \text{Salt} + \text{Hydrogen Gas}$

• Specific Reactions:   - $\text{Ethanoic Acid} + \text{Magnesium} \rightarrow \text{Magnesium Ethanoate} + \text{Hydrogen}$   - $\text{Nitric Acid} + \text{Magnesium} \rightarrow \text{Magnesium Nitrate} + \text{Hydrogen}$   - $\text{Nitric Acid} + \text{Calcium} \rightarrow \text{Calcium Nitrate} + \text{Hydrogen}$

Acids and Hydroxides (Neutralization)

• $\text{Sodium Hydroxide} + \text{Sulfuric Acid} \rightarrow \text{Sodium Sulfate} + \text{Water}$

• $\text{Potassium Hydroxide} + \text{Hydrochloric Acid} \rightarrow \text{Potassium Chloride} + \text{Water}$

• $\text{Magnesium Hydroxide} + \text{Nitric Acid} \rightarrow \text{Magnesium Nitrate} + \text{Water}$

• $\text{Nickel (II) Oxide} + \text{Sulfuric Acid} \rightarrow \text{Nickel Sulfate} + \text{Water}$

Neutralization and Indicators (September - October 2025)

Neutralization

A chemical reaction between an acid and an alkali resulting in a pH of 7. $\text{Acid} + \text{Alkali} \rightarrow \text{Salt} + \text{Water}$ $\text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O}$

Common Classroom Chemicals

1. Hydrochloric Acid ($HCl$)

2. Sodium Hydroxide ($NaOH$)

3. Sulphuric Acid ($H_2SO_4$)

4. Ammonia ($NH_3$)

5. Nitric Acid ($HNO_3$)

Universal Indicator and pH Scale (30 September 2025)

Universal indicator shows a range of colors corresponding to pH values:

• pH 1-2: Red (Most acidic)

• pH 3-4: Orange/Yellow (Slightly acidic)

• pH 7: Green (Neutral)

• pH 8-11: Turquoise/Blue (Slightly alkaline)

• pH 12-14: Dark Purple (Most alkaline)

Litmus and Red Cabbage Indicators

• Red Cabbage: Turns Pink/Red in acid, Green/Yellow/Blue in alkali.

• Red Litmus Paper: Stays Red in acid, turns Blue in alkali.

• Blue Litmus Paper: Turns Red in acid, stays Blue in alkali.

Domestic Acids and Alkalis (9 September 2025)

• Acids: Cola, rain, coffee, lemon, orange juice, vinegar.

• Alkalis: Oven cleaner, toothpaste, baking soda, soap, indigestion tablets, bleach.