FOUNDATIONS OF CHEMISTRY FOR YOUNG STARS - Lesson 17: Solutions, Solubility, and Factors Affecting Solubility – Why Some Things Dissolve and Others Don’t
💧 Light for the Living – Science that Breathes with the Village
Lesson 17: Solutions, Solubility, and Factors Affecting Solubility – Why Some Things Dissolve and Others Don’t
📍 Scene: Barkin Kogi, Plateau State
👨🏾🏫 Main Character: Teacher Dung, the Miner’s Teacher
🏞️ Scene 1 – “The Tea That Wouldn’t Mix”
It was a chilly morning in Barkin Kogi, a quiet mining village tucked between the misty hills of Plateau State. The miners were already by the river, washing tin ore in wide metal pans, their songs mixing with the sound of rushing water.
Inside a small mud-walled classroom, Teacher Dung stood before his students with a kettle of hot water, a spoon of sugar, a pinch of salt, and one shiny pebble from the mine.
“Today, my children,” he began with a smile, “we shall learn why some things dissolve easily — like good friends — while others refuse to mix, like quarrelling neighbours.”
The class burst into laughter.
Little Nanret raised her hand.
“Sir, when my mama makes tea, the sugar disappears, but the stones in our soup pot never disappear. Why?”
Teacher Dung chuckled.
“Ah, Nanret, that’s exactly what chemistry calls solubility — the ability of a substance to dissolve in a liquid.”
🍵 1. What Is Solubility?
He poured hot water into a tin cup and added sugar. The children leaned closer as the sugar disappeared.
“When something mixes completely with a liquid to form a clear, uniform mixture, we say it has dissolved. The mixture is called a solution.”
He wrote neatly on the chalkboard:
Then he explained:
-
Solute → the substance that dissolves (like sugar)
-
Solvent → the liquid that does the dissolving (like water)
-
Solution → the sweet mixture that results
He grinned.
“So, when Mama Nanret makes tea, sugar is the solute, water is the solvent, and the sweet tea is the solution. Simple!”
🪨 2. Why Some Substances Dissolve and Others Don’t
Next, Teacher Dung dropped a small stone into another cup of water. It sank and sat stubbornly at the bottom.
“See this? The stone refuses to dissolve because its particles are packed tightly together — like miners at payday!”
The class laughed again.
“But sugar dissolves because its particles are looser and can mix easily with water. Every solute has its own kind of friendship with a solvent.
If they like each other, they mix well. If not — they stay apart!”
He winked.
“Just like villagers who don’t speak the same language.”
🌡️ 3. Factors Affecting Solubility
Teacher Dung drew four simple pictures on the blackboard — a flame 🔥, a stirring spoon 🥄, a heap of fine salt 🧂, and a bowl of palm oil 🛢️.
“Now, let’s see what makes something dissolve faster or slower.”
(i) Temperature
He pointed to the flame.
“When water is heated, its particles move faster. They hit the solute more often, helping it dissolve quicker.
That’s why sugar melts faster in hot tea than in cold zobo.”
He poured sugar into two cups — one warm, one cold. The warm cup cleared first.
“See? Heat helps!”
(ii) Stirring or Agitation
He stirred with a spoon.
“When you stir, you help the solute spread throughout the solvent — just like miners shake their pans so that the lighter sand washes away quickly.”
(iii) Particle Size
He showed two bowls of salt — one coarse, one fine.
“Smaller particles dissolve faster because more of them touch the water at once.
That’s why granulated sugar dissolves faster than sugar cubes.”
(iv) Nature of Solute and Solvent
He lifted a small bottle of palm oil and poured it into water. The oil floated.
“Now, look here — oil and water will never be friends.
In chemistry, we say like dissolves like.
Polar solvents like water dissolve polar solutes like salt and sugar.
Non-polar solvents like oil dissolve things like grease or kerosene.”
The children laughed as they saw the oil floating lazily on top.
“No matter how much you stir, these two will never marry,” Teacher Dung said.
⛏️ 4. The Miners’ Lesson
Outside, the miners’ rhythmic splashing echoed from the riverbank. Teacher Dung pointed toward them.
“Do you see those miners? They depend on solubility every day!
The light, soluble sand gets carried away by the water, while the heavier tin stones stay behind.”
He smiled proudly.
“That’s chemistry at work — in our rivers, in our washing pans, even in your tea cups.”
🧮 5. Quantitative Idea of Solubility
He then wrote on the board:
“This shows how many grams of a substance can dissolve in 100 grams of water at a certain temperature.”
Example 1:
If 20 g of salt dissolves in 100 g of water at 30°C,
→ Solubility = 20 g per 100 g water.
Example 2:
At 50°C, 36 g dissolves instead.
“So, the warmer the water, the more salt it can hold.”
🌬️ 6. Summary Table – What Affects Solubility
|
Factor |
Effect on Solubility |
Example |
|
Temperature |
Solids dissolve faster in hot water |
Sugar in tea |
|
|
||
|
Stirring |
Increases rate of dissolving |
Mixing zobo |
|
Particle size |
Smaller particles dissolve faster |
Granulated vs. rock salt |
|
Nature of solute/solvent |
Some pairs dissolve, others don’t |
Oil and water |
|
Pressure (for gases) |
Gases dissolve more at high pressure |
Soft drinks fizz |
🍶 7. Real-Life Solubility in Barkin Kogi
Teacher Dung loved connecting science to village life. He listed examples the children knew well:
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Cooking: Salt and maggi dissolve easily in soup, but pepper oil floats on top.
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Medicine: Local herbs release their flavour faster in hot water than in cold.
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Soap-Making: Lye (NaOH) dissolves in water before mixing with oil to form soap.
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Mining: Water carries away soluble soil but leaves behind heavy, insoluble tin stones.
“So, you see,” he said, “solubility isn’t just for laboratories — it lives right here in our kitchens, farms, and rivers.”
📘 8. Practice Exercises
A. Fill in the Blanks
1️⃣ The ability of a substance to dissolve in a solvent is called __________.
2️⃣ The substance that dissolves is the __________.
3️⃣ Solubility increases when the __________ of the solvent is raised.
4️⃣ Oil and water do not mix because they have different __________.
B. Solve These
1️⃣ 15 g of sugar dissolve in 100 g of water at 25°C. What is the solubility?
2️⃣ Why does granulated salt dissolve faster than salt lumps?
3️⃣ Mention three ways to increase how fast a solid dissolves in water.
4️⃣ Why does heating increase solubility for solids but decrease it for gases?
💧 9. Key Points Summary
|
Concept |
Explanation |
|
Solubility |
Maximum amount of solute that dissolves in a solvent at a certain
temperature |
|
Solvent |
The liquid doing the dissolving |
|
Solute |
The substance that dissolves |
|
Solution |
The uniform mixture of solute and solvent |
|
Factors Affecting Solubility |
Temperature, stirring, particle size, nature of solute/solvent, and
pressure |
💬 10. Moral Reflection
As the cool Plateau breeze drifted through the windows, Teacher Dung closed his lesson softly:
“Children, solubility teaches us patience and harmony. Some things mix quickly, others resist — yet each has its purpose. Life is like that too: we can’t all blend the same way, but we can still work together.”
Nanret smiled shyly.
“So, sir… people are like solutes and solvents — some mix well, some stay apart?”
Teacher Dung laughed heartily.
“Exactly! But wisdom, my dear, is knowing when to stir.”
The class erupted in laughter, and the miners by the river cheered at the sound of learning drifting on the Plateau wind.
🧠 Lesson Summary
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Solubility = how much of a substance can dissolve in a given solvent.
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Factors: temperature, stirring, particle size, and nature of solute/solvent.
-
“Like dissolves like” — polar with polar, non-polar with non-polar.
-
Solubility affects real village life — from tea and soap to mining and medicine.
✏️ Practice Quiz
1️⃣ Define solubility.
2️⃣ Explain the effect of temperature on solubility.
3️⃣ Why does oil not dissolve in water?
4️⃣ Give two examples of solubility in daily life.
5️⃣ Describe one village activity that depends on solubility.
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