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๐ฌ Think about it
Sugar dissolves faster and more in hot milk than in cold milk. Heating the solvent seems to give it more room for solute. So does temperature change how much can dissolve? Let's heat things up and watch.
Does heating help a solvent dissolve more solute?
- Undissolved baking soda dissolves when the water is heated.
- Water at 70°C dissolves more than water at 50°C.
- Water at 20°C dissolves even less.
- For most substances, solubility increases with temperature.
More Heat, More Solute Dissolves
Water at 20°C
Dissolves the least baking soda.
↓
Heat to 50°C
More baking soda dissolves.
↓
At 70°C: dissolves the most
In this Activity, we will heat a saturated baking soda solution to show that heating dissolves more solute.
Safety first
Be careful while using the heating device.
Materials needed
About 50 mL water, a glass beaker, a laboratory thermometer, baking soda (sodium hydrogen carbonate), a spirit lamp, a stirrer, a tripod stand.
Procedure
1. Take about 50 mL of water in a beaker and measure its temperature, say 20°C.
2. Add baking soda and stir, continuing till some baking soda stays undissolved.
3. Heat the contents to 50°C while stirring and observe the undissolved baking soda.
4. Add more baking soda while stirring until some stays undissolved again.
5. Heat further to 70°C while stirring and observe.
2. Add baking soda and stir, continuing till some baking soda stays undissolved.
3. Heat the contents to 50°C while stirring and observe the undissolved baking soda.
4. Add more baking soda while stirring until some stays undissolved again.
5. Heat further to 70°C while stirring and observe.
Observation
The undissolved baking soda dissolves each time the temperature is raised. Water at 70°C dissolves more than at 50°C, which dissolves more than at 20°C.
Explanation
For most substances, solubility increases with temperature. A saturated solution at one temperature behaves as an unsaturated solution if the temperature is increased, so it can dissolve more solute.
โ Summary
- Saturated soda solution made
- Heated step by step
- More dissolves each time
- Solubility rises with heat
๐ Our scientific heritage
- Water has long been used as a solvent in Ayurveda and Siddha.
- Drug formulations also used hydro-alcoholic herb extracts.
- Oils, ghee, milk, and other substances were used as solvents.
- This helped achieve the medicine's therapeutic benefits.
๐ฌ Be a scientist
- Asima Chatterjee developed anti-epileptic and anti-malarial drugs.
- She used solvents and solutions to extract plant compounds.
- She was the second Indian woman to earn a Doctorate of Science.
- She won the Shanti Swarup Bhatnagar Award and the Padma Bhushan.
Important Points
- For most solids, solubility increases with temperature.
- Heating a saturated solution makes it unsaturated again.
- Water at 70°C dissolves more baking soda than at 20°C.
Important Definitions
- Effect of temperature on solubility — for most solids, the amount that dissolves increases as the temperature rises.
