This laboratory session delves into the concept of solubility, examining how various solutes—such as table salt, sugar, chalk powder, sodium bicarbonate, and cornstarch—dissolve in water and, potentially, in ethanol or oil at varying temperatures. The aim is to uncover the effect of temperature on the solubility of different substances in each solvent, thereby understanding the dynamic relationship between temperature, solute, and solvent in the dissolution process.
Educational Goals
- Understanding Solubility: Participants will explore the fundamental concept of solubility, learning how a solvent’s capacity to dissolve a solute is influenced by temperature and the chemical nature of both the solute and the solvent.
- Temperature’s Impact on Solubility: The session aims to demonstrate that the solubility of most solids in water increases with temperature, facilitating a greater dissolution of the solute.
- Chemical Interaction Insights: Through the comparison of different solutes’ solubility in various solvents, participants will gain insights into the significance of chemical interactions in dissolution processes.
This session not only illuminates the basics of solubility but also offers an invaluable hands-on experience. By investigating the solubility of various substances under different conditions, participants will achieve a comprehensive understanding of how temperature and chemical properties influence solubility. This exploration underscores the importance of chemical interactions in solubility, offering a practical application of chemistry principles essential for studies and research in the field.
Protocol
Water measurement
a) Use a graduated cylinder to measure 100 mL of cold water and pour it into a 100 mL beaker.
Preparation for heating
a) Place a magnetic stir bar in the beaker. Position the beaker on the heating plate without turning it on.
Thermometer installation
a) Secure a thermometer in the beaker without it touching the bottom, using a universal clamp and stand.
Weighing salt
a) Using a spatula, add 10 g of table salt to the weighing boat and verify the weight.
b) Pour the salt into the cold water in the beaker.
Salt dissolution
a) Turn on the magnetic stirrer to mix well.
b) Add successive 10 g portions of salt until reaching a total mass of 30 g, waiting each time for complete dissolution.
c) Continue adding 2 g of salt at a time until the salt no longer dissolves and starts to accumulate at the bottom of the beaker.
Heating
a) Turn on the heating plate and set it to 75°C to heat the solution.
b) Observe if the accumulated salt dissolves as the temperature increases.
Replicating the experiment
a) Repeat the same steps with sugar, chalk powder, baking soda, and cornstarch to compare the solubility of these substances. Also, explore using ethanol as alternative solvent.
b) Properly empty the contents of the glassware into the recovery bin and clean with distilled water between experiments.
Anticipated Outcomes
Solubility of table salt as a function of temperature
The results indicate an increase in the solubility of table salt with the rise in temperature. Initially, all the added salt dissolved in water at room temperature (solubility is 36g/100mL), but when more salt was added beyond a certain point, it started to settle at the bottom, indicating the solubility limit had been reached. Upon heating, the solubility increased, allowing more salt to dissolve.
Solubility of different substances in water
Table salt: dissolves in water (36g/100mL at 25C).
Sugar: dissolves in water (91g/100mL at 25C).
Chalk powder: insoluble and settles at the bottom over time.
Sodium bicarbonate: dissolves in water (9.6g/100mL at 25C).
Corn starch: insoluble and settles at the bottom over time.
Solubility in different solvents
In alcohol and oil, all the above substances are insoluble.
Observation of solubility factors
Students will observe how the nature of the solute, the solvent, and temperature affect solubility. For example, they will see that salt dissolves in water but not in oil or alcohol.
Solubility with temperature changes
They will experimentally determine how the solubility of table salt changes with temperature, noting that solubility increases as the temperature rises.
Understanding solubility
Students learn that not all solutes dissolve in all solvents and that the solubility of a substance depends on the chemical nature of both the solute and the solvent.
Effect of temperature
The experiment demonstrates that temperature can significantly influence the solubility of a substance, with higher temperatures generally increasing the solubility of solids in liquids.
Solubility concepts
The experiment illustrates the concept of solubility, showing that it is a property of a substance that can vary depending on the solvent and conditions like temperature.
Nature of Solutes and Solvents
Students observe firsthand that the chemical nature of solutes and solvents determines solubility, highlighting the concept of “like dissolves like” in chemistry. Temperature’s effect on solubility: The experiment provides a practical understanding of how temperature influences the solubility of substances, aligning with the principle that solubility for most solids increases with temperature.
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Basic introduction to solubility and simple observations.
- Activities: Observing how different solutes dissolve in water, simple comparisons of solubility at different temperatures, basic safety instructions.
Grades 6-8 (Ages 11-13)
- Focus: Intermediate understanding of solubility and the effect of temperature.
- Activities: Measuring solubility of various solutes in water and other solvents, observing the impact of temperature on solubility, recording observations, following detailed safety protocols.
Grades 9-12 (Ages 14-18)
- Focus: Advanced understanding of solubility, temperature effects, and chemical interactions.
- Activities: Conducting detailed experiments to measure solubility of different solutes in water, ethanol, and oil at various temperatures, analyzing the chemical interactions affecting solubility, meticulous documentation and analysis of results, adhering to advanced safety protocols.
Laboratory essentials
Instruments
Beakers (50ml, 100ml, 500ml & 1000ml)
Electronic Scale
Graduated Cylinders (70ml & 100ml)
Hot plate
Lab Stand & Clamps
Magnetic stirrer
Spatulas
Test Tubes
Thermometers
Timer
Products
Baking soda (powder)
Calcium carbonate (powder)
Ethanol
Glucose (powder)
Olive oil
Sodium chloride (powder).
Starch (powder).