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
Use a graduated cylinder to measure 100 mL of cold tap water and pour it into a 100 mL beaker.
- Preparation for heating
a) Place a magnetic stir bar in the beaker.
b) Place the beaker on the hot plate without turning it on.
- Installation of the thermometer
a) Attach a universal clamp to the support above the center of the beaker.
b) Place the thermometer in the beaker by securing it with a universal clamp without it touching the bottom.
- Weighing of salt
a) Using a spatula, add approximately 10 g of table salt (sodium chloride) into the pan.
b) Pour the salt into the cold water of the beaker.
- Dissolution of salt
a) Activate the magnetic stirrer to mix well.
b) Add successively 10 g portions of salt up to an additional total of 20 g, waiting each time for complete dissolution.
c) Continue to add 2 g of salt at a time until the salt no longer dissolves and begins to accumulate at the bottom of the beaker.
Note the total amount of salt that was poured into the beaker to reach this point where the salt no longer dissolves and begins to accumulate at the bottom of the beaker.
- Heating
a) Set the hot plate to 75°C to heat the solution.
b) Observe whether the accumulated salt dissolves with the increase in temperature.
c) Note the temperature displayed on the thermometer at the moment when the salt becomes completely dissolved.
- Reproduction of the experiment
a) Repeat the same steps with the sugar (glucose), the chalk powder (calcium carbonate), the sodium bicarbonate, and the corn starch (starch) to compare the solubility of these substances.
b) Thoroughly empty the contents of the glassware into the recovery container and clean with distilled water between experiments.
c) For each solid, the quantity you will have to add to the beaker of water to obtain complete dissolution will vary from one solid to another.
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)