This tutorial is designed to teach students two fundamental techniques of separation and purification in chemistry: decantation and filtration. Through hands-on experience, students will learn to separate a solid from a liquid in a heterogeneous mixture, gaining practical skills and understanding the underlying principles of solubility and physical properties.
Educational Goals
The purpose of this experience is to put into practice two fundamental techniques of separation and purification in chemistry: decantation and filtration.
Part 1: Decantation
- The decantation aims to separate the phases from a heterogeneous mixture composed of an unparalleled solid (in this case, cobalt hydroxide (II)) and a liquid (water), by exploiting their difference in density. The objective is to obtain a clearer liquid by gently pouring the upper aqueous phase into another container, leaving behind the solid deposited at the bottom of the first beaker. This step allows a coarse separation of the solid and liquid, in preparation for a finer purification.
Part 2: filtration
- The filtration is used to complete the separation started by the decantation, by removing the residual solid particles which were transferred with the liquid in the second Becher.
- This process uses a filter placed in a funnel to separate the solid (residue) and liquid (filtrate) phases from the mixture.
- The filtrate, which is the liquid having crossed the filter, should be purer than the initial mixture, while the residue, made up of solid particles, remains on the filter. By combining decantation and filtration, this experience aims to teach how to perform an effective separation of the components of a heterogeneous mixture, to understand the principle of solubility and the physical properties which allow the separation of phases, as well as to familiarize the participants with the ‘Use of standard laboratory equipment for the separation of mixtures.
Protocol
The purpose of this laboratory is to separate the constituents of a mixture of cobalt (II) hydroxide and water.
Part 1: Decantation
This method allows for preliminary separation, as cobalt (II) hydroxide is not soluble in water.
1. An aqueous solution with a deposit of cobalt (II) hydroxide has been resting for at least 5 minutes.
2. Gently pour the liquid part (water) of the mixture into a second beaker.
a) At this stage, solid particles may end up in the second beaker.
3. Let the first beaker rest on the counter for the remainder of the laboratory. The residual water will be able to evaporate.
Part 2: Filtration
This method allows for the removal of solid particles that end up in the mixture after decantation.
1. Attach a medium clamp to the universal stand on the right.
2. Insert the filter into a funnel.
3. Attach the funnel to the clamp on the universal stand.
4. Place an Erlenmeyer flask under the funnel’s opening.
5. Slowly pour the mixture over the thick part of the filter.
6. Allow the mixture to pass through the filter.
a) The liquid obtained is called the filtrate.
b) The solid part remaining in the filter is the residue.
Anticipated Outcomes
The objective of this laboratory exercise is to separate the constituents of a mixture of cobalt (II) hydroxide and water. The process involves two main separation techniques: decantation and filtration, which are fundamental in separating solid and liquid phases in a mixture.
Part 1: Decantation
Decantation leverages the insolubility of cobalt (II) hydroxide in water. After allowing the mixture to settle, the water, which is the supernatant liquid, is gently poured off into another beaker, leaving the solid cobalt (II) hydroxide behind. This step is crucial as it relies on the difference in density between the solid and liquid to achieve separation. Some solid particles might transfer into the second beaker, which necessitates the next step, filtration.
Part 2: Filtration
Filtration is employed to remove any remaining solid particles that were inadvertently transferred with the water during decantation. The mixture is poured through a filter, which captures the solid particles, allowing only the liquid to pass through. The liquid collected at this stage is called the filtrate, and the solid retained on the filter is the residue.
During the decantation, the primary outcome is the partial separation of cobalt (II) hydroxide from the water. This step is significant because it demonstrates the principle of using physical properties (solubility and density) for separation.
During the filtration, the expected outcome is the complete separation of the solid cobalt (II) hydroxide from the water. This step is essential to ensure that any solid particles that escaped during decantation are captured, illustrating the efficacy of filtration in separating solids from liquids based on particle size. The significance of these procedures lies in their wide applicability in various scientific fields, including chemistry, environmental science, and engineering. Understanding these fundamental separation techniques is crucial for students as they are integral to many laboratory and industrial processes, from purifying chemicals to treating wastewater. This lab not only helps in understanding the specific properties of cobalt (II) hydroxide and water but also reinforces the concept of phase separation and the practical applications of decantation and filtration in real-world scenarios.
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Basic introduction to separation techniques and simple observations.
- Activities: Observing decantation and simple filtration, basic safety instructions.
Grades 6-8 (Ages 11-13)
- Focus: Intermediate understanding and application of separation techniques.
- Activities: Performing decantation and filtration, understanding chemical purity, detailed safety protocols.
Laboratory essentials
Instruments
Beaker (50ml & 1000ml)
Erlenmeyer (250 ml)
Funnel
Funnel filter
Glass rod
Graduated cylinder (70ml)
Hot plate
Lab Stand & Clamps
Magnetic stirrer
Plastic connector
Test tubes
Thermometers
Timer
Products
Cobalt hydroxide (II)