Experiment 1: General Apparatus, Laboratory Techniques, and Paper Chromatography Notes

General Apparatus and Lab Safety

Objectives
- The students will be able to identify the appropriate apparatus to measure volume, mass, temperature, and time of reactions.
- The students will be able to indicate the suitable apparatus for a variety of simple experiments
- The students will be able to use a various kinds of apparatus based on guidance’s of work safety in chemistry laboratory.
Apparatus
- A variety of apparatus in the chemistry laboratory
Materials
- Water
- Salt
Task 1: List all the apparatus for:
- grinding solid.
- into powder.
- measuring time.
- measuring approximate volume.
- measuring exact (precise) volume.
- measuring mass.
- measuring temperature.
- transfer small quantities of liquid.
- heating the substances.
- filtering the substances.
Data to be recorded
- Record all your finding into the data below.
- Result Apparatus
- To grind solid into powder
- To measure time
- To measure approximate volume
- To measure exact (precise) volume
- To measure mass
- To measure temperature
- To transfer small quantities of liquid
- To heat the substances
- To filter the substances

Laboratory Techniques

Objectives
- The students will be able to use a proper technique when do the experiments.
Apparatus
- A variety of apparatus in the chemistry laboratory
Materials
- Water
- Salt
Task 2: Measure Volume
- Measure the volume of about $50 \,\mathrm{cm^3}$ of aquadest.
- Measure exactly the volume of $25.0 \,\mathrm{cm^3}$ of aquadest.
- Measure exactly the volume of $10.0 \,\mathrm{cm^3}$ of aquadest.
- Measure exactly the volume of $7.0 \,\mathrm{cm^3}$ of aquadest.
Task 3: Measure Mass and Temperature
- Weigh $1 \text{ g}$ of salt.
- Grind the salt into the fine powder, then dissolve the salt in $50 \,\mathrm{cm^3}$ of aquadest.
- After the salt is completely dissolved, heat it until the temperature increase $2^{\circ}\text{C}$ .
- Record the temperature before and after the heating.
Task 4: Crystallization and Filtration
- From task 3, filter the salt solution.
- Evaporate the salt solution.
- Put on the ice cube and observe to forming unsaturated solution.
- Dry the salt after filtration.
Results (to be filled during experiment)
- Apparatus to prepare: - Measure mass and temperature
- Temperature Before
- Temperature After
- Crystallization and Filtration
- Mass Before Filtration
- Mass After Filtration

PAPER CHROMATOGRAPHY

Objectives

The students will be able to identify paper chromatography using ink/food colouring.

Apparatus

Ruler
Pencil
Beaker glass
Spatula
Tape

Materials

Rubbing alcohol
Ink

Procedures

Preparing chromatography paper:
- Cut the paper towel: $2\text{ cm} \times 15\text{ cm}.$ Then, measure $4\text{ cm}$ from one end and draw a line using a pencil and a midline dividing the 4 cm line you just drew (as shown in the picture below). This is the baseline. It’s important to use pencil because lead will not dissolve in water, preventing experimental error in chemical separation.
Using black ink pen or marker, draw a small dot at the cross section of two lines you have drawn previously.
Pour the solvent in the beaker glass.
Place the chromatography paper inside the cup and make sure that the solvent does not reach where the ink is. Also, make sure that the chromatography paper doesn’t touch the bottom of the cup. Tape the other end of chromatography paper to a pencil and place it on the cup.
Wait for about 15 minutes. Then, take out the chromatography paper.
Using the same set up, repeat the experiment with different types of black ink pen/marker.

Results and Analysis

Results Summary

Result A : B : Rf : Analysis
Note: This section records the observable results per ink type, including the separation pattern and the calculated Rf value.

Guided Questions

What is the definition of Rf value? …………………………………………………………………………………………………… ……………………………………………. …………………………………………………………………………………………………… ……………………………………………. ………………………………………………………… …………………………………………….
What can be explained in the Rf value? …………………………………………………………………………………………………… ……………………………………………. …………………………………………………………………………………………………… ……………………………………………. ………………………………………………………… …………………………………………….
What can we learn about the particle when the Rf value is shown? …………………………………………………………………………………………………… ……………………………………………. …………………………………………………………………………………………………… ……………………………………………. ………………………………………………………… …………………………………………….

Additional Notes and Explanations

What is the Rf value? The Rf value is a ratio that describes how far a substance travels in a given solvent system relative to the solvent front.
- Definition (formal): $Rf = \frac{d<em>{\text{solute}}}{d</em>{\text{solvent}}}$ where
- $d_{\text{solute}}$ is the distance moved by the solute (spot) from the baseline,
- $d_{\text{solvent}}$ is the distance moved by the solvent front from the baseline.
- The Rf value is dimensionless and typically falls between 0 and 1: $0 \le Rf \le 1$ .
- The Rf depends on the interaction of the solute with the stationary phase (paper) and the mobile phase (solvent). A more polar solute or a solvent that strongly interacts with the solute will have different Rf values compared to less polar conditions.
Practical interpretation:
- A higher Rf value means the solute traveled farther toward the solvent front.
- Identical Rf values under the same conditions suggest components with similar polarity/affinity in that system, useful for identifying components.
Connections to foundational principles:
- Chromatography relies on differential partitioning between a stationary phase and a mobile phase.
- The choice of solvent, paper (cellulose with its own polarity), and ambient conditions influence separation quality and Rf values.
Hypothetical scenario:
- If you use two inks with the same polarity but different trace components, they may separate into distinct spots with different Rf values, revealing multiple components within a single ink sample.
Ethical and practical implications:
- Accurate measurement and safe lab practices are required when handling solvents like rubbing alcohol.
- Documentation of observations and repeatability are essential for valid conclusions.