MYP Chemistry Solutions, Colloids and Suspensions Notes

How Do Solutions, Colloids and Suspensions Differ?

1. Consider mixing salt in water versus sand in water:
   1. Saltwater looks clear and uniform.
   2. Sand in water looks cloudy, and the sand settles at the bottom.
2. These differences come from particle size, visibility, and stability of the mixture.
3. Chemists classify such mixtures as solutions, colloids, or suspensions.

Key Idea: Particle Size and Stability

1. Solutions → very small particles (ions or molecules), fully dissolved.
2. Colloids → medium-sized particles, dispersed but not dissolved.
3. Suspensions → large particles, which can be seen and will settle.

Summary Table - Key Differences Between Solutions, Colloids, and Suspensions

Solutions – True Homogeneous Mixtures

1. Solute → the substance being dissolved (usually in smaller amount).
2. Solvent → the substance doing the dissolving (usually in larger amount).

Key Characteristics of Solutions

1. Particle size: < 1 nm (molecules or ions).
2. Visibility: Individual particles cannot be seen, even with a light microscope.
3. Uniformity: Completely uniform throughout – no lumps, layers, or floating bits.
4. Stability: The solute never settles out on standing.
5. Light scattering: Does not scatter light → no visible beam.

Colloids – In Between Solutions and Suspensions

Colloids are:

1. Heterogeneous at the microscopic level (non-uniform if you zoom in),
2. But appear uniform to the naked eye.
3. Particle size: approximately 1–1000 nm.

Key Characteristics of Colloids

1. Visibility: Particles are too small to see individually with the naked eye, but can be seen with a microscope.
2. Stability: Particles do not settle out under normal conditions.
3. Filtration: Colloidal particles pass through ordinary filter paper.
4. Tyndall effect: Colloids scatter light, making a flashlight beam visible as it passes through.