Angle of Repose
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required
Categories: Materials, Measurement and Units
Alternative titles: Determining the Flow Properties of Powders
Summary
This experiment determines the flow characteristics of powders by measuring the angle of repose—the steepest angle at which a material can rest without sliding. Sand samples of different particle sizes and moisture contents are poured to form heaps, and the angle of each heap is measured to evaluate how size, shape, and cohesion affect powder flowability.
Procedure
Prepare several samples of sand with different particle sizes or mixtures.
Place each sample in a cylinder or container with a removable base.
Lift the cylinder vertically, allowing the sand to flow freely and form a heap on a flat surface.
Measure the height and base diameter of the heap using a ruler.
Calculate the angle of repose using the formula:
θ = tan⁻¹(height / radius)
Repeat the process for each sand type, including one with added moisture or glidant.
Record all measurements and compare the calculated angles to assess flow properties.
Links
Angle of Repose | Determination of Angle of Repose With Calculation | Angle of Repose - Solution- Pharmacy:
ANGLE OF REPOSE | HOW TO PERFORM IN LABORATORY? DETAIL CALCULATION | IMPORTANCE OF FLOW PROPERTY - PHARMAROCKS THE WAY OF SUCCESS:
📄 Angle of Repose - Pharmaceutical Technology: https://pharmatechno2014.blogspot.com/p/d-angle-of-repose.html
Variations
Repeat the experiment using different powders.
Compare dry and slightly damp samples to examine the effect of moisture.
Use mechanical methods such as a tilting box or revolving cylinder to measure dynamic angles of repose.
Safety Precautions
Work on a clean, stable surface to prevent spills or contamination.
Handle glassware and measuring tools carefully.
Questions to Consider
Which sand sample had the lowest angle of repose, and what does that indicate? (A lower angle indicates better flowability.)
How does particle size affect flow characteristics? (Smaller particles increase cohesion, leading to higher angles of repose.)
What is the effect of adding moisture or glidant? (Moisture increases cohesion and the angle of repose, while glidants reduce it.)
How does particle shape influence the results? (Round particles roll more easily and form lower angles than irregular ones.)
What alternative methods can be used to measure angle of repose? (Tilting box, fixed funnel, or revolving cylinder methods.)