The density of a suspension is calculated by dividing the total mass of the particles and the liquid (usually water) by the total volume of the suspension.
Understanding Suspension Density
The key to determining suspension density lies in understanding that it is a combined property of both the solid particles and the liquid in which they are suspended. The reference defines the density of a suspension as:
The density of a suspension of particles is equal to the mass of the particles and water divided by the suspension volume.
This means we need to consider both the mass and the combined volume when calculating density.
Calculating Suspension Density: Step-by-Step
Here's a breakdown of how to find density using the suspension method:
- Determine the Mass of Particles: This can be tricky depending on the particles. However, the reference mentions that we can focus on the concentration of the core particles in the case of flocs and ignore the flocs' diameter.
- Determine the Mass of the Liquid (e.g., Water):
- Measure the volume of the liquid used.
- Use the known density of the liquid to calculate the liquid’s mass.
- For water, this is approximately 1 gram per milliliter or 1 gram per cubic centimeter.
- Determine the total mass: Add the mass of particles (Step 1) and liquid (Step 2). This gives you the total mass of the suspension
- Measure the total volume of the suspension. This measurement includes both the particles and the liquid.
- Calculate the density: Use the formula:
Density = (Total Mass of Particles + Liquid) / Total Volume of Suspension
Practical Considerations and Insights
- Flocs: When dealing with flocs (aggregates of particles), the focus is on the core particles. The reference suggests ignoring the floc diameter for density calculation.
- Measurement Accuracy: Accurate measurements of mass and volume are essential for an accurate density value.
- Settling: If the particles settle, the suspension is no longer homogeneous, and density calculation can become more complex. It is best to take measurements when the suspension is well-mixed.
Example
Let's say we have:
- 10 grams of particles
- 100 ml of water
- Total suspension volume of 108 ml.
- Mass of the particles = 10 g
- Mass of water = 100 ml * 1 g/ml = 100 g
- Total Mass = 10 g + 100 g = 110g
- Total suspension volume = 108 ml
- Density = 110g / 108 ml = 1.019 g/ml (approximately)
| Parameter | Value |
|---|---|
| Mass of Particles | 10 g |
| Mass of Water | 100 g |
| Total Mass | 110 g |
| Total Volume | 108 mL |
| Density | 1.019 g/mL |
