Finding the volume of a regular object, such as a cube or sphere, is usually done using a formula. Irregular objects such as screws or stones require a more practical approach. Fortunately, there is a direct way to calculate the volume of an irregular object using observations of the water level in a measuring cylinder.
Step
Part 1 of 3: Reading the Initial Water Level
Step 1. Put water into the measuring cylinder
Choose a measuring cylinder that fits the object to be inserted. Tilt the cylinder when pouring water to minimize bubbles. Pour enough water to fill half the cylinder.
Step 2. Read the point of the meniscus
Notice that the water level on the cylinder wall is higher and slightly lower in the middle. This drop is called the meniscus and is the reference point for measuring the water level. Make sure the cylinder is on a flat surface and there are no bubbles in it. Pay close attention to where the meniscus is.
Step 3. Record the measurement results
Knowing the exact water level is very important. Write down the measurement results in a table or notebook. The measurement results use the unit mL.
Part 2 of 3: Measuring the Final Water Level
Step 1. Insert objects
Tilt the cylinder. Gently dip the object into the water. Make sure the object is completely submerged in the water. If the water is not enough to submerge the object, add more water to the cylinder.
Step 2. Take the measurement again
Let objects and water settle down. Make sure the cylinder is on a flat surface. Now look at the water level (again read the meniscus point). The water level should increase due to the addition of objects into the cylinder.
Step 3. Record the final measurement results
The final measurement is as important as the initial measurement in the calculation. This measurement must also be precise. Write the final water level in mL in a table or notebook.
Part 3 of 3: Calculating the Volume of Objects
Step 1. Understand how to measure
Some will immediately conclude that the final reading is the volume of the object, but this is not true. The final reading is the volume of water plus the volume of the object. We need to find the difference between the final and initial readings to find the volume of an object.
Step 2. Find the difference between the initial and final heights
Use the formula Vtotal - Vwater = Vobject. Vtotal is the final measurement, Vwater is the initial measurement, and Vobject is the volume of the object. In other words, subtract the second measurement from the first to find the volume of the object.
Step 3. Analyze your answers
Make sure the resulting volume is reasonable. Check your calculations with a calculator. Some sure signs of an error are if the volume of the object is negative (this is not possible) or the volume of the object is greater than the capacity of the cylinder (30 mL volume cannot be measured in a 25 mL cylinder). If your answer seems wrong, first check the formula to make sure your calculation is correct. After that, do the experiment again to get a new measurement result.
- If the volume result is negative, you most likely misplaced the start and end measurements in the formula and don't need to repeat the experiment.
- If the measurement results are too large and don't make sense, you must have miscalculated or measured wrong. If the measurement is wrong, you have to repeat the experiment.
Tips
- Make sure you measure the meniscus point correctly.
- Measure several objects and compare.
