How to use water displacement to measure volume

When you want to try and measure the volume of an irregularly shaped object, it is often difficult and complicated to do. The easiest method to achieve this is known as the "water displacement method". This is the most commonly used technique and is very simple and accurate. The steps for the water displacement method are listed below.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• irregularly shaped object - such as a stone
• Glass/plastic meauring cup or measuring beaker large enough to accomodate your object.

1. Write down the following equation on a piece of paper:
   
   [(b) - (a)] = Volume of odd shaped object

2. Find a graduated cylinder that will be large enough to fit the object being measured into.

3. Fill the graduated cylinder enough so that when placed in the graduated cylinder, the object will be fully submerged in the water. Also be careful not to put in so much water that the water level will rise past the graduated cylinder's markings when the object is placed in the graduated cylinder.

4. After filling the graduated cylinder to a level that will allow us to put our object in without spilling, record the volume of the water as (a) in your equation that we wrote down in Step 1. Make sure to read the meniscus when determining volume.

5. After the water' s volume has been recorded, carefully place the object in the graduated cylinder and record this volume as (b) in your equation that we wrote down in Step 1.

6. Now we want to calculate the volume of the irregularly shaped object that we placed in the graduated cyclinder. To to this, subtract the volume of the water alone from the volume of the water and object using the equation that we wrote down in Step 1: [(b) - (a)] = Volume of odd shaped object.

Tips & Warnings

• If the object is not fully submerged in the water, the recorded volume of the object will be invalid.
• If the water raises above the measuring markings of your container, an accurate reading cannot be made, and you need a bigger container.
• Measure the mass of the object before placing it in the water, and then again after placing it in the water to see if the water absorbed into the object and is changing the volume of your object.
• Use the smallest possible container that is sufficient for measuring the object.
• The object being measured should not be dropped into the container, but allowed to gently float to the bottom. This way you will not splash water onto the side of the container and mess up your measurement.
• If you are using a porous object, it is best to seal it before putting it into the water to avoid extra water weight.