Set out two glasses of the same volume that are different shapes. Fill both with water. Ask the students which glass contains more water. Record their responses.
Empty one of the glasses. Ask the students whether the glass that you just emptied will be partially full, full or overflowing if you pour the water from the other glass into it. Record their responses.
Pour the contents of the full glass into the empty glass. Ask the students which glass can hold more water after they have seen the demonstration. Tell them that the glasses hold the same volume even though they have different shapes.
Set out a glass that holds a larger volume of water. Ask the students whether they think the new glass will be partially full, full or overflowing if you pour the water from the other glass into it. Record their responses.
Pour the water from the smaller glass to the larger glass. Talk about capacity with the students. Discuss why they think the larger glass is not full after receiving the contents of the smaller glass.
Demonstrate the idea of capacity. Refill the smaller glass and pour it into the larger glass. Repeat the process until the larger glass is full and record the number of smaller glasses that fit into the larger glass.