Watch the video Growth of Plants in Slow Motion on YouTube. After the video, discuss how the plants are very small in the beginning, then slowly grow bigger and bigger.
Ask the students to act out a plant growing. Allow them to start as seeds (curled up on the floor), then slowly rise and spread out their arms. Ensure that the ‘seeds’ start close together so they run out of space as they grow.
Afterwards, discuss why everyone fit together when they were seeds, but not when they were full-grown plants (the seeds took up less space than the plants). Introduce the term 'volume' and its definition (the space a solid object occupies).

Choose two objects from around the classroom. Ask the students which one they think has the bigger volume (that is, the object which takes up more space). Encourage the class how explain how they can tell. Guide them towards looking at the object’s height, width and depth. Using these parameters, discuss and decide which object has the greater volume.
Write a comparative sentence on the board for the two objects’ volumes e.g. The volume of the soccer ball is larger than the volume of the pencil.

Individually, or in small groups, allow the students to collect five different objects from around the classroom and take them back to their desks. Ask the students to pick one object as their favorite.
Encourage the students to compare the volumes of the objects, then arrange them in order from the smallest volume to the largest. Ask the students to write/draw the list into their workbooks. If the students are having trouble discerning a difference between two objects, ask them to replace one of the objects with something bigger/smaller so they can make an ordered list.
Ask the students to look at their favorite object in the list and encourage them to identify an object that has a larger volume than their favorite. If their favorite object is the largest item in the list, ask the student to identify/think of something else that would have a greater volume.
On the board, model how to write a comparative sentence e.g. The block has a smaller volume than the ball. Allow the students to write their own comparative sentence for their favorite object in their workbook. Repeat the comparative writing process, this time for an object that has a smaller than the student's favorite object.

Ask the students to share their comparisons with three other people. Encourage them to describe how they could tell the difference between volumes.