Classifying information involves both observation and critical thinking. To classify objects into specific groups, you must compare and contrast the similarities and differences among them. Start the activity by showing the children two groups of objects that you have already sorted.

Ask them to determine how the items were sorted and then label each group. Depending on the age of your students, you should sort the objects by a feature that is less obvious than just color or shape. Then have the students see how many different ways they can sort the same objects. Be open to new possibilities. I’m always amazed at kids’ ability to find new ways that I hadn't considered to look at things.

Classifying Mollusks
Have your child sort a group of seashells. Start by sorting the shells into two groups. Then sort the two groups again based on a different feature. Look for differences in the shells. Are some smooth and some rough? Do some shells have ridges? Continue sorting into more and more refined subsets. Label each group according to the feature used to separate them, e.g., size, shape, etc.

Try the mollusk sorting activity that we have included. This is simply sorting by one feature. You can also use the pictures alone for sorting. Think about other ways to classify these animals. For example, you can separate them into two groups by the number of limbs they have. You could also sort them by whether or not each animal has a shell.

Keep sorting each group into more refined subsets. For example, if you sorted the animals by whether or not each one had a shell, you can now separate them into groups based on how many shells each one has. A snail has one shell; a clam has two shells. See how far you can go in refining the groups you make. Are there differences in the shells themselves?

Recording Information
There are different ways to record the results of your sorting. You can start with a simple table, such as the one that goes with the mollusk pictures. A hierarchy diagram, like the one below, works well for showing subsets.

An overlapping Venn diagram can also be used, which lets you show both the common features the objects share in the overlapping area and the unique features in the outer parts of each circle.