Sorting Solids and Liquids by Their Properties
Students observe, describe, and sort solids and liquids based on properties such as shape, texture, color, and how they behave in a container.
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What Are Solids and Liquids?
Matter is anything that takes up space. Solids and liquids are two kinds of matter. A solid keeps its own shape when you move it. A wooden block stays block-shaped whether it is on a table or in a box. A liquid can flow and take the shape of its container. Water may look tall in a narrow cup and low and wide in a bowl. The water is still the same liquid even though its shape changes. Solids and liquids can have different colors, textures, and other observable properties. You can use these properties to describe and classify materials. Look carefully at each sample and ask, “Does it keep its shape, or does it flow and take the shape of its container?”
Observe Safe Classroom Samples
Scientists plan safe ways to observe materials. Your teacher may provide samples such as a plastic cube, a cotton ball, a metal spoon, water, cooking oil, and liquid soap. Keep every sample in its assigned tray or container. Use your eyes to notice color, shape, and shine. With permission, gently touch solid samples to notice whether they feel rough, smooth, hard, or soft. Do not taste any sample, and do not put materials near your eyes or mouth. Read picture cards or container labels to learn what each sample is. These are helpful sources of information. For example, you can observe that oil flows, and a label can confirm that the sample is cooking oil. Ask your teacher if you are unsure how to examine something safely.
Describe Observable Properties
An observable property is something you can notice with your senses or through a simple test. For solids, describe color, shape, texture, hardness, and flexibility. A red rubber eraser is solid, smooth, and flexible. A gray metal spoon is solid, smooth, hard, and shiny. For liquids, notice color, clarity, and how they flow. Water is clear and flows quickly. Liquid soap may be colored and flow more slowly. Use exact describing words instead of saying only “nice” or “weird.” You can compare two samples by saying, “The cotton ball is softer than the wooden block.” Never taste a material to identify it. Careful property words help other people understand what you observed and give you evidence for sorting the samples.
Sort and Classify the Samples
To classify means to place things into groups based on a shared property. First, choose a sorting rule. You might sort samples into solids and liquids. Test each sample: Does it keep its own shape, or does it flow and take the shape of its container? A wooden block and a cotton ball belong in the solid group because each keeps its shape. Water and cooking oil belong in the liquid group because they flow. You can also sort the solids by texture, such as rough or smooth, or sort liquids by color, such as clear or colored. One sample may fit more than one description. For example, a plastic button can be solid, smooth, hard, and blue. Always tell which observable property you used so another person can repeat your sort.
Record Evidence
Scientists record what they observe so they can answer questions with evidence. Make a table with one row for each sample. Write or draw the sample name, whether it is a solid or liquid, and two or more observable properties. For a wooden block, you might record: solid, brown, hard, and rough. For water, you might record: liquid, clear, and flows quickly. Record only what you actually observe or learn from a trusted source, such as the sample label, a classroom book, or your teacher. Then use the table to answer a question. If the question is “Which samples flow?” look down the table for evidence about flowing. Your notes help you remember the investigation and explain why each sample belongs in a group.
Share a Classification Rule
After sorting, explain your classification rule to a partner or the class. A useful rule names the property used and tells how samples were placed into groups. You might say, “I put materials that keep their own shape in the solid group. I put materials that flow and take the container’s shape in the liquid group.” Point to observations in your table as evidence. Then invite someone to test your rule with another sample. If liquid soap flows into a cup’s shape, your rule places it with the liquids. Listen to other rules, too. A classmate might sort solids into rough and smooth groups instead. Both sorts can be useful when the rule is clear and based on observable properties. Revise your explanation if a sample does not fit the rule.
