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Investigate the Properties of Liquids

Summary

Grade Range
2nd
Group Size
2-3 students
Active Time
1 hour 25 minutes
Total Time
1 hour 25 minutes
Area of Science
Physics
Chemistry
Key Concepts
Properties of Liquids
Credits
Svenja Lohner, PhD, Science Buddies
Two mini cups filled with corn syrup, green water, and vegetable oil and showing the layering of the different liquids.

Overview

When discussing material properties, most of us usually think of solid materials and material properties such as hardness, flexibility, or strength. However, liquids are characterized by distinct properties, too. Some of these properties overlap with those of solids, like density or transparency, but others are more specific to liquids. Viscosity—the resistance of a fluid to flow—and surface tension, are two examples of properties that are specifically used to characterize liquids. In this lesson plan, students will investigate the properties of different liquids by pouring them, smelling them, and investigating their densities by stacking them on top of each other.

Learning Objectives

NGSS Alignment

This lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
This lesson focuses on these aspects of NGSS Three Dimensional Learning:

Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
Science & Engineering Practices Planning and Carrying Out Investigations.
Plan and conduct an investigation collaboratively to produce data to serve as the basis for evidence to answer a question.
Disciplinary Core Ideas PS1.A: Structure and Properties of Matter.
Different kinds of matter exist and many of them can be either solid or liquid, depending on temperature. Matter can be described and classified by its observable properties.
Crosscutting Concepts Patterns.
Patterns in the natural and human designed world can be observed.

Materials

Materials needed for the 'Investigate the Properties of Liquids'  lesson plan.

Materials for each group of 2-3 students:

Materials for teacher:

Background Information for Teachers

This section contains a quick review for teachers of the science and concepts covered in this lesson.

Different materials are characterized by different properties. This is not only true for solids but also for liquids. Liquids and solids share many properties. Among them are, for example, the transmittance, which measures how much light is able to pass through a material, and the density. The density is different for each individual compound and defined as the mass of a compound divided by its volume. In other words, the more matter there is in a certain amount of volume, the denser a substance is. All types of matter—solids, as well as liquids—are made up of many different atoms. Depending on the mass of these atoms, their size, and the way they are arranged, different substances will have different densities. One cubic centimeter (1 cm³) of rock, for example, is much heavier than 1 cm³ of wood. This is because there is much more matter in the same volume of rock compared to the wood. Liquids can also have different densities. Freshwater, for example, has a density of about 1 gram per cubic centimeter (g/cm³) at room temperature. The density of an object will determine whether it sinks or floats in water. Any substance—either liquid or solid—that has a higher density than water will sink, whereas substances with a lower density than that will float (Figure 1).

 Schematic diagram of two beakers filled with water next to each other. The left beaker shows a sunken metal key. The right beaker shows a floating rubber duck.
Figure 1. Objects with a density higher than water will sink (left) and objects with a lower density than water will float (right).

There are also some properties that are used to specifically characterize a liquid. Surface tension or viscosity are two examples. The viscosity of a liquid is a measure of its resistance to deformation or flow. It is also often referred to as the "thickness" of a liquid. The thicker a liquid is, the higher is its velocity. Corn syrup, for example, has a higher viscosity than water. An easy way to measure viscosity is to measure how long it takes for a liquid to pour out of a cup into another container, and how long it takes until it takes the shape of the receiving container. Water will do that almost instantly, whereas corn syrup will take some time to pour out and settle.

Liquids also experience surface tension. The molecules a liquid is made of pull on each other or exert a force. As shown for water in Figure 2, a water molecule in the middle of a droplet gets pulled equally in all directions by the neighboring molecules. However, a molecule at the surface of the droplet gets pulled mostly inward by the molecules below it. This means that all the molecules at the surface help "hold together" the droplet of water, which is called surface tension. The surface tension of different liquids can be determined by measuring how much volume of each liquid fits on a penny before it spills over the edge of the penny.

Diagram shows water molecules in a droplet pulling towards other water molecules
Figure 2. A diagram showing the forces on water molecules that create surface tension. Note that the diagram is not to-scale—there are quintillions of water molecules in a single drop!

In this lesson plan, students will investigate the properties of different liquids. By pouring, smelling, or stacking them on top of each other, they will realize that not all liquids have the same properties. They can vary in color (transmittance), smell, viscosity, or density (mass per volume).

Prep Work (15 minutes)

Engage (20 minutes)

Explore (45 minutes)

Reflect (20 minutes)

Make Career Connections

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