Properties of Water: Polarity and Cohesion

Active learning helps students grasp water’s molecular behavior because hands-on tests make abstract polarity visible. When students see how many drops fit on a penny or how water climbs celery stalks, they connect microscopic charges to real-world phenomena they observe every day.

• Primary 5
• Science
• 4 activities
• 20 min–40 min

Learning Objectives

1. Explain how the uneven sharing of electrons in a water molecule creates partial positive and negative charges.
2. Demonstrate cohesion by observing the behavior of water droplets on a surface.
3. Analyze the role of adhesion in water's ability to move upwards against gravity in narrow tubes.
4. Classify substances as soluble or insoluble in water based on experimental results.
5. Predict how changes in water's properties would affect common biological processes.

Inquiry Circle

⏱ 20 min·Whole Class

Demonstration: Drops on a Penny

Place a penny on a paper towel and add water drops one by one using a dropper, counting until the water overflows the edge. Have students predict the maximum drops before overflow and record observations. Discuss how cohesion allows the dome shape. Clean and repeat with soapy water to compare.

Prepare & details

Explain how the polarity of water molecules leads to its unique properties.

Facilitation Tip: During the Drops on a Penny demonstration, use two pennies side-by-side—one clean and one slightly greased—to show how surface properties change cohesion outcomes.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 40 min·Pairs

Inquiry Circle: Celery Capillary Action

Cut celery stalks and place in colored water glasses. Observe and sketch color rise in leaves over 30 minutes. Pairs measure height every 10 minutes and hypothesize why water moves up against gravity. Connect to adhesion and cohesion in plant transport.

Prepare & details

Analyze the significance of water's cohesive and adhesive properties in biological systems.

Facilitation Tip: In the Celery Capillary Action inquiry, have students measure and record the height of colored water in stalks every 5 minutes to build a time-series graph.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Stations Rotation

⏱ 30 min·Small Groups

Stations Rotation: Solvent Test

Set up stations with salt, sugar, oil in water and oil. Students stir samples, observe dissolution, and test with iodine for starch. Rotate stations, noting polarity's role in solubility. Groups share findings in a class chart.

Prepare & details

Predict how life on Earth would differ if water did not exhibit these unique properties.

Facilitation Tip: At the Solvent Test stations, ask students to rotate in small groups so they can compare how quickly polar and nonpolar substances dissolve or remain separate.

Setup: Tables/desks arranged in 4-6 distinct stations around room

Materials: Station instruction cards, Different materials per station, Rotation timer

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Inquiry Circle

⏱ 25 min·Small Groups

Exploration: Floating Paperclip

Fill a bowl with water. Gently place a paperclip on tissue paper, then sink the tissue to float the clip. Students test with soap-dipped clips and explain surface tension breakage. Draw before-and-after diagrams.

Prepare & details

Explain how the polarity of water molecules leads to its unique properties.

Facilitation Tip: For the Floating Paperclip exploration, demonstrate proper surface tension technique by lowering the paperclip gently with a bent paperclip or forceps to avoid breaking the film.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Teaching This Topic

Teachers should start with concrete, relatable examples before moving to models or diagrams, because water’s polarity is invisible. Avoid jumping straight to abstract diagrams; let students first observe cohesion and adhesion in action, then use those experiences to interpret models. Research shows that when students manipulate materials and record observations, they retain concepts better than when they only listen to explanations or watch videos.

What to Expect

Students will explain cohesion as water sticking to itself and adhesion as water sticking to other materials, using evidence from their tests. They will also predict and test how polarity affects water’s ability to dissolve substances or support objects.

Watch Out for These Misconceptions

Common Misconception

During the Drops on a Penny demonstration, watch for students who claim cohesion and adhesion are the same property when they see water forming beads.

What to Teach Instead

Ask students to compare drops on a clean penny versus a lightly greased one; the greased surface shows reduced adhesion, making beads form instead of spreading, which highlights the difference between cohesion and adhesion.

Common Misconception

During the Solvent Test station rotation, watch for students who assume water dissolves all substances equally without testing.

What to Teach Instead

Have students predict which substances will dissolve before testing, then discuss why oil forms a separate layer while salt disappears, linking polarity to outcomes.

Common Misconception

During the Floating Paperclip exploration, watch for students who think water molecules have full charges like ions.

What to Teach Instead

Use a visual model with labeled bar magnets to show partial charges; place two bar magnets near each other to demonstrate attraction without full charges.

Assessment Ideas

Exit Ticket

After the Drops on a Penny demonstration, provide students with two scenarios: 1) A water strider walking on a pond. 2) Water rising in a narrow straw. Ask them to write one sentence for each scenario explaining which property of water (cohesion or adhesion) is primarily at play and why.

Quick Check

During the Floating Paperclip exploration, show students a collection of small items (e.g., a paperclip, a small leaf, a coin). Ask them to predict whether each item will float on water, then test their predictions. Discuss how surface tension affects the outcome for items that are denser than water.

Discussion Prompt

After the Celery Capillary Action inquiry, pose the question: 'Imagine a world where water molecules were not polar. How would this affect the way water behaves in your body, in plants, and in the environment?' Facilitate a class discussion, guiding students to connect molecular properties to macroscopic effects.

Extensions & Scaffolding

• Challenge students to design a test that compares surface tension between water and another liquid, such as rubbing alcohol or soapy water, and present their findings to the class.
• For students who struggle, provide a sentence starter frame for discussing their observations, such as 'The water rose in the celery stalk because...'
• Deeper exploration: Have students research how animals like water striders use surface tension, then design a model insect that could walk on water based on what they learned.

Key Vocabulary

Polarity	The property of a molecule having a slight positive charge on one end and a slight negative charge on the other, due to uneven electron distribution.
Cohesion	The attraction between molecules of the same substance, causing water molecules to stick together.
Adhesion	The attraction between molecules of different substances, causing water to stick to other surfaces.
Surface Tension	A property of water caused by cohesion, where the surface of the water acts like a thin, invisible film.
Universal Solvent	A substance, like water, that can dissolve many different types of solutes due to its polarity.