Scientific Inquiry and the Natural World · 5th Class · Materials and Their Properties · Summer Term

Sublimation and Deposition

Exploring the less common phase changes where solids turn directly into gases and vice versa.

• NCCA Curriculum Specifications
• NCCA: Primary - Materials
• NCCA: Primary - Properties and Characteristics

About This Topic

Sublimation happens when a solid changes directly to a gas without passing through the liquid state, for example dry ice turning into carbon dioxide vapour at room temperature. Deposition is the opposite, gas becoming a solid directly, such as water vapour forming frost on a cold surface. In 5th class, students examine these phase changes under specific conditions like low temperature or pressure, using safe classroom examples to explain the processes and compare them to melting and evaporation.

This topic aligns with the NCCA Primary curriculum on materials and their properties. It builds on prior knowledge of states of matter by introducing less common transitions, helping students analyze how particle energy influences changes. Key questions guide inquiry into real-world examples, fostering skills in observation, prediction, and evidence-based explanation.

Active learning suits this topic well because the processes occur quickly and visibly. Students gain confidence through guided demonstrations and simple experiments, where they record changes, discuss molecular movement, and test predictions. This approach turns abstract ideas into shared experiences that strengthen conceptual understanding and retention.

Key Questions

1. Explain the process of sublimation using dry ice as an example.
2. Analyze the conditions under which sublimation and deposition occur.
3. Compare sublimation to melting and evaporation.

Learning Objectives

• Explain the process of sublimation using dry ice as an example.
• Analyze the conditions required for sublimation and deposition to occur.
• Compare and contrast sublimation and deposition with melting and evaporation.
• Identify real-world examples of sublimation and deposition.

Before You Start

States of Matter

Why: Students must understand the basic properties of solids, liquids, and gases to comprehend how matter changes between these states.

Evaporation and Condensation

Why: Prior knowledge of these common phase changes provides a foundation for understanding the less common processes of sublimation and deposition.

Key Vocabulary

sublimation	The process where a solid changes directly into a gas without becoming a liquid first. Dry ice turning into carbon dioxide gas is a common example.
deposition	The process where a gas changes directly into a solid without becoming a liquid first. Frost forming on a cold window is an example.
phase change	A physical process that results in the transformation of a substance from one solid state to another. This includes melting, freezing, evaporation, condensation, sublimation, and deposition.
particle energy	The amount of kinetic energy that the tiny parts (particles) of a substance have. Higher energy means particles move more, affecting phase changes.

Watch Out for These Misconceptions

Common Misconception

All solids must melt into liquid before becoming gas.

What to Teach Instead

Sublimation skips the liquid phase under low pressure or specific temperatures. Hands-on dry ice demos let students see no liquid form, prompting them to revise models through peer observation and measurement of mass changes.

Common Misconception

Deposition is the same as freezing liquid water.

What to Teach Instead

Deposition involves gas turning solid directly, without liquid. Cold surface experiments reveal frost buildup from air moisture, helping students distinguish processes via timed drawings and group discussions.

Common Misconception

Sublimation only happens with dry ice.

What to Teach Instead

Many substances sublime, like mothballs or snow in dry air. Station rotations expose students to multiple examples, building broader recognition through prediction and evidence collection.

Active Learning Ideas

Demonstration: Dry Ice Sublimation

Place small pieces of dry ice in a clear container with a warm cloth draped over it to trap fog. Students observe the solid disappearing into gas and measure mass loss over time. Discuss safety rules like gloves and ventilation first.

25 min·Whole Class

Experiment: Frost Formation for Deposition

Chill metal cans in a freezer, then place them in humid air. Students watch water vapour deposit as frost, timing the process and noting conditions like temperature. Compare to regular freezing by touching ice cubes.

30 min·Small Groups

Comparison Chart: Phase Changes

Provide diagrams of melting, evaporation, sublimation, and deposition. In pairs, students fill charts with examples, conditions, and particle sketches, then share one key difference with the class.

20 min·Pairs

Inquiry Stations: Sublimation Hunt

Set stations with mothballs, iodine crystals, and dry ice. Groups predict which sublimes, observe over 10 minutes, and rotate to record evidence. Conclude with a class vote on fastest sublimation.

40 min·Small Groups

Real-World Connections

• Freeze-drying, a process used to preserve food and pharmaceuticals, relies on sublimation. By lowering the pressure and temperature, water in the substance turns directly into ice vapor, leaving a dry product.
• The formation of frost on cold surfaces, like car windshields or grass in the early morning, is a direct result of deposition. Water vapor in the air transforms into ice crystals when it contacts a surface below freezing point.

Assessment Ideas

Quick Check

Present students with images of dry ice and frost formation. Ask them to write one sentence for each image explaining which phase change is occurring and why.

Discussion Prompt

Pose the question: 'How is sublimation different from evaporation, and how is deposition different from condensation?' Facilitate a class discussion where students use the key vocabulary to explain the differences.

Exit Ticket

On a small card, ask students to draw a simple diagram showing either sublimation or deposition. They should label the states of matter involved and the direction of the phase change.

Frequently Asked Questions

What is sublimation and deposition in simple terms?

Sublimation is a solid turning straight to gas, like dry ice fogging a glass. Deposition is gas to solid, as in frost on windows. These occur at certain temperatures and pressures. Students connect them to everyday sights, using examples to grasp particle behaviour without intermediate liquids.

How do you demonstrate sublimation safely in 5th class?

Use dry ice with gloves, in well-ventilated areas, small pieces only. Place in containers to show mass loss and fog. Pair with videos for reinforcement. Safety talks build responsibility, while observations spark questions about energy and particles.

What conditions cause sublimation and deposition?

Sublimation needs low pressure or temperatures where vapour pressure exceeds surroundings, speeding solid to gas. Deposition happens when gas cools rapidly below freezing point. Classroom demos with thermometers help students link conditions to visible changes, predicting outcomes.

How can active learning help students understand sublimation and deposition?

Active methods like dry ice handling and frost experiments make invisible phase skips observable. Students predict, test, and discuss in groups, revising misconceptions through evidence. This builds skills in inquiry and collaboration, as shared stations reveal patterns no lecture matches, deepening retention of molecular concepts.