Unit 5 - Phase Change

Unit 5 - Phase Change

by S Harris

​Learning Target

​I know...

• ​how to define the 6 different phase changes

​Success Criteria

​I can...

• ​correctly label and explain a phase diagram.

Characteristics of Phase changes

​Phase change is the reversible PHYSICAL CHANGE that occurs when a substance changes from one state of matter to another

• The 6 common phase changes include:

  • Melting, freezing, vaporization, condensation, sublimation, and deposition

• All phase changes share certain characteristics related to energy and temperature

​Temperature and Phases Changes

• ​One way to recognize a phase change is by measuring the temperature of the substances as it is heated or cooled

  • The temperature of a substance does not change during a phase change, so that means:

    • the temperature will remain constant during a phase change

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​Energy and Phase Changes

​

• ​During a phase change, energy is transferred between a substance and its surroundings

• Energy is either absorbed or released during a phase change

  • Endothermic change the system ABSORBS energy from its surroundings

  • Exothermic change the system RELEASES energy to its surroundings

Multiple Choice

We can recognize a phase change by measuring the ___________ of a substance as it is heated/cooled

• time

• pressure

• speed

• temperature

Multiple Choice

Is a phase change a physical or chemical change?

• physical

• chemical

​1. Melting

​

• ​Melting is when energy is added to a solid object and it turns into a liquid.

  • The average kinetic energy of the molecules increases and the temperature rises

    • This phase change is ENDOTHERMIC

​2. Freezing

​

• ​Freezing is when energy is removed form an object and it goes from a liquid to a solid.

  • As the average kinetic energy decreases, the molecules move more slowly

  • This is EXOTHERMIC

​

​3. Vaporization (Boiling)

​

• ​Vaporization (Boiling) is when a substance changes from a liquid into a gas

• Vaporization is an endothermic process

  • the substance has to absorb energy to change from a liquid to a gas

    • As the temperature increases the molecules move faster and faster (kinetic theory)

​

Multiple Choice

What phase change is occurring in the image.

• melting

• freezing

• boiling

• vaporization

Multiple Choice

During what phase change does a liquid become a gas?

• melting

• freezing

• vaporization

• sublimation

​4. Condensation

​

• ​Condensation is the phase change in which a substance changes from a gas to a liquid

• Condensation is an EXOTHERMIC process

​

5. Sublimation

• ​Sublimation is the phase change in which a substance changes from a solid to a gas or vapor without changing to a liquid first

  • Dry Ice (solid carbon dioxide) at room temperature goes from solid to gas and forms a “fog”

  • Sublimation is ENDOTHERMIC

​

​6. Deposition

• ​Deposition is when a gas or vapor changes directly into a solid without first changing to a liquid

  • Deposition causes frost to form on car windows

  • This is EXOTHERMIC (release energy as heat)​

Multiple Choice

During a CONDENSATION phase change, will the particles speed increase or decrease as the substance changes phase? (hint: think about kinetic energy in the phases and what phase change is happening here)

• increase

• decrease

Multiple Choice

During DEPOSITION is the temperature increasing or decreasing? (hint: think about the phase change and if this happens if heat is added or removed)

• increasing

• decreasing

​Phase Change Diagram Practice

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​What is occurring at the following point?

​

​Point D:

• phase(s): ​only solid at this point

• description: temperature is increasing

​Phase Change Diagram Practice

​

​What is occurring at the following point?

​

Point B:

• phase(s): ​solid to liquid at this point

• description: temperature is constant; melting point

​Phase Change Diagram Practice

​

​What is occurring at the following point?

​

​

Point C:

• phase(s): only liquid at this point

• description: temperature is increasing

​Phase Change Diagram Practice

​

​What is occurring at the following point?

​

​Point A:

• Phase(s): liquid to gas at this point

• description: temperature is constant (flat line); boiling point

​Phase Change Diagram Practice

​

​What is occurring at the following point?

​

​Point E:

• phase(s): only gas at this point

• description: temperature is increasing

REMEMBER!!!

​If there is a flat line, that indicates that there is NO temperature change.

​Phase Change Diagram Combined

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