Question

skill practice & self reflection
skill 1:
explain how the kinetic energy of particles changes as a substance undergoes phase changes.
practice: fill in the blanks to make true statements using the words increase or decrease.

1. as gas becomes a liquid, the kinetic energy ____________.
2. when kinetic energy ____________ a solid will melt into a liquid.
3. in order for a substance to freeze from a liquid to a solid the kinetic energy must ____________.
4. liquids becoming gas requires ____________ kinetic energy.
5. use the statements that you completed above to describe the law of conservation of energy and how it relates to kinetic energy.

self reflection:
☐ i can explain how the kinetic energy of particles changes as a substance undergoes phase changes.
additional notes/evidence:

Explanation:

Step1: Phase change from gas to liquid

When a gas becomes a liquid (condensation), the particles slow down. Kinetic energy \(KE=\frac{1}{2}mv^{2}\), and slower - moving particles (lower \(v\)) have lower kinetic energy. So, it is a decrease.

Step2: Melting of solid

Melting (solid to liquid) requires adding energy. This added energy increases the motion of particles. Using \(KE = \frac{1}{2}mv^{2}\), more energetic (faster - moving, higher \(v\)) particles mean higher kinetic energy. So, it is an increase.

Step3: Freezing of liquid

Freezing (liquid to solid) is the opposite of melting. Energy is removed. Particles slow down. From \(KE=\frac{1}{2}mv^{2}\), slower particles (lower \(v\)) have lower kinetic energy. So, it is a decrease.

Step4: Vaporization of liquid

Liquids becoming gas (vaporization) requires adding energy. Particles gain energy and move faster. Using \(KE=\frac{1}{2}mv^{2}\), faster - moving particles (higher \(v\)) have higher kinetic energy. So, it is an increase.

Step5: Law of conservation of energy

The law of conservation of energy (\(E_{total}\) is constant) means that the energy changes (in terms of kinetic energy) during phase changes are just transfers. When kinetic energy increases (e.g., melting, vaporization), it is because energy is input (from an external source), and when it decreases (e.g., condensation, freezing), energy is output (to the surroundings), but the total energy of the system and surroundings remains constant.

Answer:

1. decrease
2. increase
3. decrease
4. increase
5. The law of conservation of energy states that energy cannot be created or destroyed, only transferred or transformed. In phase changes, kinetic energy is transferred. For example, when a gas becomes a liquid (1), kinetic energy decreases (energy is transferred out). When a solid melts (2), kinetic energy increases (energy is transferred in). Freezing (3) involves a decrease in kinetic energy (energy out), and liquid - to - gas (4) requires an increase (energy in). So, kinetic energy changes are part of energy transfer processes that follow the law of conservation of energy.