phase changes
predictions
1. how does adding energy to a solid affect the motion of the particles?
2. how can a gas at room temperature (like oxygen) become solid?
experiment
test your predictions using this simulation (click phase changes).
1. start with solid argon and explain how to make argon change to the liquid state and then to the gaseous state.
2. start with gaseous argon and explain how to make the argon change to the liquid state and then to the solid state.
3. explain how the absorption of energy (heating) affects the speed of the particles in a substance.
4. explain how the release of energy (cooling) affects the speed of the particles in a substance.
5. can you make the particles of any of the substances stop moving?
making connections
1. when you apply heat energy to a substance, where does the energy go? think about the law of conservation of energy

Question

Accepted Answer

### Predictions 1
# Explanation:
## Step1: Recall particle motion in solids
In a solid, particles vibrate in fixed positions.
## Step2: Analyze energy addition effect
Adding energy (heating) increases the kinetic energy of particles. So, the particles vibrate more vigorously, with greater amplitude and speed.
# Answer:
Adding energy (heating) to a solid increases the kinetic energy of its particles, causing them to vibrate more vigorously (with greater speed and amplitude) in their fixed positions.

### Predictions 2
# Explanation:
## Step1: Recall phase change to solid
To change a gas to a solid (deposition), we need to remove energy (cool) it significantly.
## Step2: Apply to oxygen gas
For oxygen (a gas at room temp), we must lower its temperature far below its freezing point (and also can increase pressure, though temperature is key here) to remove enough energy so the gas particles slow down, come closer, and arrange into a solid structure.
# Answer:
To make a gas like oxygen become solid, we need to **remove a large amount of energy (cool it drastically)** to lower its temperature below its freezing point (and can also increase pressure). This causes the gas particles to lose kinetic energy, slow down, and arrange into a solid structure (deposition).

### Experiment 1
# Explanation:
## Step1: Solid to liquid (melting)
Solid argon has particles vibrating in fixed positions. To melt it (solid → liquid), we add energy (heat it) until it reaches its melting point. This energy increases particle kinetic energy, allowing them to break free from the rigid solid structure and move more freely (liquid state).
## Step2: Liquid to gas (vaporization)
To change liquid argon to gas, we add more energy (heat it) until it reaches its boiling point. This further increases particle kinetic energy, so particles move even faster and escape the liquid’s intermolecular forces to become a gas (gaseous state).
# Answer:
- **Solid Argon → Liquid Argon**: Add energy (heat) until argon reaches its melting point. The added energy increases particle kinetic energy, allowing them to break free from the rigid solid structure and move more freely (liquid state).
- **Liquid Argon → Gaseous Argon**: Add more energy (heat) until argon reaches its boiling point. The additional energy further increases particle kinetic energy, so particles move fast enough to escape the liquid’s intermolecular forces and become a gas.

### Experiment 2
# Explanation:
## Step1: Gas to liquid (condensation)
Gaseous argon has particles moving rapidly and freely. To condense it (gas → liquid), we remove energy (cool it) until it reaches its condensation point (same as boiling point, reversed). This lowers particle kinetic energy, so particles slow down and come closer, forming a liquid.
## Step2: Liquid to solid (freezing)
To freeze liquid argon (liquid → solid), we remove more energy (cool it) until it reaches its freezing point (same as melting point, reversed). This further lowers particle kinetic energy, so particles slow down enough to arrange into a rigid solid structure.
# Answer:
- **Gaseous Argon → Liquid Argon**: Remove energy (cool it) until argon reaches its condensation point (boiling point). The removed energy decreases particle kinetic energy, so particles slow down, come closer, and form a liquid (condensation).
- **Liquid Argon → Solid Argon**: Remove more energy (cool it) until argon reaches its freezing point (melting point). The additional energy removal lowers particle kinetic energy further, so particles slow down and arrange into a rigid solid structure (freezing).

### Experiment 3
# Explanation:
## Step1: Energy absorption (heating)
When a substance absorbs energy (is heated), this energy is converted into **kinetic energy** of its particles.
## Step2: Effect on particle speed
Increased kinetic energy means particles move faster (higher speed). For example, in a solid, heating makes particles vibrate more vigorously; in a liquid, they move more freely; in a gas, they move faster and collide more.
# Answer:
Absorbing energy (heating) **increases the speed of particles** in a substance. The added energy increases their kinetic energy, causing them to move (or vibrate) faster.

### Experiment 4
# Explanation:
## Step1: Energy release (cooling)
When a substance releases energy (is cooled), it loses kinetic energy.
## Step2: Effect on particle speed
Losing kinetic energy means particles slow down. In a gas, cooling makes particles move slower and come closer (condensation); in a liquid, they slow down more (freezing into a solid).
# Answer:
Releasing energy (cooling) **decreases the speed of particles** in a substance. The lost energy reduces their kinetic energy, causing them to move (or vibrate) slower.

### Experiment 5
# Explanation:
## Step1: Recall particle motion theory
According to the kinetic theory of matter, particles are always in motion (even in solids, they vibrate). The only way to stop particle motion is to reach absolute zero ($0\ 	ext{Kelvin}$ or $-273.15^\circ	ext{C}$), where theoretical kinetic energy is zero.
## Step2: Practicality
Absolute zero is a theoretical limit and cannot be reached in practice (due to the third law of thermodynamics). So, we cannot make particles stop moving completely in any substance we can work with.
# Answer:
No, we cannot make the particles of any substance stop moving completely. Particles are always in motion (per the kinetic theory of matter), and absolute zero ($0\ 	ext{K}$), where motion would theoretically stop, is unattainable in practice (third law of thermodynamics).

### Making Connections 1
# Explanation:
## Step1: Law of conservation of energy
Energy cannot be created or destroyed, only transferred or transformed.
## Step2: Apply to heating a substance
When we apply heat energy to a substance, the energy is **transferred to the particles** of the substance. It becomes kinetic energy (increasing particle motion/speed) and can also break intermolecular forces (for phase changes: melting, vaporization, etc.). This energy is either used to increase temperature (sensible heat) or change phase (latent heat), but it is never “lost”—it is transferred to the substance’s particles or surroundings (but in the substance, it increases particle energy).
# Answer:
When heat energy is applied to a substance, the energy **is transferred to the substance’s particles** (per the law of conservation of energy). It becomes kinetic energy (increasing particle motion/speed) and/or is used to break intermolecular forces (for phase changes like melting or vaporization). The energy is not destroyed—it is transferred to the substance (increasing its internal energy) or to the surroundings (but in the substance, it increases particle energy).

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QUESTION IMAGE

Question

Explanation:

Predictions 1

Step1: Recall particle motion in solids

Step2: Analyze energy addition effect

Step1: Recall phase change to solid

Step2: Apply to oxygen gas

Step1: Solid to liquid (melting)

Step2: Liquid to gas (vaporization)

Answer:

Predictions 2