Question

phase changes
graph: temperature (k) vs. time, segments labeled 1–5
which number of the graph shows where the substance has no shape and no volume?
a 2
b 5
c 4
d 1
e 3
part d
which number on the graph shows where the substance particles are tightly packed?
a 2
b 5
c 4
d 3
e 1
part e
what is the melting point?
what is the freezing point?

Explanation:

First Question (Substance has no shape and no volume)

A substance with no shape and no volume is in the gas phase. In a phase change graph, the gas phase is typically the region where temperature is changing after the liquid - gas phase change (the last sloped region or the region after the second plateau for cooling, here region 5? Wait, no, wait. Wait, when cooling: region 1 is gas cooling (but gas has no shape or volume, but wait, region 1: initial state, maybe gas? Wait, no, let's recall phase change graphs. For a cooling curve (temperature vs time), region 1: gas (no shape, no volume) cooling, region 2: condensation (gas to liquid, constant temp), region 3: liquid cooling, region 4: freezing (liquid to solid, constant temp), region 5: solid cooling (solid has definite shape and volume). Wait, no, the question is "where the substance has no shape and no volume" which is gas. So region 5? Wait, no, maybe I got the graph wrong. Wait, the first question options: A 2, B 5, C 4, D 1, E 3. Wait, maybe the graph is a cooling curve. Let's re - think: Gas has no shape, no volume. In the cooling curve, when the substance is gas, which region? Let's see the temperature axis. Region 1: high temperature, gas (because gas is at high temp in cooling curve before condensation). Wait, no, maybe the correct answer is B (5)? Wait, no, solid has shape and volume, liquid has volume but no fixed shape, gas has neither. So in the cooling curve, after freezing (region 4 is freezing, liquid to solid), region 5 is solid (has shape and volume). Wait, maybe I messed up. Wait, the first question: "substance has no shape and no volume" is gas. So in the graph, region 1: gas (before condensation, region 2 is condensation (gas to liquid, constant temp)), region 3: liquid (cooling), region 4: freezing (liquid to solid, constant temp), region 5: solid (cooling). Wait, that can't be. Wait, maybe the graph is a heating curve? No, the temperature is decreasing, so it's a cooling curve. Wait, maybe the initial state (region 1) is gas (high temp, no shape, no volume), region 2: condensation (gas to liquid, temp constant), region 3: liquid cooling (has volume, no fixed shape), region 4: freezing (liquid to solid, temp constant), region 5: solid (has shape and volume). So the substance with no shape and no volume is gas, which is region 1? But option D is 1. Wait, but maybe I made a mistake. Wait, the answer for the first question (substance has no shape and no volume) is B? No, let's check the options again. The options are A 2, B 5, C 4, D 1, E 3. Wait, maybe the graph is labeled differently. Alternatively, maybe the correct answer is B (5) is wrong, D (1) is gas. So for the first question, the answer is D.1? Wait, no, maybe I got the phases wrong. Let's recall: Gas: no shape, no volume. Liquid: no shape, has volume. Solid: has shape, has volume. So in the cooling curve:

• Region 1: Gas (cooling, temperature decreasing, no shape, no volume)
• Region 2: Condensation (gas to liquid, temperature constant)
• Region 3: Liquid (cooling, temperature decreasing, no shape, has volume)
• Region 4: Freezing (liquid to solid, temperature constant)
• Region 5: Solid (cooling, temperature decreasing, has shape, has volume)

So the substance with no shape and no volume is in region 1 (gas). So the answer is D.1.

Part D (Substance particles are tightly packed)

Particles are tightly packed in the solid phase. In the cooling curve, the solid phase is region 5? Wait, no, region 5 is solid cooling. Wait, region 4 is freezing (liquid to solid), region 5 is solid. But the options are A 2, B 5, C 4, D 3, E 1. Wait, solid particles are tightly packed. So region 5 is solid, but let's check the options. Wait, maybe region 1 is gas (particles far apart), region 2 is condensation (gas to liquid, particles closer), region 3 is liquid (particles closer than gas, farther than solid), region 4 is freezing (liquid to solid), region 5 is solid (particles tightly packed). So the answer should be B.5? No, wait, maybe region 1 is gas (particles not tightly packed), region 2 is liquid - gas transition, region 3 is liquid (particles more packed than gas), region 4 is liquid - solid transition, region 5 is solid (particles tightly packed). So the answer is B.5? But let's check the options again. The question is "where the substance particles are tightly packed" which is solid. So region 5 is solid, so the answer is B.5? Wait, no, maybe I made a mistake. Wait, the options for Part D: A 2, B 5, C 4, D 3, E 1. So if solid is region 5, then B.5. But let's think again. When the substance is solid, particles are tightly packed. In the cooling curve, after freezing (region 4), region 5 is solid. So the answer is B.5.

Part E (Melting point)

Step1: Identify the phase change for melting

Melting is the transition from solid to liquid, which occurs at the same temperature as freezing (liquid to solid) in a phase change graph. In the cooling curve, the freezing point (and thus melting point, since they are equal for a pure substance) is the temperature at the plateau during the liquid - solid phase change (region 4). Looking at the graph, the temperature at region 4 (the plateau) is 220 K (from the y - axis, the temperature at the horizontal line of region 4 is 220 K).

Step2: Confirm the melting point

Since melting point = freezing point for a pure substance, and the freezing point (the temperature at which liquid turns to solid, region 4) is 220 K, the melting point is also 220 K.

Answer:

220 K

Freezing point (assuming the question is about freezing point)