A compound, X, has a melting point of 71°C and a boiling point of 375°C.
Which statement about X is correct?
A) It is a liquid at 52°C and a gas at 175°C.
B) It is a liquid at 69°C and a gas at 380°C.
C) It is a liquid at 75°C and a gas at 350°C.
D) It is a liquid at 80°C and a gas at 400°C.
▶️ Answer/Explanation
Ans: D
To determine the state of a substance at different temperatures, we compare the given temperature to its melting and boiling points:
- Below melting point: solid
- Between melting and boiling points: liquid
- Above boiling point: gas
Analyzing each option:
A) 52°C is below melting point (should be solid), 175°C is below boiling point (should be liquid). Incorrect.
B) 69°C is below melting point (should be solid), 380°C is just above boiling point (correct for gas). Partially correct but not fully.
C) 75°C is above melting point (correct for liquid), but 350°C is below boiling point (should be liquid, not gas). Incorrect.
D) 80°C is above melting point (correct for liquid), 400°C is above boiling point (correct for gas). Fully correct.
Which statement describes a liquid at room temperature?
A) A sample of a liquid has a fixed volume and shape.
B) A sample of a liquid does not have a fixed volume or shape.
C) The particles are touching but can move by sliding over each other.
D) The particles spread out and fill all available space.
▶️ Answer/Explanation
Ans: C
Let’s analyze each option:
A) Incorrect – Liquids have fixed volume but not fixed shape (they take the shape of their container).
B) Incorrect – Liquids do have fixed volume, though they don’t have fixed shape.
C) Correct – This accurately describes the particle arrangement and movement in liquids. The particles are close together (touching) but can move past one another.
D) Incorrect – This describes gas particles, not liquid particles.
Which conditions cause gas particles to move the fastest and the furthest apart?
| temperature | pressure | |
|---|---|---|
| A | high | high |
| B | low | high |
| C | high | low |
| D | low | low |
▶️ Answer/Explanation
Ans: C
Gas particles move fastest at high temperatures because temperature is directly related to the kinetic energy of particles. At higher temperatures, particles have more energy and move faster.
Particles move furthest apart at low pressures because there’s more space between them when the pressure is reduced. High pressure forces particles closer together.
Therefore, the combination that causes gas particles to move fastest and furthest apart is high temperature and low pressure.
The table shows some information about the three states of matter.
| particle separation | particle arrangement | type of motion | |
|---|---|---|---|
| 1 | touching with some particles having spaces between them | random | slide past each other at low speed |
| 2 | particles are far apart | random | rapid motion in straight lines |
| 3 | touching with very little space between the particles | regular | vibration only |
Which row is correct?
| 1 | 2 | 3 | |
|---|---|---|---|
| A | gas | liquid | solid |
| B | liquid | solid | gas |
| C | liquid | gas | solid |
| D | solid | gas | liquid |
▶️ Answer/Explanation
Ans: C
Let’s analyze each state:
State 1: Particles touching with some spaces, random arrangement, sliding past each other – these are characteristics of a liquid.
State 2: Particles far apart, random arrangement, rapid motion – these are characteristics of a gas.
State 3: Particles touching with little space, regular arrangement, vibrating only – these are characteristics of a solid.
Therefore, the correct matching is: 1 = liquid, 2 = gas, 3 = solid, which corresponds to option C.