Properties of Gases, Solids, and Liquids

10 Questions

What is the primary reason for the difference in velocities of the two components of light in a crystal, as observed in double refraction?

The difference in the refractive index of the material

Which of the following is a characteristic of liquid molecules according to the kinetic-molecular theory?

They are close but untidy and can move relative to each other

What is the primary reason for the expansion of gases when heated?

The increase in the kinetic energy of the molecules

What is the significance of liquid crystals in detecting areas of elevated temperature under the skin?

They show color changes with temperature

What is a characteristic of solid molecules according to the kinetic-molecular theory?

They are close and tidy and can only vibrate

What is the relationship between the speed of gas molecules and temperature?

The speed of molecules increases when the temperature increases

What is the primary reason for the formation of lyotropic liquid crystals?

The action of certain solvents on solids

What is the significance of liquid crystals in developing display systems such as LCD?

They are sensitive to electric fields

What is a characteristic of gas molecules according to the kinetic-molecular theory?

They are very distant and in continuous movement

What is the primary assumption of the kinetic-molecular theory?

Molecules are in continuous movement and have empty spaces between them

Study Notes

Properties of States of Matter

Solids have a definite volume that does not change, and they cannot change their shape easily.
Liquids have a definite volume that does not change, but they can flow and change their shape.
Gases take up all the available space, take the shape of their container, can compress into a small space, and can expand.

Behavior of Substances in Liquid & Solid States

Liquids and solids compress in very small proportion because the molecules are close, and repulsive forces appear when they try to approach.
Solids do not flow and keep their shape, while liquids can flow and do not keep their shape.
Solids and liquids practically do not expand, and when they do, it is in very small proportion.

Solid State

Types of solid include amorphous and crystalline solids.
Amorphous solids have molecules arranged in a random manner, tend to flow when subjected to sufficient pressure, and do not have definite melting points.
Crystalline solids have particles arranged in a specific manner, cannot flow, and have sharp melting points.
Examples of crystalline solids include sodium chloride crystal and diamonds.

Characterization of Crystalline Solids

Methods of characterization include X-ray diffraction, melting point and heat of fusion, and double refraction of light.

Liquid Crystalline State

The liquid crystalline state can result from heating of the solid (thermotropic liquid crystals) or the action of certain solvents on solids (lyotropic liquid crystals).
Liquid crystals are used to detect areas of elevated temperature under the skin and in developing display systems (e.g., LCD).

Kinetic-Molecular Theory

The kinetic-molecular theory explains the behavior of matter based on the following assumptions:
- Any material thing of the universe has a very large number of very tiny particles called “molecules” that are in continuous movement.
- Molecules are not all equal, but they can have different sizes depending on the type of material.
- Among molecules, there are empty spaces.
The kinetic-molecular theory also explains the behavior of molecules in different states:
- Solid molecules are close, tidy, and can only vibrate.
- Liquid molecules are close, untidy, and move relative to each other.
- Gas molecules are very distant, in continuous movement, and crash into each other and into every object that surrounds them.

Behavior of Substances in Gaseous State

Gases expand when heated, and their speed of molecules depends on their temperature, increasing with temperature and decreasing with temperature.