Glossary
Adhesive Forces
Attractive forces between molecules of different substances, causing them to stick to each other.
Example:
The adhesive forces between water molecules and the glass walls of a graduated cylinder cause the water to 'climb' slightly up the sides.
Amorphous Solid
A solid in which the particles lack a long-range, ordered arrangement, exhibiting a disordered structure.
Example:
Glass is an amorphous solid because its silicon dioxide molecules are randomly arranged, unlike the ordered structure of a quartz crystal.
Capillary Action
The spontaneous rising of a liquid in a narrow tube or porous material, caused by the interplay of adhesive and cohesive forces.
Example:
When you place a paper towel into spilled juice, capillary action causes the liquid to climb up the towel against gravity.
Cohesive Forces
Attractive forces between molecules of the same substance, causing them to stick together.
Example:
Water molecules exhibit strong cohesive forces, which is why water forms spherical droplets on a waxed surface.
Concave Meniscus
A downward-curving liquid surface that occurs when adhesive forces between the liquid and the container are stronger than the cohesive forces within the liquid.
Example:
Water in a glass beaker forms a concave meniscus because the water molecules are more attracted to the glass than to each other.
Convex Meniscus
An upward-curving liquid surface that occurs when cohesive forces within the liquid are stronger than the adhesive forces between the liquid and the container.
Example:
Mercury in a glass thermometer forms a convex meniscus because its atoms are more strongly attracted to each other than to the glass.
Crystalline Solid
A solid in which the particles are arranged in a highly ordered, repeating three-dimensional pattern.
Example:
Table salt (NaCl) is a crystalline solid where sodium and chloride ions form a precise, repeating cubic structure.
Density
A physical property of matter defined as mass per unit volume (D = m/V), indicating how much 'stuff' is packed into a given space.
Example:
A block of lead has a much higher density than a block of wood of the same size because lead atoms are much more massive and closely packed.
Gas
A state of matter characterized by particles that are widely dispersed and move rapidly and randomly, taking both the shape and volume of their container.
Example:
The air inside a balloon is a gas, expanding to fill the entire volume of the balloon and taking its spherical shape.
Intermolecular Forces (IMFs)
Attractive forces that exist between molecules, influencing a substance's physical properties like boiling point, surface tension, and viscosity.
Example:
The strong hydrogen bonding intermolecular forces in water are responsible for its unusually high boiling point compared to other similar-sized molecules.
Liquid
A state of matter characterized by particles that are close together but can move past one another, giving it a definite volume but an indefinite shape.
Example:
Honey is a liquid that takes the shape of its container but maintains its own volume, and its molecules can flow past each other.
Matter
Anything that has mass and occupies space. It is the fundamental substance of which all physical objects are composed.
Example:
A student's backpack, filled with textbooks and a laptop, is a clear example of matter because it has both mass and takes up space.
Meniscus
The curved surface of a liquid in a container, formed due to the relative strengths of cohesive and adhesive forces.
Example:
When reading the volume of a liquid in a graduated cylinder, you must read from the bottom of the meniscus for accuracy.
Solid
A state of matter characterized by particles that are tightly packed in fixed positions, resulting in a definite shape and volume.
Example:
A diamond is a solid because its carbon atoms are rigidly held in a crystalline lattice, giving it a fixed shape and volume.
States of Matter
The distinct forms in which matter can exist, primarily characterized by differences in particle arrangement, movement, and intermolecular forces.
Example:
Water can exist in three common states of matter: solid ice, liquid water, and gaseous steam, each with unique properties.
Surface Tension
The cohesive force that causes the surface of a liquid to resist external force and behave like an elastic film, minimizing its surface area.
Example:
A water strider can walk on the surface of a pond due to the high surface tension of water, which supports its weight.
Viscosity
A liquid's resistance to flow, determined by the strength of its intermolecular forces and temperature.
Example:
Maple syrup has a much higher viscosity than water, which is why it pours slowly over your pancakes.