Test: Matter - Grade 7 MCQ

Adhesion refers to the force of attraction between different kinds of molecules. For example, when glue bonds paper and glass, it is due to the adhesive force. This concept is crucial in understanding how different materials interact with each other.

Cohesion refers to the attraction between similar molecules. An example is water droplets forming on a leaf, where water molecules are attracted to each other, creating a droplet shape due to cohesive forces.

The Kinetic Theory of Matter states that matter is composed of small particles (atoms and molecules) that are always in motion. This theory helps explain the behavior of gases, liquids, and solids under different conditions.

When a solid is heated, its molecules vibrate more vigorously in their fixed positions rather than moving freely. This increased vibration can lead to slight expansion, but the solid remains in its fixed shape.

Gases have the most loosely packed molecules, allowing them to move freely and occupy more space. This property makes gases highly compressible compared to solids and liquids.

Ice melting into water is an example of a physical change because it involves a change in state from solid to liquid without altering the chemical composition of the water. Physical changes can often be reversed, unlike chemical changes.

The primary factor that differentiates solids from liquids is the arrangement and movement of molecules. In solids, molecules are closely packed and vibrate in place, while in liquids, they are less tightly packed and can move freely.

Boiling is the process where a liquid changes into a gas, usually through heating. During boiling, the molecules gain enough energy to overcome intermolecular forces and escape into the gas phase.

The primary characteristic of molecules in gases is that they are free to move in all directions. This freedom allows gases to expand and fill their containers, resulting in no fixed shape or volume.

The strength of intermolecular forces directly influences the rigidity and hardness of materials. For instance, materials with strong intermolecular forces, like metals, are often harder compared to those with weaker forces, such as chalk.

Liquids have more space between their molecules than solids do. This increased intermolecular space allows liquid molecules to move around each other, giving liquids their fluidity and ability to take the shape of their container.

Melting is the process where a solid changes into a liquid upon heating. During melting, the energy supplied allows the molecules in the solid to overcome their rigid arrangement and move more freely.

Gases take the shape and volume of their container because their molecules are very loosely packed and move freely in all directions. This property allows gases to fill any available space.

John Dalton is credited with proposing that matter is composed of tiny particles called molecules. His work laid the foundation for modern atomic theory, which is crucial in understanding the structure of matter.

Condensation is the process that occurs when a gas cools and transitions into a liquid state. This process involves the loss of energy by gas molecules, allowing intermolecular forces to pull them closer together.

Solids have a fixed shape and volume due to the strong intermolecular forces that keep the molecules closely packed. This characteristic distinguishes solids from liquids and gases, which do not have a fixed shape.

When a substance is heated, the intermolecular forces typically weaken, allowing the molecules to gain energy and move apart. This change is key to processes like melting and boiling, where the state of matter changes.

An atom is defined as the smallest unit of an element that can exist independently and participate in chemical reactions. Atoms combine in various ways to form molecules, which are the smallest units of matter that retain the properties of that substance.

Diffusion is the process where molecules move from an area of higher concentration to an area of lower concentration, resulting in the spreading of ink in water. This illustrates the constant movement of molecules in liquids.

Plasma is a state of matter that occurs at extremely high temperatures, where electrons are separated from their nuclei, resulting in a mixture of charged particles. This state is commonly found in stars, including the sun.