Revision: Matter in Our Surroundings Science English Medium Class 9 CBSE

Matter—Anything that has mass and occupies space is called matter.

Anything that has mass and occupies space is called matter.

An emulsion is a colloid in which minute droplets of one liquid are dispersed in another liquid which is not miscible with it. Examples are milk and butter.

The matter is defined as anything that has mass and takes up space. The matter is found in solid, liquid and gas.

Atom — An atom is the smallest part of an element that takes place in a chemical reaction.

• Matter is defined based on its physical and chemical structure. It occupies space and has mass, particularly as opposed to energy.
• Atoms and molecules are the building blocks of matter, consisting of positively charged protons, neutral neutrons, and negatively charged electrons, respectively.

Chemical properties of matter tell us how a substance changes when it interacts with other substances. These properties describe how matter reacts and forms new substances. When a chemical change happens, the matter changes into something new. The atoms in a substance rearrange themselves, and a new substance is formed. For example:

• When wood burns, it turns into ash and smoke.
• When iron is exposed to air and water, it forms rust.

Examples of Chemical Properties:

• Flammability: This describes if a substance can burn. For example, wood is flammable because it can catch fire.
• Reactivity: This tells us how a substance reacts when mixed with others. For example, if you mix vinegar with baking soda, they react to create bubbles.
• Rusting: Some metals, like iron, will form rust when they come in contact with water and air.
• Acidity and Basicity: Some substances are acidic (like lemon juice), while others are basic (like soap). Acids and bases can react with each other to form new substances.

A solid is that state of matter which has a fixed shape, mass, and volume. It suffers very small changes in volume by changing the temperature. It can not be compressed.
e.g. – Sand, Wood, Copper, Ice, etc.

Intermolecular force — The force of attraction between the molecules of a given substance is called intermolecular force.

The amount of space occupied by a matter is called its volume.

It is a state of matter which has only definite mass but no definite shape and volume. It takes up the shape of the container
e.g. – Carbon dioxide, oxygen, etc.

The process by which matter changes from one state to another and back to original state, without any change in its chemical composition.

Molecule — A molecule is a smallest part of a compound that exists independently.

It has a definite mass and volume but lacks a shape of its own. It takes up the shape of the containing vessels. It can be compressed to an extent,
e.g. – Milk, water, ink, etc.

Mass is the quantity of matter contained in the body.

The triple point of water is that point where water in a solid, liquid and gas state co-exists in equilibrium and this occurs only at a unique temperature and a pressure.

Sublimation is the process in which a solid changes directly into a gas on heating, without passing through the liquid state.

A transition from one state to another is called a change of state (or phase change).

Or

The process of change from one state to another at a constant temperature is called the change of phase.

It can be defined as the fixed temperature at which a solid start changing to its liquid state is Melting Point

The physical process that results in the transition of a substance from the solid-state to the liquid state on heating at a fixed temperature is called Melting.

Heat energy is absorbed by a solid during melting and an equal amount of heat energy ‘ is liberated by the liquid during freezing, without any temperature change. It is called the latent heat of fusion.

Melting or fusion: The process in which a solid is converted to a liquid by absorbing heat is called melting or fusion.

The change from liquid to gas (or vapour) phase on absorption of heat at a constant temperature, is called vaporisation.

The particular temperature at which vaporisation occurs is called the boiling point of liquid.

The change from vapour to liquid phase on liberation of heat at a constant temperature is called condensation (or liquefaction) and the particular temperature at which the condensation occurs is called the condensation point of vapour.

The change of a solid substance directly into a gas or vapour without first changing into a liquid is called sublimation.

OR

The change from solid state to vapour state without passing through the liquid state is called sublimation, and the substance is said to sublime.

The change of state from solid to gas directly is called sublimation.

• A change of state occurs when heat exchange causes a substance to transition between solid, liquid, and gas phases.
• Temperature remains constant during a phase change because heat energy changes molecular arrangement (potential energy), not molecular speed (kinetic energy).
• The heating curve has flat plateaus at the melting point (0 °C) and boiling point (100 °C) for water, with rising slopes in between.