Class 9 Chapter 2 Is Matter Around Us Pure?

Class 9 Chapter 2 Is Matter Around Us Pure?                                                                                                                                         

*   **What is a pure substance?** 

    A pure substance is a single form of matter that consists of only one type of particle, and all its constituent particles are the same in their chemical nature.

*   **What is a mixture?** 

    A mixture contains more than one kind of pure substance mixed together in any proportion without reacting chemically.

*   **What is a solution?** 

    A solution is a homogeneous mixture of two or more substances, where particles are evenly distributed and cannot be seen by the naked eye.

*   **What are the two main components of a solution?** 

    A solution consists of a **solvent** (the component present in a larger amount that dissolves the other) and a **solute** (the component dissolved in the solvent).

*   **What is a saturated solution?** 

    A saturated solution is one that has dissolved as much solute as it is capable of dissolving at a specific given temperature.

*   **What is a suspension?** 

    A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the medium and are visible to the naked eye.

*   **What is a colloidal solution (colloid)?** 

    A colloid is a heterogeneous mixture with particles that are too small to be seen with the naked eye but are large enough to scatter a beam of light.

*   **What is the Tyndall effect?** 

    The Tyndall effect is the scattering of a beam of visible light by the particles present in a colloidal solution.

*   **What are the components of a colloidal solution called?** 

    The solute-like particles are called the **dispersed phase**, and the medium in which they are suspended is called the **dispersion medium**.

*   **What is an element?** 

    An element is a basic form of matter that cannot be broken down into simpler substances by chemical reactions.

*   **What are metalloids?** 

    Metalloids are elements like boron and silicon that display intermediate properties between those of metals and non-metals.

*   **What is a compound?** 

    A compound is a substance composed of two or more different elements that are chemically combined with one another in a fixed proportion.

*   **What distinguishes a physical change from a chemical change?** 

    A **physical change** alters a substance without changing its chemical composition (like interconversion of states), whereas a **chemical change** (or chemical reaction) changes the chemical composition of matter to produce new substances.