Matter, Atoms and Molecules RRB PYQ

A colloid is not a homogeneous mixture; it is a heterogeneous mixture in which very small particles are dispersed throughout another substance. Particles of a colloid are larger than those in a true solution but smaller than those in a suspension. Due to their small size, colloidal particles do not settle down when left undisturbed. They also cannot be separated by ordinary filtration because their particles can pass through filter paper. Colloids show the Tyndall effect, meaning they scatter a beam of light passing through them. Examples include milk, fog, smoke, and starch solution.

Sodium has one electron in its outermost shell. It loses that one electron to achieve a stable, full outer shell, forming a Na+ ion. Chlorine gains that electron to form a Cl- ion, achieving its octet.

The chemical formula of ammonium sulphate is (NH4)2SO4. Ammonium sulphate is an inorganic salt formed by the combination of the ammonium ion (NH4+) and the sulphate ion (SO4^2-). According to the criss-cross method of writing formulas, the valency of the ammonium ion (1) is implied for the sulphate group, while the valency of the sulphate ion (2) becomes the subscript for the ammonium group, giving the resulting compound as electrically neutral, containing two ammonium polyatomic ions for every one sulphate ion.

Covalent molecules have low melting and boiling points because they have weak intermolecular forces. These weak forces require less energy to break, resulting in low melting and boiling points. Water, carbon dioxide, and methane are covalent compounds with relatively low boiling/melting points.

The statement that particles of matter do not have spaces in between them is not true. Particles are in a state of continuous motion, and this movement increases as the temperature rises. Particles exert an attractive force on one another, which keeps them held together; this force is strongest in solids and weakest in gases. All particles of matter have spaces in between them.

Ionic compounds like potassium bromide do not conduct electricity in solid form because ionic bonds prevent ion movement. In solid form, potassium bromide has ions that are locked tightly in a crystal lattice by strong ionic bonds. As the ions can't move, electric current cannot flow. When KBr is melted, the rigid structure breaks down, and ions are free to move, allowing them to carry electric current.

Methane's Lewis structure shows a central carbon atom sharing one electron pair with each of four hydrogen atoms, forming C-H single (sigma) bonds and giving carbon a complete octet. Carbon forms four single covalent bonds with four hydrogen atoms. Each bond shares one pair of electrons.

In graphite, the different layers are held together by Van der Waals forces. These weak intermolecular forces occur due to temporary dipoles created when electrons move around the nucleus. These forces are much weaker compared to the strong covalent bonds within each layer of graphite, where carbon atoms are bonded together in a hexagonal lattice.