1. All materials are composed of 92 elements that combine to form compounds or molecules. Elements cannot be broken down further, while compounds and molecules can. 2. Atoms are the smallest particles of elements and join together to form molecules. Atoms themselves contain electrons, protons and neutrons. 3. Materials exist in solid, liquid and gas states depending on the strength of electrostatic forces between atoms and molecules. Stronger forces lead to solids with fixed shapes, while weaker forces allow liquids and gases to flow freely.

11. Chloride atom

12. Observation Explanation Metals are dense The particles present in metals are tightly packed in the lattice. Metals have high melting and boiling points. Strong forces of attraction exist between particles. A Large amount of thermal energy is required to overcome the strong electrical forces between the positive ions and the delocalised electrons. These forces operate throughout the lattice. Metals are good conductors of heat. Delocalised electrons transmit the energy of vibrations of 1 positive ion to its neighbours. Metals are good conductors of electricity. Mobile delocalised electrons within the lattice. Electrons flow in at one end, and the same number flow out the other end. Metals are malleable and ductile. The distortion does not disrupt the metallic bonding.