Razi

Non-metals are elements that mostly lack the properties of metals and can exist as gases, liquids, or solids. They are usually dull and not shiny, except for some like iodine. Non-metals are generally poor conductors of heat and electricity, with an exception being graphite, a form of carbon that can conduct electricity. Their melting points tend to be lower than metals, and they are brittle, meaning they break easily and cannot be bent or shaped. Chemically, non-metals have high electronegativity and ionization energy, so they tend to gain electrons in reactions, forming negative ions and acidic oxides when combined with oxygen. Non-metals include elements such as carbon, sulfur, iodine, oxygen, and hydrogen. Some non-metals, like carbon, show allotropy, existing in different forms with distinct physical properties, such as diamond and graphite. Non-metals do not exhibit malleability or ductility, unlike metals, and they do not produce metallic bonding which accounts for…

Muscles are soft tissues in the human body made up of special cells called muscle fibers that can contract and relax. They help the body move by pulling on bones through tendons. Muscles are elastic, which means they can contract without breaking and then return to their original shape. There are over 600 muscles in the human body, and together with bones and joints, they allow all kinds of body movements. Muscles also protect our organs and help maintain posture and body stability. They can be divided into three main types: skeletal muscles, which are attached to bones and help with voluntary movements; smooth muscles, found inside organs and responsible for involuntary actions; and cardiac muscles, which are found only in the heart and control heartbeat. The nervous system directs muscles to contract and relax so we can move and perform tasks. Muscle contractions convert chemical energy into mechanical energy…

Joints in the human body are of three main types: fibrous, cartilaginous, and synovial. Fibrous joints are immovable and hold bones tightly together, like in the skull. Cartilaginous joints allow limited movement and connect bones with cartilage, found in areas like the spine. Synovial joints are freely movable and the most common, allowing different kinds of motion. Among synovial joints are hinge joints, which move back and forth like elbows and knees. Ball and socket joints enable rotation and movement in many directions, like shoulders and hips. Pivot joints allow bones to rotate around each other, as seen in the neck. Saddle joints permit movement back and forth and side to side, such as in the thumb. Condyloid joints allow up and down and side to side movement without rotation, found in wrists and fingers. Gliding joints let bones slide over each other, found in wrists and ankles. These joints…

Changes of state refer to the physical transformations that matter undergoes when it changes from one state to another, such as between solid, liquid, and gas. These changes happen when matter absorbs or loses energy, usually in the form of heat, causing the particles to move more or less and rearrange themselves without changing the substance's chemical composition.

Key changes of state include:

• Melting: Solid to liquid (e.g., ice melting into water) when heat is added.

• Freezing: Liquid to solid (e.g., water freezing to ice) when heat is removed.

• Evaporation/Boiling: Liquid to gas (e.g., water boiling to steam) when more heat is added.

• Condensation: Gas to liquid (e.g., steam cooling to water droplets) when heat is removed.