Chem Y10 U1 - Matter

• Matter is anything that occupies space and has mass.
• The law of conservation of mass states that in a closed system, the total mass of the reactants must equal that of the products. Therefore, mass cannot be created or destroyed; it can only be transformed from one form to another.
• Atoms are the smallest particles that can exist as an element and cannot be broken down into simpler substances by chemical means.
• Elements are pure substances composed of only one type of atom. Each element has a unique atomic number, which determines the number of protons in its nucleus.
• A molecule is a group of two or more atoms held together by covalent bonds.
• Compounds are formed when two or more elements chemically combine with each other. Compound molecules contain atoms of different elements bonded together.
• A mixture is made up of two or more components that have not been combined chemically. The properties of mixtures depend on their composition.
• Pure substances are composed of only one type of molecule or atom. They have a fixed and uniform composition, meaning their properties are consistent throughout.
• Impure substances, also known as mixtures, are composed of two or more different substances physically combined. Their composition can vary, and their properties may not be uniform throughout.
• The formula for density is mass/volume.
• In solids, particles are tightly packed together and vibrate in fixed positions. They have a definite shape and volume and are not easily compressible.
• In liquids, particles are less tightly packed than in solids and can move around more freely. They have a definite volume but no fixed shape and can be poured or compressed.
• In gases, particles are far apart and move around randomly at high speeds. They have no definite shape or volume and can be easily compressed.
• The STP and gas volume are directly proportional; if you double the number of moles of gas, the volume doubles.
• By supplying heat energy to matter, we increase its kinetic energy to convert solids to liquids and liquids to gases.
• The kinetic theory of matter explains the behavior of matter based on the idea that it is composed of tiny particles in constant motion. These particles can be atoms, molecules, or ions, and their movement determines the state of matter.
• Translational: This type of motion describes the movement of a particle from one point to another in a straight line. Imagine a car driving down a highway; that's translational motion. The particle's position changes, but its orientation and internal structure remain the same.
• Rotational: Rotational motion occurs when an object spins about an axis. Think of a spinning top or a rotating wheel. In this case, the particle's position remains unchanged, but its orientation does not.
• Vibrational: In this type of motion, the particle oscillates back and forth around a fixed equilibrium position, like a bouncing ball or a vibrating guitar string. The particle's position and orientation remain constant, but its internal energy changes.
• Diffusion is a physical process where molecules move from a region of high concentration to a lower concentration. This movement is driven by random molecular motion and the tendency for particles to spread out evenly in the available space.
• The movement of particles increases with increasing temperature. This is because higher temperatures provide more kinetic energy to the particles, causing them to move faster and collide more frequently.
• Increasing pressure also leads to increased particle movement. This is because the particles are confined to a smaller space, resulting in more frequent collisions and greater overall movement.
• Their concentration influences the movement of particles. In areas of higher concentration, particles are closer together and collide more often, leading to increased movement. This is particularly relevant in diffusion, where particles move from areas of high concentration to areas of low concentration.
• The rate of diffusion is inversely proportional to the square root of the molecular mass of the diffusing substance. This means that lighter molecules diffuse faster than heavier molecules. This relationship is known as Graham's Law of Diffusion. This can be explained by the kinetic theory of gases. Lighter molecules have higher average velocities than heavier molecules at the same temperature. This higher velocity allows them to move and spread out more quickly.
• Meniscus: The curved surface of a liquid in a graduated cylinder or other container, caused by the liquid's surface tension and adhesion to the container's walls. When reading the volume, always measure from the bottom of the meniscus for consistent and accurate results.
• Parallax Error: The apparent shift in the position of an object when viewed from different angles. To avoid parallax error, ensure your eye is level with the bottom of the meniscus when taking the reading.