Chapter 15: Classification of matter

Composition of Matter Matter can exist as: Substance: Type of matter with a fixed composition; can be element or compound; Ex: He, water, salt Element: Substance made up of atoms that are all alike; cannot be broken down into any other substance Ex: graphite in pencil point Compound: Substance in which the atoms of 2 or more elements are chemically combined in a fixed proportion Ex: water, CO2 Mixture: Matter composed of two or more substances that can be separated by physical means

mixtures Heterogeneous Mixture: Mixture in which different materials remain distinct Ex: Salad, oil and vinegar dressing Suspension: A heterogeneous mixture made of a liquid and solid particles that settle Ex: River deltas, seasoning in salad dressing Colloids: A heterogeneous mixture with particles that never settle Ex: milk (water, fats, proteins), fog (liquid suspended in air) Note: you can identify a colloid by shining a light through it; light beam is invisible as it passes through a solution, but it can be seen as it passes through a colloid; This scattering of light through a colloid is called the Tyndall Effect

Mixtures Homogeneous Mixture: A mixture that remains constantly and uniformly mixed and has particles that are so small that they cannot be seen with a microscope; solution is same thing as a solution Ex: tea, vinegar

Properties of matter: PhysicAl Physical Property: Any characteristic that you can observe without changing the identity of a substance Ex: color, shape, size, density, melting point, boiling point, viscosity, solubility, malleability, conductivity, melting point, boiling point, solubility Distillation: Process of separating substances in a mixture by evaporating a liquid and recondensing its vapor Ex: separate 2 liquids with different boiling points

Properties of matter: chemical Chemical Property: Any characteristic of a material that you can observe that produces one or more new substances,;describe the ability of a substance to change into another substance Ex: flammability and reactivity

Physical and chemical changes PHYSICAL CHANGES IN MATTER Physical changes only change physical properties of a substance Does not produce a new substance Phase changes are physical Ex: breaking, bending, melting, freezing, tearing, dissolving

Physical and chemical changes CHEMICAL CHANGES IN MATTER The process by which a substance changes into another substance Does not produce a new substance Also called chemical reactions Ex: Burning, rusting, baking soda and vinegar

Law of Conservation of Mass: total mass of the reactants = total mass of the products