Chemical and Physical Properties of Matter Science Survey Chemical and Physical Properties of Matter

Matter Matter is anything that has mass and takes up space. Chemistry is the study of matter and how it changes.

2Classifying Matter Pure substance (substance) – matter that always has exactly the same composition Ex. Table Salt, Table Sugar Every sample has the same properties due to a fixed, uniform composition.

Element – substance that contains only one type of atom, cannot be broken into simpler substances Atom – smallest particle of an element Ex. – Carbon, Oxygen, Nitrogen, Gold, Silver, Calcium, etc.

Matter: Compounds A substance made of atoms of more than one element bound together is a compound. Ex) water, NaCl Every compound is unique, and is different from the elements it contains. Elements and compounds are pure substances

Matter: Compounds, cont. The smallest unit of a compound that exhibits all of the properties of that substance is a molecule. Chemical formula- the chemical symbols and numbers indicating the atoms contained in a molecule of a substance

Mixtures – composition is not fixed, properties may vary Ex. Salsa, spaghetti sauce, sand, salad dressing, salt water Heterogeneous Mixtures – parts are noticeably different from one another Homogenous Mixtures – substances are so evenly distributed that it appears to contain only one substance

Heterogeneous Homogeneous

Solutions, Suspensions, Colloids Solution – formed when substances dissolve and for a homogeneous mixture; particles are too small to settle Suspension – heterogeneous mixture that separates into layers over time; larger particles Colloids – contain intermediate sized particles; do not separate into layers; particles scatter light

States of Matter solid - definite shape and volume, particles are close together in fixed positions. liquid - definite volume, indefinite shape. Particles are close together, but can still slide past each other. Liquids take the shape of their container. Viscosity is the resistance of a fluid to flow. For example, syrup is more viscous than water.

States of Matter, cont. gas - neither definite shape nor definite volume; particles are far apart. Gases are free to move in all directions. plasma- high temperature state of matter where atoms lose their electrons. Plasma is found in fluorescent bulbs, lightning, and stars. **The forces holding solids together are stronger than the forces holding liquids together. The forces holding gas particles together are the weakest.

Phase Model for Water

Kinetic Theory and States of Matter Energy of motion is kinetic energy. The kinetic theory says that all atoms are in motion. Increasing temperature causes particles to speed up. Decreasing temperature slows them down. At the same temperature, heavier particles move slower than lighter particles. Matter can change states if the movement of the molecules changes.

Changes of State Energy is the ability to change or move matter. Energy is needed for matter to change state, such as from a solid to liquid, or from liquid to gas. Endothermic processes require added energy, while exothermic process release energy to the environment. Evaporation is the change of a substance from a liquid to a gas. Condensation is the change of a gas to liquid form. Sublimation is the change of a solid directly to a gas.

Endothermic and Exothermic changes of State

Laws of Conservation Changing the state of matter does not change its composition or mass. Law of Conservation of Mass- Mass cannot be created or destroyed. Law of Conservation of Energy- Energy cannot be created or destroyed. Mass and energy can change forms. For example, when an ice cube melts, the mass of liquid water is the same as the mass of the ice cube.

Chemical properties Chemical property- the way a substance reacts with others to form a new substance with different properties. Examples: Gasoline is flammable.

Physical properties Physical property- a characteristic of a substance that can be observed or measured without changing the composition of the substance. Examples: shape, color, odor, texture, boiling point, density

Comparison of Chemical and Physical properties

Physical Properties Viscosity – a liquid’s resistance to flowing The greater the viscosity, the slower the liquid flows and vice versa Conductivity – a material’s ability to allow heat to flow Malleability – ability of a solid to be hammered without shattering

Physical properties: Definitions Boiling point- temperature at which a liquid becomes a gas below the surface. Water boils at 1000 C and freezes at 00 C. Freezing point- the temperature at which a liquid becomes a solid. Melting point- the temperature at which a solid becomes a liquid.

Chemical Changes Chemical changes occur when a substance changes composition by forming one or more new substances.

2.3 Chemical Properties Flammability – ability to burn in the presence of oxygen

Reactivity – how readily a substance combines chemically with other substances Ex. Rust forms when iron reacts with oxygen and water

Recognizing Chemical Changes Three types of evidence for chemical change Change in color Examples: Jewelry tarnishing Bananas turning black

Production of a Gas – bubbling, fizzing

Formation of a Precipitate Precipitate – solid that forms and separates from a liquid mixture

Physical Changes Physical change- A change in the physical form or properties of a substance that occurs without a change in the identity of the substance.

Physical changes, cont. Dissolving a substance in solution is a physical change, such as dissolving a solid in a liquid or a liquid in a liquid. Changes of state, such as melting, evaporating, boiling, condensing, and freezing are all physical changes.

Braiding hair is a reversible phys. change Cutting hair is a phys. Change that is not reversible