Matter & Its Properties C 1.2

Matter Can be defined as anything that has mass & takes up space Mass is a measure of the amount of matter (using a balance) Volume is the amount of 3D space an object occupies

Basic Building Blocks of Matter Atoms are the smallest unit of an element that maintains the properties of that element An element is a pure substance made only of 1 kind of atom A compound is made from the atoms of 2 or more elements that are chemically bonded

Properties & changes in Matter Properties are characteristics that chemists use to help distinguish & separate substances Extensive properties depend on the amount of matter present (mass, volume, & amount of energy) Intensive properties do not depend on the amount of matter present (BP, MP, density, ability to conduct)

Physical Properties Physical properties are characteristics that can be observed or measured w/o changing the identity of the substance They describe the substance itself such as MP and BP

A change that does not involve a change in the identity of a substance Physical Changes A change that does not involve a change in the identity of a substance Grinding, cutting, melting, boiling Changes of state (L to G, S to L) Does not change the identity of a substance (ice is still H2O) Video – changes in matter

Solid has a definite shape & volume States of matter Solid has a definite shape & volume Particles are packed tightly together in relatively fixed positions Liquid has definite volume but indefinite shape Particles are close together but can move past each other

States of matter (cont.) Gas has neither definite shape/volume Particles move rapidly away from each other Plasma is a high temperature state in which atoms lose their electrons

Change of state does not affect the identity of the substance Changes of State Change of state does not affect the identity of the substance Melting Freezing Boiling

Chemical Properties Relates to a substance’s ability to undergo changes that transform it into different substances A new substance forms The ability to burn or rust

Chemical Change/Reaction A change in which 1 or more substances are converted into different substances Substances that react in a chemical change are the reactants Substances formed are the products Burning charcoal + oxygen -> CO2

Energy & Changes in Matter Energy is always involved when physical & chemical changes occur Energy can be light or heat Can be absorbed or released but energy is never created or destroyed (law of conservation)

Classification of matter Classified into 2 groups: Pure substances – can be an element or compound & composition is the same throughout Mixtures contain more than 1 substance & can vary in composition & properties

Mixtures A blend of 2 or more kinds of matter, each retaining its own identity & properties Parts are physically mixed together & can usually be separated Composition must be specified

Mixtures (cont.) Homogeneous mixtures are uniform in composition (same proportion of components throughout) – also called solutions Heterogeneous mixtures are not uniform throughout (can see the separate parts) Video – classifying matter

Has a fixed composition and every sample has: Pure substances Has a fixed composition and every sample has: the exact same chemical & physical properties Exactly the same composition Are either elements or compounds

Lab Chemicals & Purity Lab chemicals are treated as pure, but all chemicals have some impurities Table 1.1 lists grades of chemical purity

1a. Physical properties can be observed without changing the substance Section review 1a. Physical properties can be observed without changing the substance Physical – mass, volume Chemical – ability to burn

2 a. tearing paper – physical 2 b. melting wax – physical Section review 2 a. tearing paper – physical 2 b. melting wax – physical 2 c. burning a log – chemical 3. Decide if it has: definite shape/volume – solid definite volume/indefinite shape – liquid indefinite shape/volume – gas

Section review 3. Decide if it has: definite shape/volume – solid definite volume/indefinite shape – liquid indefinite shape/volume – gas

Section review 4. mixtures are made of more than one substance that are not chemically combined (retains its own properties), whereas pure substances have a definite, fixed chemical composition & has the same properties throughout