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Properties of Matter. (characteristics ; descriptions of matter) Physical Properties - can be observed and measured without changing the material’s composition. Examples- color, hardness, m.p ., b.p .
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Properties of Matter (characteristics ; descriptions of matter) • Physical Properties- can be observed and measured without changing the material’s composition. • Examples- color, hardness, m.p., b.p. • Chemical Properties- can only be observed by changing the composition of the material. • Examples- combustibility, bio-degradability, reactivity/inertness etc.
Describing Matter • Properties can also be classified as: • Extensive/Extrinsic– depends on the amount of matter in the sample (Mass, volume) • Intensive/Intrinsic– depends on the type of matter, not the amount present (Density, Boiling Point, Melting Point)
Physical vs. Chemical Change • Physical change will change the visible appearance, without changing the composition of the material. • Boiling, melting, cutting, bending, freezing • Chemical change– involves a change in composition (new substances are formed) • Rusting, burning, decomposition
Recognizing Chemical Changes • Energy is absorbed or released • Color changes • Gas production (bubbling, fizzing, or odor change; smoke) • formation of aprecipitate- a solid that separates from solution
Separating Mixtures Some mixtures can be easily separated by physical means: • Sorting - rocks and marbles • Use of magnet - iron filings and sulfur • Filtration- separates a solid from the liquid
Components of dyes such as ink may be separated bypaper chromatography. Separation of a Mixture
Separation of a Mixture Distillation:takes advantage of different boiling points. NaCl boils at 1415 oC
Matter can be classified as: Mixtures – can be separated by physical means Substances – cannot be separated by physical means
Mixtures are a physical blend of at least two substances; have variable composition. They can be either: • Heterogeneous – the mixture is not uniform in composition • Chocolate chip cookie, gravel, soil. • Homogeneous - same composition throughout; called “solutions” • Kool-aid, air, salt water • Every part keeps it’s own properties.
Phase? • The term “phase” is used to describe any part of a sample with uniform composition of properties. • A homogeneous mixture consists of a single phase • A heterogeneous mixture consists of two or more phases.
Substances are either: a) elements, or b) compounds
Substances: element or compound • Elements- simplest kind of matter • cannot be broken down any simpler substances that still have the properties of that element! • all one kind of atom. • Compounds are substances that can be broken down into simpler substances onlyby chemical means • made of two or morekinds of atoms, chemically combined (not just a physical blend!)
Symbols & Formulas • Elements – represented by a symbol (1 or two letters) B, Ba, C, Ca, He • Compounds – represented by a formula. NaCl, CO
Made of one kind of material Made of more than one kind of material Atoms are chemi- cally bonded It’s just a physical blend Definite composition Variable composition Compound vs. Mixture Compound Mixture
Element Compound Mixture Which is it?