Lauren ZurcherMrs. McCurdyScience 8-1 Chapter 2 Properties of Matter
2.1 Classifying Matter PURE SUBSTANCES: ◊ Matter that always has exactly the same composition ◊ Every sample of a given substance has the same properties because a substance has a ﬁxed, uniform composition
2.1 Classifying Matter ELEMENTS: ◊ A substance that cannot be broken down into simpler substances. ◊ An element has a ﬁxed composition because it contains only one type of atom.
2.1 Classifying Matter COMPOUNDS: ◊ A substance that is made from two or more simpler substances and can be broken down into those simpler substances ◊ Always contains two or more elements joined in a ﬁxed proportion
2.1 Classifying Matter MIXTURES: ◊ The properties of a mixture can vary because the composition of a mixture is not ﬁxed Heterogeneous Mixture: ◊ the parts of the mixture are noticeably different from one another EX: Salsa, Sand, Chocolate Chip Cookies Homogeneous Mixture: ◊ the substances are so evenly distributed that it is difﬁcult to distinguish one substance from another. EX: Salt Water, Lemonade, Milk
2.1 Classifying Matter SOLUTIONS, SUSPENSIONS, AND COLLOIDS ◊ Based on the size of its largest particles, a mixture can be classiﬁed as a solution, a suspension, or a colloid. Solution: when substances dissolve and form a homogeneous mixture. EX: windshield washer Suspension: a heterogeneous mixture that separates onto layers over time. EX: muddy water Colloid: contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension. EX: milk
2.2 Physical PropertiesViscosity — resistance to ﬂowing: Higher — slowerConductivity — to allow heat to ﬂowMalleability — to bend — to be hammered without shatteringHardness — toughness, hardnessMelting point — temp. which a substance goes from solid to liquidBoiling point — temp. which a substance boilsDensity — the purity of a substance — ratio: mass to its volume Physical properties are used to identify a material, to choose a material for a speciﬁc purpose, or to separate the substances in a mixture.
2.2 Physical Properties USING PROPERTIES TO SEPARATE MIXTURES◊ Filtration and distillation are two commonseparation methods.Filtration: separates materials based on the size of theirparticlesDistillation: separates substances in a solution based ontheir boiling points.
2.2 Physical Properties PHYSICAL CHANGES ◊ A physical change occurs when some of the properties of a material change, but the substances in the material remain the same. EX: sharpening a pencil, or cutting hair
Separation Techniques◊ Distillation: a process that separates the substances in asolution based on their boiling point.
Separation Techniques◊ Filtration: a process that separates materials based on thesize of particles and/or solubility.
Separation Techniques◊ Evaporation: a process used to isolate a solid dissolved in aliquid.property : solubilityEX: NaCl + Water (sodium chloride) table saltEvaporation DISCLAIMER: you will not be able to isolate pure samples of the liquid in the mixture.
2.3 Chemical Properties CHEMICAL PROPERTIES◊ A chemical property is any ability to produce a changein the composition of matter.◊ Chemical properties can be observed only when thesubstances in a sample of matter are changing into differentsubstances.
2.3 Chemical Properties CHEMICAL PROPERTIES ◊ Flammability is a material’s ability to burn in the presence of oxygen. ◊ Reactivity describes how readily a substance combines chemically with other substances.
2.3 Chemical Properties CHEMICAL CHANGE ◊ A chemical change occurs when a substance reacts and forms one or more new substances. ◊Three common types of evidence for chemical change are a change in color, the production of gas, and the formation of a precipitate.
2.3 Chemical Properties PRECIPITATE◊ A precipitate is any solid that forms and separates froma liquid mixture. ◊ When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same.