2Physical Properties Physical Property : Characteristic of a material that can be observed or measured without changing the composition of the substances in the material.Examples:Viscosityconductivitymalleabilityhardnessmelting pointboiling pointdensity
3Examples of Physical Properties Viscosity –Tendency of a liquid to keep from flowingThick liquids high viscosity.Thin liquids low viscosity.
4Examples of Physical Properties Conductivity -Ability to allow heat or electricity to flowMaterials that have a high conductivity, such as metals, are called conductors.Good conductors of heat are usually also good conductors of electricity.
5Examples of Physical Properties Malleability -The ability of a solid to be hammered without shatteringMost metals, such as gold, are malleable.Solids that shatter when struck are brittle, not malleable.An ice cube or piece of glass breaks into small pieces when struck with a hammer.
6Examples of Physical Properties Hardness - resistance to scratchingOne material can scratch another material if it is harder than the other material.Examples:A kitchen knife can scratch a copper sheet because stainless steel is harder than copper.The material used to sharpen the knife blade must be harder than stainless steel.Diamond is the hardest known material.
7Examples of Physical Properties Melting and Boiling Points -Temperature at which material changes stateMelting point (freezing is same temperature)Melting solid to liquidFreezing liquid to solidBoiling point (condensing is same temperature)Boiling liquid to gasCondensing gas to liquid
8Examples of Physical Properties Density –the ratio of the mass of a substance to its volume (i.e. mass/volume)Characteristic PropertyDensity can be used to test the purity of a substance.Silver has a density of 10.5 g/cm3. A coin with a density of 9.9 g/cm3 is not made from silver, or it contains substances in addition to silver.
9Physical properties are used to: Examples of Physical PropertiesPhysical properties are used to:Identify materialsChoose materials for a specific purposeSeparate the substances in mixtures.
10Using Properties to Separate Mixtures Filtration and distillation are two common separation methods.Distillation – separates the substances in a solution based on their boiling points.Examples: gasoline, moonshine
11Recognizing Physical Changes Substances in the material remain the same.Some of the properties of a material change, properties such as: Size, Shape, State of matter (solid, liquid, or gas)Examples include:Water going from a liquid to a gas during boilingMelting butter in a panCrumpling a piece of paperSlicing a tomato
12Some but not all physical changes can be reversed. Braiding hair is a reversible change.Cutting hair cannot be reversed.Both are physical changes.
13Chemical PropertiesAs a candle burns, its compounds combine with oxygen in the air to form water and carbon dioxide.Chemical property –ability to produce a change in the composition of matter.Examples:FlammabilityReactivity
14Chemical Properties Flammability Reactivity A material’s ability to burn in the presence of oxygen.Materials that burn can be used as fuel.ReactivityHow readily a substance combines chemically with other substances
15Chemical ChangeRust forms when oxygen reacts with iron and water. Rust is a brittle, reddish-brown compound. Because iron is highly reactive, you would not choose iron to make jewelry or coins.
16Recognizing Chemical Change A chemical change occurs when a substance reacts and forms one or more new substances.Example:The color change in a banana peel is caused by chemical changes that are taking place in the cells of the banana.
17Recognizing Chemical Change 3 common types of evidence for a chemical change:Change in colorProduction of a gasFormation of a precipitate.
18Recognizing Chemical Change Change in Color – a clue that a chemical change may have produced at least one new substance.Examples:A shiny silver bracelet that is exposed to air will darken.As a match burns, it shrivels up and turns black.A new copper roof and an old copper roof have different colors.
19Recognizing Chemical Change A new copper roof has a reddish color.The green patina on an old copper roof is a mixture of copper compounds.
20Recognizing Chemical Change Production of a GasVinegar + Baking Soda bubbles of carbon dioxide form immediately.A similar chemical change happens when you use baking powder as an ingredient in a cake recipe.Bubbles of carbon dioxide expand and cause the cake to rise.
21Recognizing Chemical Change Formation of a PrecipitatePrecipitate – any solid that forms and separates from a liquid mixture.Example:When an acid is added to milk, proteins in the milk undergo a chemical change that causes them to stick together in clumps and form a precipitate cottage cheese.
22Chemical ChangesColor change, a gas, or a precipitate DO NOT guarantee that a chemical change has taken place.When an iron horseshoe is heated, its color changes from gray to red, but the iron is still iron. That means the change is physical, not chemical.
23Chemical Changes Chemical change: composition of the matter changes. Are different substances present after a change takes place? If not, then the change is physical, not chemical.Chemical change: composition of the matter changes.You got something NEWPhysical change: composition of the matter stays same.