2.1 Matter has observable properties Chapter 2: Properties of Matter 2.1: Matter has observable properties 2.2: Changes of state are physical changes 2.3: Properties are used to identify substances 2.1 Matter has observable properties Have learned… Matter has mass and volume Matter is made of atoms Matter exists in different substances Will learn… Physical and chemical properties Physical changes Chemical changes

Physical Properties Examples? Color, shape, size, texture, volume, mass Take a piece of clay or play-doh What physical properties change? Shape changed, color/texture/mass/volume stay same Is it still play-doh?

Physical Properties Play-doh: did the density stay the same? Mass = 200 g, Volume = 100 cm3 = 100 mL Density = Mass/Volume = 2 g/ cm3 Break mass in half: 100 g & 100 g Volume? 50 mL & 50 mL New total mass, volume, density? 200 g, 100 mL, 2 g/cm3 200g/100mL = 2 g/cm3 ; 100g/50mL = 2 g/cm3

Density For any substance, the amount of mass in a “unit” of volume is constant Does density change after a state (of matter) change? If density = 6 g/cm3 and volume = 12 cm3, what is the mass of the object?

Physical Changes Is breaking off a piece of clay a physical change or a chemical change? No change in the physical property of the substance itself – still clay Liquid water to ice? Still H2O

Physical Changes Book: Sheep – sheering spinning dyeing – all physical changes – Original substance remains the same.

Chemical Changes Wood burning to ashes – new substance New substance released into the air Chemical Properties – combustibility, ability to rust, tarnish (Statue of Liberty – copper changes to blue-green when exposed to air)

Chemical Changes Substance is affected Combination of atoms are rearranged to form a new substance Ex: Iron plus oxygen = rust! 4Fe(s) + 3O2(g) --> 2Fe2O3(s) Ex: Antacid in water Ex: Cooking an egg (and digestion) **True indication of a chemical change? A new substance has been formed

Signs of a Chemical Change (Can you see them all?) Production of an odor – egg rotting (sulfer) Change in temperature – burning log Change in color – fruit ripening Formation of bubbles - antacid Formation of a solid – two liquid combined to form a solid – calcium carbonate precipitates in shells Ca+2(aq)+2HCO3-(aq)↔CaCO3(s)+CO2 (g)+ H2O(l) http://www.classzone.com/books/ml_sci_ca8/page_build.cfm?id=resour_ch1&u=2#%23