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9/10/14. Begin Entry Ticket – silently and independently. How much is a $20 bill worth?. Does it matter if it is crumpled, old and/or dirty?. Extensive vs. Intensive Properties. Extensive properties – depends on the amount of matter in a sample. Example: Mass, Volume
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9/10/14 Begin Entry Ticket – silently and independently
How much is a $20 bill worth? • Does it matter if it is crumpled, old and/or dirty?
Extensive vs. Intensive Properties • Extensive properties – depends on the amount of matter in a sample. • Example: Mass, Volume • Intensive properties – depends on the type of matter • Example: Color, Temperature, Density • Why do all samples of a substance have the same intensive properties?
Identifying substances • Substance – matter that has a uniform and definite composition • Physical property – quality or condition of a substance that is observed without changing the composition. • We use physical properties to identify substances
Drinking Water ICE Steam • Molecules loosely packed; move slowly • Defined volume, no defined shape • Medium energy • Molecules spread far apart; move quickly • No defined volume or shape • High energy • Molecules tightly packed; vibrate • Defined shape and volume • Low energy
Drinking Water ICE Lower temperature Lower temperature Steam Freezing Condensation These are physical phase changes! Melting Vaporization Rising temperature Rising temperature • Molecules tightly packed; vibrate • Defined shape and volume • Low energy • Molecules loosely packed; move slowly • Defined volume, no defined shape • Medium energy • Molecules spread far apart; move quickly • No defined volume or shape • High energy
Physical Change – a property of a substance changes, but the composition remains the same. Ex: changing shape, size, phase Physical changes can be divided into two groups: irreversible and reversible Reversible – Can be easily “undone.” EX: folding paper, melting ice Irreversible – cannot be “undone.” cutting paper, cracking an egg
What if we had more than one substance? Mixtures!
Heterogeneous mixture – components are not distributed evenly • Homogenous mixture – components are not distributed evenly