1.2 properties and changes of matter 4 states of matter - solid, liquid, gas, 4 th state – plasma
Post on 02-Jan-2016
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What are Physical Properties?
•Physical properties – characteristic of matter that does not change example: melting point, color, density, state of matter (solid, liquid or gas).
Density - the amount of matter (mass) compared to the amount of space (volume) the object occupies
•Density is a physical property of matter that expresses a relationship of mass to volume. •The more mass an object contains in a given space, the more dense it is.•It’s a constant for that substance (a number that does not change)
Example: Density of Gold = 19.30 g / cm3
Question: If you cut a brick of gold in half would the Density still be 19.30 g/cm3?
Yes…. Why?
Ratio: cut mass in half – you are also cutting the volume in half
Formula:
Density = mass/volume D = m / V
•The unit for mass is grams (g) or (kg), and the unit for volume is mL or cm3 usually,
So, the units for Density are g/mL, or g/cm3
Common DensitiesDensity of water is 1.00 g/mlThe density of a material varies with temperature Usually, if temperature increases – Density decreases.Exception: Ice
Physical Properties of Matter:
1) State of matter (solid, liquid or a gas)2) Density (D = M/V)3) Malleability - ability to bend4) Ductile – ability to be drawn out into thin wires5) Melting point, boiling point, texture, color, odor
Physical Change – a change in matter that does not change the identity of individual substance.
Phase Changes are Physical Changes
Example: ice melting to water - Substance is still H2O
Clues for Physical Changes:
1) Change in shape – dissolving, cutting in half2) Phase changes – liquid to gas, melting etc
Chemical Properties and Changes
•Chemical properties –are characteristics of a material that become evident when the material undergoes a chemical reaction or chemical change. •Chemical Change - is any change that results in the formation of new chemical substances.
•Chemical Reactions describe how a substances change into other new substances.
Ex: rusting of iron, leaves changing color, burning flame, combustion of gasoline in a car engine.
Chemical Properties
1) Ability to support burning – Oxygen gas
In a Chemical Change, Matter is neither created nor destroyed:
“Law of conservation of mass and energy”
2 Mg + O2 ---- 2 MgO
Clues Chemical Changes:
1) Bubbles – gas forming 2) Color Changes3) Heat changes – warm or cold
Chemical changes involve a change in energyEnergy = ability to do work Energy is either added or taken away.
Exothermic Reaction a reaction that releases energy (heat energy).
‘Exo’ – out; ‘thermic’ - heat•The container in which an exothermic reaction is taking place will feel hot.
Endothermic Reaction – reaction that takes in energy or (heat).
Endo = “into” - The container will feel cold.
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