Words to Study for Chem. Test• Mass• Weight• Matter• Physical Properties• Chemical Properties• Characteristic Properties• Physical Changes• Chemical Changes• Signs of Chem. Change• States of Matter• Atoms
• Solid• Liquid• Gas/Gas Laws• Change of State• Melting/Melting Point• Boiling/Boiling Point• Freezing/Freezing Point• Evaporation• Condensation• Sublimation• Endo/Exothermic
Words to Study for Chem. Test• Solution• Solubility• Suspensions• Colloids• Pure Substance• Element• Compound• Mixture• Homogeneous Mixture• Heterogeneous Mixture
• Chemical Formulas• Chemical Equations• Reactants• Products• Subscripts• Coefficients• Law of Conservation of Mass• Decomposition Reaction• Replacement Reaction• Synthesis Reaction
Chemical Formulas• A combination of chemical symbols and
numbers to represent a substance• Examples– H20: Water
– CO2: Carbon Dioxide– NaCl: Salt– C6H1206: Sugar
Chemical Equations• A representation of a chemical reaction that
uses symbols to show the relationship between the reactants and the products
• ExamplesC + O2 CO2
2H2 + O2 2H2O
Reactants• A substance or molecule that participates in a
chemical reaction• Examples
C + O2 CO2
Reactants
2H2 + O2 2H2O
Reactants
Products• A substance that forms in a chemical reaction
• ExamplesC + O2 CO2
Product
Zn + 2HCl ZnCl2 + H2
Product
Subscripts• A number written below and to the right of a
chemical symbol in a formula• Tells how many atoms of that element are
present• Examples– CO2
– H20
– C6H12O6
Coefficients• A number that is placed in front of a chemical
symbol or formula• Tells how many molecules of that substance
are present• Keeps reaction balanced• Example 2H2 + O2 2H2O
Law of Conservation of Mass• Mass is neither created nor destroyed in
ordinary chemical and physical changes• Must start and end with the same amount• Example
Log + Fire Ashes + Smoke 30 kg 1 kg 28 kg 3 kg
Decomposition Reaction• A reaction in which a single compound
breaks down to form two or more simpler substances
• Example H2CO3 H2O + CO2
Replacement Reaction• A reaction in which one element takes the
place of another element in a compound• Example Zn + 2HCl ZnCl2 + H2
Synthesis Reaction• A reaction in which two or more substances
combine to form a new compound• Example 2Na + Cl2 2NaCl
Solution• A homogeneous mixture of 2 or more
substances evenly dispersed throughout a single phase
• Looks like one thing• Usually when 1 substance is dissolved in
another, but not always– Examples: Lemonade, Air, Bronze, Gatorade
Solubility• Ability of 1 substance to dissolve in another• To dissolve more quickly: Crush it, Stir it,
Heat it• Solute – the substance that is dissolved• Solvent – what substance is being dissolved
in– Example: Sugar dissolves in water
Suspensions• A mixture in which particles of a material are
more or less evenly dispersed throughout a liquid or gas
• When you shake it, it looks like one thing, but if you leave it setting, particles will settle to bottom– Example: Snow Globe
Colloids• Mixture consisting of tiny particles that are
intermediate in size between those in solutions and those in suspensions
• Particles aren’t so small that they completely dissolve like solutions, but aren’t so big they settle– These particles can scatter light– Example: Milk, Mayo, Deodorant
Homogeneous Mixture• Looks like or appears to be only 1 substance• Example– Gatorade– Lemonade
Heterogeneous Mixture• Looks like or appears to be more than 1
substance
Pure Substance• Sample of matter, either a single element or
a single compound, that has a definite chemical & physical properties
• Made of only 1 type of particle– Elements or Compounds
• Elements – made of atoms• Compounds – made of molecules
Element• A substance that can’t be separated or
broken down into simpler substances by chemical means
• Pure substance• Can’t be broken down at all• Made of one type of atom• Found listed on Periodic Table
Compound• Substance made up of atoms of 2 or more different
elements chemically combined with specific mass ratio
• Can only be separated by chemical changes• Made only of molecules– H20: Water– NaCl: Salt– C6H12O6: Sugar
– Fe2O3: Rust
• Properties of compound are completely different from the properties of elements that formed it
Mixture• Combination of 2 or more substances that are
not chemically combined• 2 or more things physically in the same place– Examples: Salad, Cereal, Pizza, Omelette
Change of State• Change of a substance from one physical
form to another• Requires adding or removing energy so that
particles can speed up or slow down
Endothermic• Energy is absorbed by a substance or
substances
Exothermic• Energy is released from a substance or
substances
Melting• Change of state when a solid becomes a
liquid• Particles must speed up• Add energy/heat• Endothermic
Melting Point• Temperature at which a substance melts• Water: 32°F or 0°C
Freezing• Change of state from a liquid to a solid• Particles must slow down• Remove energy/heat• Exothermic
Freezing Point• Temperature at which a substance freezes• Water: 32°F or 0°C
Evaporation• Change of a substance from a liquid to a gas
(only on surface)• Particles (on surface) must speed up• Add energy/heat• Endothermic
Boiling• Change of a liquid to a gas (throughout an
entire liquid)• Particles (on bottom of liquid) must speed up• Add energy/heat• Endothermic**Won’t happen unless air pressure equals
pressure in bubbles
Boiling Point• Temperature at which a substance boils• Water: 212°F or 100°C• At Sea Level: boiling depends on air pressure
Condensation• Change of state from a gas to a liquid• Particles must slow down• Remove energy/heat• Exothermic
Sublimation• Change of state from a solid to a gas– Example: Dry Ice
• Skips liquid stage• Add energy/heat• Endothermic
To Access the BBC Video:• In Internet Explorer, go to
www.tinyurl.com/christscience7• Click on Unit 2• Under Class Files/Links, click on
Behavior of Matter Test Bite (BBC)• When finished, turn in questions to
your period’s colored drawer
Atoms• Smallest unit of an element that maintains
the properties of that element• Can not be broken down into anything
smaller• Scientists used to think they couldn’t be split,
but we now know that was incorrect
States of Matter• The physical forms of matter, which include
solid, liquid, and gas
Solid• The state of matter in which the volume and
shape of a substance are fixed• Definite shape• Definite volume• Particles are tightly packed• Particles barely move– They vibrate in place
Liquid• The state of matter that has a definite
volume but not a definite shape• No definite shape• Definite volume• Particles move fast enough to separate a little– Allowing them to change shape
• Particles do not move fast enough to change volume
Liquid (Continued)• Viscosity: a liquid’s resistance to flow– High Viscosity: Slow Flow (Honey)– Low Viscosity: Fast Flow (Water)
• Surface Tension: force that attracts the molecules at the surface of a liquid to form the drop
Gas• The state of matter that does not have a
definite shape or volume• No definite shape• No definite volume• Particles move so fast that they completely
separate from each other– Allowing them to change shape and volume
Gas Laws• If Temperature remains Constant, Hallway– Volume Increases, Pressure Decreases– Volume Decreases, Pressure Increases– Inversely Proportional
• If Pressure remains Constant, Balloon– Temperature Increases, Volume Increases– Temperature Decreases, Volume Decreases– Directly Proportional
Physical Changes• A change of matter from one form to another without a
change in chemical properties• Usually reversible, no change to matter composition• End with the same thing you started with• Examples:
– Ripping– Crushing– Cutting– Heating– Cooling– Coloring– All changes of state
Chemical Changes• A change that occurs when one or more substances change
into entirely new substances with different properties • Never reversible• End with something different than you started with• Examples:
– Soured Milk– Burning– Digesting– Cooking/Baking– Rotting/Spoiling– Tarnishing
Signs of a Chemical Change• Change in color• Change in temperature• Fizzing/Foaming• Sound or light being given off• New smell• New taste• Precipitate – when two liquids are mixed together
and form a solid
Mass• A measure of the amount of matter in an object• Mass of an object is the same no matter where it
is located• Only way to change is to add or take away matter• Unit/Tool:– Grams (g)– Balance
Weight• A measure of the gravitational force exerted on
an object• Changes when the force of gravity changes– Differs on Earth & Mars
• Unit/Tool:– Newtons (N)– Spring Scale
Matter• Anything that has mass and takes up space• Made up of tiny particles called atoms– Atoms: smallest particle of matter
Physical Properties• Can be observed or measured without changing
the matter’s identity• Adjective – descriptive word• Examples– Color– Smell– Size/Shape– Texture/Taste– Temperature– Density– State (Solid, Liquid, Gas)
Chemical Properties• Substance ability to participate in chemical
reactions• Hard to observe• In order to see these you must change the
substance into a new substance• Examples– Flammability– Reactivity
Characteristic Properties• Chemical or physical property that is always the
same no matter what size the sample is• Can be physical or chemical• Most useful type of property• Examples– Density– Flammability– Reactivity– Boiling Point, Melting Point, Freezing Point– Color– Smell
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