words to study for chem. test mass weight matter physical properties chemical properties...

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