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 Examples C + O2  CO2 2H2 + O2  2H2O

Reactants A substance or molecule that participates in a chemical reaction Examples C + O2  CO2 Reactants 2H2 + O2  2H2O

Products A substance that forms in a chemical reaction Examples C + O2  CO2 Product Zn + 2HCl  ZnCl2 + H2

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 Skips liquid stage 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