Properties and Changes Section 3.1 Properties of Matter Properties and Changes Section 3.1

What is Matter? Matter = Substance: matter that has a uniform and unchanging composition, aka pure substance Mixture: two or more substances that have been combined and each substance retains its own chemical identity (sugar + flour) Pure Substances Impure Substance (mixture) distilled water ocean = water + salt

Physical Properties Substance – matter that has a uniform and unchanging composition Example: salt – NaCl Physical properties – characteristics that can be observed or measured without changing the composition of the sample viscosity hardness density conductivity melting point color malleability boiling point odor

2 Types of Physical Properties Extensive properties – dependent on the amount of substance present Intensive properties – independent of the amount of substance present

Recognizing Physical Changes Some of the properties of a material change, but the substances in the material remain the same; chemical composition remains the same; some are reversible heating butter crumpling paper slicing a tomato wrinkly shirt/iron hair braiding peeling oranges Change of state Ice-melting  liquid

Physical Separation of Substances magnetic properties crystallization/evaporation filtration chromatography distillation manual separation

Phases of Matter Materials can be classified as solids, liquids, gases, or plasma based on whether their shapes and volumes are definite or variable Shape and volume are clues to how the particles within a material are arranged

Solids Definite shape and volume Atoms are packed close together and have an orderly arrangement of particles Changing the container doesn’t change the shape or volume of a solid Examples: pencil, cafeteria tray, book, quarter

Liquids Definite volume and take the shape of its container Can be poured, will take on a new shape Atoms are close together, but their arrangement is more random than those of a solid Examples: juice, water, mercury, honey

Gases Does not have a definite shape nor a definite volume Takes the shape and volume of its container Atoms are not arranged in a regular pattern and can have a big space between them COMPRESSIBLE Examples: Air, helium, natural gas

Plasma Ionized gas with enough energy to have free electrons lightning sun neon signs

Kinetic Energy of Phases of Matter plasma gas liquid solid

Very close together, orderly arrangement Fixed No Particles Shape Volume Compressible? Solid Very close together, orderly arrangement Fixed No Liquid Close together but not as orderly as solid Changes Gas Lots of space between, no order Yes

Chemical Properties Chemical properties – the ability of a substance to combine with or change into another substance Iron + O2 -> Rust (FeO) Burning Cooking CO2 + H2O -> C6H12O6 + O2 EVERY SUBSTANCE HAS A UNIQUE SET OF PHYSICAL AND CHEMICAL PROPERTIES

Chemical Equations A useful description of a chemical reaction tells you the substances present before and after the reaction Reactants undergo the change and the new substances that are formed are the products Reactants Products

Recognizing Chemical Changes Evidence of chemical changes include: Change in color – leaves on trees, banana peel, copper, silver Production of gas (bubbles) – vinegar and baking soda, cake baking Formation of a precipitant – acid + milk (protein goes through chemical change), cottage cheese Production of light Temperature Change – reaction causes heat to be given off or absorbed (gets cold) Endothermic Exothermic

Law of Conservation of Mass Mass is neither created nor destroyed Mass reactants = Mass products Reactants  Products H2O + O2 H2O 18 grams + 22 grams  ? H2O

Steps to Solve Law of Conservation of Mass Problems Write what you know chemical reaction reactants and their masses products and their masses What are you solving for? Solve for your unknown

Practice! From a laboratory experiment designed to separate water into hydrogen and oxygen gas, a student collected 10.0 g of hydrogen and 79.4 g of oxygen. How much water was initially involved in the process? Chemical Reaction H2O  H2 + O2 Reactants  Products Law of Conservation of Mass says… Mass reactants = Mass of Products H2O mass = H2 mass + O2 mass H2O mass = 10.0 g + 79.4 g H2O mass = 89.4 g What do we know? H2 = 10.0 g O2 = 79.4 g What is our unknown? H2O = ??? g

More Practice! A student carefully placed 15.6 g of sodium in a reactor supplied with an excess quantity of chlorine gas. When the reaction was complete, the student obtained 39.7 g of sodium chloride. How many grams of chlorine gas reacted? Chemical Reaction Reactants  Products Sodium + Chlorine  Sodium Chloride Law of Conservation of Mass says… Mass reactants = Mass of Products Sodium mass + Chlorine mass = Sodium Chloride mass 15.6 grams + ? grams = 39.7 grams ? grams = 24.1 grams of Chlorine What do we know? Sodium = 15.6 g Sodium Chloride = 39.7 g What is our unknown? Chlorine = ??? g

Practice! Law of Conservation of Mass says… In a flask, 10.3 g of aluminum reacted with 100 g of liquid bromine to form aluminum bromide. After the reaction, no aluminum remained, and 8.5 grams of bromine remained unreacted. How many grams of compound were formed? Law of Conservation of Mass says… Mass reactants = Mass of Products Aluminum used+ Bromine used = Aluminum Bromide made 10.3 grams + 91.5 grams = ??? grams 101. 8 grams = ? Grams of Aluminum Bromide Chemical Reaction Reactants  Products Aluminum + Bromine  Aluminum Bromide What do we know? Aluminum = 10.3 g Bromine = 100 g Bromine left over = 8.5 g Bromine used = ?? = 100 – 8.5 g = 91.5 g What is our unknown? Aluminum Bromide = ??? g

Practice! A 10.0 g sample of magnesium reacts with oxygen to form 16.6 g of magnesium oxide. How many grams of oxygen reacted? If 50 grams of sodium reacts with chlorine to form 126 grams of salt, how many grams of chlorine reacted? If 20 grams of aluminum reacts with 200 grams of bromide to form aluminum bromide, and no aluminum is left after the reaction, but 23 grams of bromine remained unreacted how many grams of aluminum bromide were formed?

Practice! If 178.8 g of water is separated into hydrogen and oxygen gas, and the hydrogen gas has a mass of 20.0 g what is the mass of the oxygen gas produced? From a laboratory process, a student collects 28.0 g of hydrogen and 224.0 g of oxygen. How much water was originally involved in the process?

Practice! 9. A student carefully placed 23.0 g of sodium in a reactor with an excess quantity of chlorine gas. When the reaction is complete, the student obtained 58 grams of salt. How many grams of chlorine reacted? 10. A 10 gram sample of iron reacts with oxygen to form 18.2 grams of ferric oxide. How many grams of oxygen reacted?