Matter and Change Test II Unit 2 Matter and Change Test II

Obj. 11-13…Separation of Matter Elements are the purest substances on earth…they cannot be broken down any further. Compounds are formed by chemically bonding two or more elements together. ~ must be chemically separated (reactions). Mixtures are formed by physically combining two or more pure substances together. ~ can be physically separated. Mixtures are separated by their physical properties. ~ boiling point, density, solubility etc…

Obj. 11-13 cont… How could you separate a mixture of sand and salt? ~ dissolve salt in water and filter out the sand. ** separation based on solubility! How could you separate a mix of iodine and iron filings? ~ use a magnet to pull out the iron filings. ** separation based on magnetism!

Obj. 11-13 cont… Four methods of separation of mixtures… Distillation… Ex…mixture of alcohol (BP = 78.5°C) and water (BP = 100°C) separates a mixture of liquids based on different boiling points.

Obj. 11-13 cont… Filtration… Ex…a sand and salt mixture separates two solids based on their solubility (ability to dissolve) in different solvents.

Obj. 11-13 cont… Centrifugation… separates substances based on the density of the particles in the mixture. Ex…blood components, proteins in milk, precipitate in a liquid

Obj. 11-13 cont… Chromatography… Ex… pigments in ink, pigments in chlorophyll separates based on the absorption of the substances in the mixture.

Obj. 14…Physical vs. Chemical Properties Physical properties…can be observed w/out changing the substance. Ex… ~ color ~ density ~ texture ~ size ~ boiling/melting point ~ solubility ~ magnetism

Obj. 14 cont… Chemical properties…properties that explain how a substance will react or behave. Ex… ~ reactivity to…  water  acids  bases ~ flammability ~ ability to be oxidized (lose e-)

Obj. 15…Physical vs. Chemical Changes Physical changes…changes in appearance only…NOT chemical make-up. Evidence of physical changes... ~ color change (if same substance) ~ change in shape ~ change in temp. (manually heating and cooling) ~ change in size ~ change in phase

Obj. 15 cont… Examples of physical changes... ~ breaking a window ~ tearing / cutting a piece of paper ~ melting a piece of ice

Obj. 15 cont… Chemical changes…changes result in a re-arrangement or recombination of atoms (NEW substance!). ~ can’t get original substance back w/out chem. rxn. Evidence of chemical changes... ~ gas / bubbles given off ~ formation of precipitate ~ heat given off / absorbed (breaking/making chem. bonds) ~ light given off ~ color change (if new substance)

Obj. 15 cont… Examples of chemical changes... ~ silver tarnishing ~ a nail rusting ~ burning a match ~ food rotting/souring ~ baking bread

Obj. 16…Law of Conservation of Mass ‘matter cannot be created or destroyed’ total mass on reactant side MUST = mass on product side. ~ ‘what goes into the rxn. must come out!’ Ex… A + B C + D 5 grams 8 grams 2 grams _________ 11 grams 13 grams

Obj. 17-18…Density Density…amount of matter present in a given volume. ~ how heavy a substance is D = m/v units = g/ml or g/cm3

Obj. 17-18 cont… Density problems… 1. A nail has a vol. of 0.880 cm3 and a mass of 6.920 grams. What is the density of the nail? D = m/v D = 6.920 g / 0.880 cm3 D = 7.86 g/cm3 2. Vegetable oil has a density of 0.916 g/ml. Calculate the mass of 500.0 ml of oil. m = D(v) m = 0.916 g/ml (500.0 ml) m = 458 grams 3. The density of a piece of wood is 0.86 g/cm3. What is the volume of the wood if its mass is 75 grams? v = m/D v = 75 g ÷ 0.86 g/cm3 v = 87 cm3

Obj. 17-18 cont… To calculate density of an object… ~ find mass of object using balance ~ find vol. of object by using the water displacement method ** water displacement will not work if solid dissolves or floats in water.