CHAPTER 2

How to classify?

CLASSIFYING MATTER MATTER PURE SUBSTANCE MIXTURE ELEMENTCOMPOUND HOMOGENEOUSHETEROGENEOUS

definitions Pure Substance: – MATTER THAT ALWAYS HAS THE SAME COMPOSITION Mixture: – A PHYSICAL COMBINATION OF 2 OR MORE SUBSTANCES

more definitions Two categories of Pure Substances: Element – Can’t be broken down into simpler substances – Organized on Periodic Table – Each contain different types of atom – Amazing: Only about 110 different atoms make

Elements some more

Compound Can be broken down only by chemical reaction Examples: H 2 O SiO 2 C 6 H 12 O 6 Proportions are FIXED – All water everywhere forever has 2 H and 1 O Properties of Compound are DIFFERENT from the elements it’s made from Na + Cl 2  NaCl Can be broken down only by chemical reaction Examples: H 2 O SiO 2 C 6 H 12 O 6 Proportions are FIXED – All water everywhere forever has 2 H and 1 O Properties of Compound are DIFFERENT from the elements it’s made from Na + Cl 2  NaCl

Mixtures Definition: 2 or more substances physically combined Examples: fruit salad, salt water, steel, sand, striped cloth, maple syrup Keep some (most) of their individual properties. Classified by how well the substances are mixed.

Heterogeneous Mixture The parts are noticeably different from one another. fruit salad, sand, striped cloth

Homogeneous Mixture The parts are so evenly mixed the individual parts are difficult or impossible to distinguish. Sea water, steel, maple syrup

Special Types of Mixtures 1.SOLUTION Formed when one substance DISSOLVES in another Kool-Aid, Antifreeze, Oxygen in water Dissolved particles are so small: – Do not separate over time – If filtered, no particles are trapped – Light will pass through without being scattered

2. SUSPENSION A heterogeneous mixture that will separate over time. Muddy water, OJ with pulp, Apple cider Dissolved particles are larger: – Will separate over time – If filtered, particles will be trapped – Light passing into it is scattered in all directions

3. COLLOID A mixture with larger particles than solution but smaller than suspension Fog, milk, styrofoam, blood, gelatin Medium-sized particles – Will not separate into layers – A filter traps no particles – Will scatter light in all directions

CHECK YOURSELF Place the following in order from smallest to largest particle size SUSPENSION, SOLUTION, COLLOID SOLUTION COLLOID SUSPENSION SMALLEST LARGEST

Fill in the diagram MATTER MIXTURE PURE SUBSTANCE ELEMENTCOMPOUND HOMOGENEOUSHETEROGENEOUS SOLUTION COLLOID SUSPENSION

Physical Properties Any characteristic that can be measured or observed without changing the composition of the material.

VISCOSITY – Ability to flow…slow flowing (syrup) = viscous CONDUCTIVITY – Ability to conduct heat and/or electricity MALLEABILITY – Ability to bend or be hammered without breaking HARDNESS – Measures resistance to shape change

Melting Point – Temp at which particles become free to pass each other Boiling Point – Temp at which particles gain total freedom from one another Density – Amount of matter per unit volume

Uses of Physical Properties 1.Identify a substance:  List of properties is like a fingerprint 2.Choosing a substance: – Bulletproof vest? – Artificial Heart?

3. Mixture Separation – Filtration Uses differences in particle size – Distillation Uses differences in boiling point

Divide this list into two groups: Burning a marshmallow Cutting paper Melting an ice cube Smashing a light bulb Rusting car Dissolving salt in water Baking soda + Vinegar Dissolving salt in water Cutting paper Melting an ice cube Smashing a light bulb Burning a marshmallow Rusting car Baking soda + Vinegar

Chemical Properties Can be observed only when the substance is changing into a different substance Burning a marshmallow Rusting car Baking soda + Vinegar

Two Names: 1.Flammability – Ability to burn in the presence of oxygen 2.Reactivity – describes how readily a substance combines chemically with another Sodium is reactive with water Iron is not reactive with water Magnesium is reactive with acid

Recognizing Chemical Change Color Change – Copper turns green with age – Rust Form a Gas – Baking soda + Vinegar – Magnesium + Acid Form a Precipitate – lead nitrate + sodium iodide

Practice with P/C Changes Shattering GlassP C SunburnPC Bleaching clothesPC Baking cookiesPC Folding laundryPC Ripping your pantsPC Hydrogen peroxide on a cutPC