Properties of Materials

Chemical Properties how a material interacts with another material “social” behavior response to other matter (or lack of response) reactions

Chemical Properties Examples: burning reaction with acid reaction with water corrosion/rusting/oxidation others???? Burning – strike a match and burn a piece of paper – burn a piece of magnesium – “burn” a copper wire Drop a piece of zinc in HCl 3. Show clip of sodium in water????

Physical Properties characteristics it possesses by itself (in and of itself) “personal” traits response to energy

Physical Properties luster color density size magnetism texture odor viscosity crystalline structure color size texture melting point boiling point solubility http://cwx.prenhall.com/petrucci/medialib/media_portfolio/20.html - videos Demo – viscosity tubes Pyrite for luster

Physical Properties Electrical properties conductor or insulator Optical properties – response to light index of refraction – bending of light transparent – light passes through translucent – some light passes through but no distinct image opaque – no light passes through 1. Use a digital meter on a conductor and on an insulator 2. Index of refraction – how much light bends as it passes through a substance – example: standing in waist deep water or a pencil in a beaker of water, remind students of water gel crystals we did at beginning of year show examples of all 3 – use glass or plastic – show a Corelle plate http://webphysics.davidson.edu/faculty/dmb/EdibleOpticalMaterials/find_n_background.htm

Physical Properties Thermal properties – response to heat conductivity specific heat – how much energy it takes to change temperature thermal expansion – example: iron wire demo Conductivity – have them touch a table leg (wood) and a chair leg (metal) at the same time – discuss – use Ed. In. melt blocks Specific heat – metals have low – doesn’t take much energy to heat them up or cool them down – ceramics/glass are higher – water is very high (reason it is used in cooling systems) Ball and ring, bimetallic strip, piston and sleeve

Mechanical Properties subgroup of physical response to force or stress force – a push or pull stress – force causing a deformation or distortion (force per unit area)

Mechanical Properties Examples workability malleability – can be flattened ductility – can be drawn into wire (stretched), bent, or extruded Malleability - (show students a rolled penny) Ductility - (show drawn wire) Show Play doh fun factory for extrusion http://www.chem-pics.co.uk/animations.htm

Mechanical Properties Examples brittleness breaks instead of deforming when stress is applied hardness resistance to denting or scratching http://www.youtube.com/watch?v=i1x-vJ85sBA http://www.youtube.com/watch?v=eF5943tlbBs Brittleness – snap a piece of chalk Hardness - pass around talc (do a metal hardness test demo – dent metal plates using a heavy weight w/ a ball bearing attached – make a shading of the dents and measure their width w/ a caliper – rank the metals)

Mechanical Properties Examples elasticity ability to return to original shape after being deformed by stress rubber ball or piece of elastic http://www.flixxy.com/golf-ball-slow-motion.htm plasticity retains new shape after being deformed by stress wet clay ball or piece of saran wrap Show happy/sad balls Show poppers????

Mechanical Properties Examples toughness ability to absorb energy resistance to fracture http://www.steeluniversity.org/content/html/eng/charpy-test.asp http://www.youtube.com/watch?v=a_aOlh6dSA8 http://www.youtube.com/watch?v=N276_xjl04g&feature=related strength resistance to distortion by stress or force several types: tensile, compressive, torsional, bending, shear (toss a metal piece - scoopula, plastic water bottle, unglazed dried clay (in a baggie), a test tube (in a baggie), Corelle plate) – metals and polymers tend to exhibit more toughness than ceramics or glass – Corelle is an exception http://www.wmtr.com/Content/charpy.htm Excellent simulation - http://www.steeluniversity.org/content/html/eng/charpy-test.asp