Chemical Properties & Physical and Chemical Changes

Physical changes are those changes that do not result in the production of a new substance.  If you melt a block of ice, you still have H2O at the end of the change.   

If you break a bottle, you still have glass If you break a bottle, you still have glass.  Painting your nails will not stop them from being fingernails.  Some common examples of physical changes are: melting, freezing, condensing, breaking, crushing, cutting, and bending.

Some, but not all physical changes can be reversed Some, but not all physical changes can be reversed. You could refreeze the water into ice, but you cannot put your hair back together if you don’t like your haircut!

Special types of physical changes where any object changes state, such as when water freezes or evaporates, are sometimes called change of state operations.

CHEMICAL PROPERTIES Chemical properties can ONLY be observed AS the substances are changing into different substances.

Chemical changes, or chemical reactions, are changes that result in the production of another substance. 

FLAMMABILITY: A material’s ability to BURN in the presence of OXYGEN

REACTIVITY: How readily (easily) a substance combines chemically with other substances.

Which has higher reactivity Which has higher reactivity? A 14 karat gold ring or a cheap metal ring from the vending machine at the grocery store? What is your evidence?

When you burn a log in a fireplace, you are carrying out a chemical reaction that releases carbon.  When you light your Bunsen burner in lab, you are carrying out a chemical reaction that produces water and carbon dioxide. 

Common examples of chemical changes that you may be somewhat familiar with are; digestion, respiration, photosynthesis, burning, and decomposition. 

Physical or Chemical Change? Painting Wood PHYSICAL

Physical or Chemical Change? Burning Paper CHEMICAL

Physical or Chemical Change? Digestion of food CHEMICAL

Sugar dissolving in water PHYSICAL Physical or Chemical Change? Sugar dissolving in water PHYSICAL

Iron turning red when heated PHYSICAL Physical or Chemical Change? Iron turning red when heated PHYSICAL

Physical or Chemical Change? Evaporation PHYSICAL

A pond freezing in winter PHYSICAL Physical or Chemical Change? A pond freezing in winter PHYSICAL

Physical or Chemical Change? Melting ice PHYSICAL

Physical or Chemical Change? Cutting wire PHYSICAL

Physical or Chemical Change? Painting fingernails PHYSICAL

Physical or Chemical Change? Cutting fabric PHYSICAL

Physical or Chemical Change? Baking muffins CHEMICAL

Physical or Chemical Change? Shattering glass PHYSICAL

Decomposition of old leaves CHEMICAL Physical or Chemical Change? Decomposition of old leaves CHEMICAL

Physical or Chemical Change? Wrinkling a shirt PHYSICAL

Physical or Chemical Change? An old nail rusting CHEMICAL

characteristics that can be observed or measured PHYSICAL Properties characteristics that can be observed or measured without changing the composition Ex. Breaking a glass, dying your hair Color, density, odor, taste, melting, freezing & boiling point, magnetism, solubility

Some, but not all physical changes can be reversed Some, but not all physical changes can be reversed. You could refreeze the water into ice, but you cannot put your hair back together if you don’t like your haircut!

Classify each statement as physical or chemical property/change. Pure metals have a higher luster (are shiny and reflect light). The surfaces of some metals become dull when exposed to air. Nitrogen gas, a relatively nonreactive material at room temperature, can form nitrogen oxides at the high temperatures of an operating automobile engine. Milk turns sour if left too long at room temperature. Diamonds are hard enough to be used as a coating for drill bits. Leavened bread dough increases in volume if it allowed to “rise” before baking. Generally, metals are better conductors of heat and electricity than are nonmetals. Unreactive argon gas, rather than air, is used to fill many light bulbs to prevent the metal filament wire inside the bulb from being destroyed through chemical reactions. Metals are typically ductile (can be drawn into wires).

Classify each statement as physical or chemical property/change. Pure metals have a higher luster (are shiny and reflect light). The surfaces of some metals become dull when exposed to air. Nitrogen gas, a relatively nonreactive material at room temperature, can form nitrogen oxides at the high temperatures of an operating automobile engine. Milk turns sour if left too long at room temperature. Diamonds are hard enough to be used as a coating for drill bits. Leavened bread dough increases in volume if it allowed to “rise” before baking. Generally, metals are better conductors of heat and electricity than are nonmetals. Unreactive argon gas, rather than air, is used to fill many light bulbs to prevent the metal filament wire inside the bulb from being destroyed through chemical reactions. Metals are typically ductile (can be drawn into wires). C C C P C P C P

Real Life Problem: Designing the Penny COST of materials is an issue when manufacturing coins and paper money. Early 1980’s copper became too expensive to be used as primary metal in pennies Zinc replaced most of the copper in all post 1982 pennies PROs - Zinc – about as hard; almost as dense, readily available and less expensive than copper CONs – more chemically reactive (zinc-plated steel pennies created in 1943 corroded and looked considerably different)

(increase coin’s durability and maintain familiar appearance) Solved the penny issue in early 1980s Copper properties best fit for outside of the coin and zinc properties best fit for inside of the coin (increase coin’s durability and maintain familiar appearance)

PHYSICAL Changes CHEMICAL changes that alter a substance’s appearance without changing its composition chemical reactions process that involves 1 or more substances changing into new substances Ex. Cutting paper, breaking crystals, melting/freezing ice, boiling water Ex. combusts, rusts, reacts with oxygen, ferments, burns, rots http://vital.cs.ohiou.edu/steamwebsite/downloads/ChangeLab.swf Online Quiz http://www.teachertube.com/viewVideo.php?video_id=214083

Density is the Mass per unit Volume What is Density? If you take the same volume of different substances, then they will weigh different amounts. Wood Water Iron 1 cm3 1 cm3 1 cm3 IRON 0.50 g 1.00 g 8.00 g Q) Which has the greatest mass and therefore the most dense? Density is the Mass per unit Volume http://www.youtube.com/watch?v=GMNpPgLT8Fk

Density Equation: mass Density = Volume M = D x V V = M / D g mL (for liquids) or cm3 (for solids) g/mL or g/cm-3 http://science360.gov/obj/video/f2511bad-b43f-4dbd-84f9-ace57941ac90/mass-volume-density NHL Hockey Rinks

DENSITY OF A REGULAR SOLID Find the Mass of the solid on a balance. Measure the three lengths and calculate the Volume. (ie V = l x w x h ) Calculate the Density. m = 240 g 2.0 cm  = m = 240 =10.0 g/cm3 V 24 3.0 cm 4.0 cm

DENSITY OF AN IRREGULAR SOLID 1. Find the Mass of the solid on a balance. 2. Fill the Measuring Cylinder with Water to a known Volume. 3. Add the Object. 4. Work out the Volume of Water that is displaced. 5. Calculate the Density. m = 360 g 80 ml 50 ml Density = m = 360 =12.0 g/cm3 V 30

DENSITY OF AN IRREGULAR SOLID OR use a Eureka (overflow) Can to find the Volume. 1. Find the mass of the solid on a balance. 2. Add water until just overflowing. 3. Place a Measuring Cylinder under the spout. 4. Add the Object. 5. Collect the Water and read off the Volume. 6. Calculate Density m = 440 g 40.0 ml Density = m = 440 =11.0 g/cm3 V 40

DENSITY OF A LIQUID Find the Mass of an empty graduated cylinder. 2. Add a certain Volume of Liquid. Find the Mass of the Measuring Cylinder and Liquid 4. Calculate the Mass of Liquid. How? Mass of Liquid = Mass of Measuring Cylinder and Liquid – Mass of empty Measuring Cylinder Calculate Density of Liquid. 45.0 g 25.0 g 25.0 g 20.0 ml 45 – 25 = 20 g Density = m = 20 =1.00 g/mL V 20

Density Practice Problems What is the density of a piece of wood that has a mass of 25.0 grams and a volume of 29.4 cm3? 2. A piece of wood that measures 3.0cm by 6.0cm by 4.0 cm has a mass of 80.0 grams. What is the density of the wood? Would the piece of wood in #2 float in water? Yes, the wood’s density is less than the density of water (1.0g/cm3) D = 25.0g 29.4cm3 D = 0.85g/cm3 Density = m V Volume = l x w x h Density = m V D = 80.0g 72.0cm3 D = 0.85g/cm3 V = 3.0cm x 6.0cm x 4.0cm V = 72.0cm3 m = 80.0g

An ice cube measuring 5.80cm by 5.80cm by 5.80cm has a density of 0.917g/cm3. What is the mass? 5. The density of aluminum is 2.7g/ml. If the mass of a piece of aluminum is 244g, what is the volume of the aluminum? V = 5.8cm x 5.8cm x 5.8cm V = 195.11cm3 D = 0.917g/cm3 Volume = l x w x h Density = m V m = D x V m = 0.917g/cm3 x 195.11cm3 m = 178.92g V = 244g 2.7g/ml V = 90.37ml D = 2.7g/ml m = 244g D = m V V = m D

How to TEST for GASSES! Oxygen (O2), Hydrogen (H2) & Carbon Dioxide (CO2)  colorless and odorless (for the most part)…. SOOO how can you tell which gas is emitted after a chemical reaction????? http://www.youtube.com/watch?v=LiAvDpl5aJA