Chemical Properties & Physical and Chemical Changes

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. 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. 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? 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


•Burning Paper

•CHEMICAL


•Digestion of food

•CHEMICAL


•Sugar dissolving in water

•PHYSICAL


•Iron turning red when heated

•PHYSICAL


•Evaporation

•PHYSICAL


•A pond freezing in winter

•PHYSICAL


•Melting ice

•PHYSICAL


•Cutting wire

•PHYSICAL


•Painting fingernails

•PHYSICAL


•Cutting fabric

•PHYSICAL


•Baking muffins

•CHEMICAL


•Shattering glass

•PHYSICAL


•Decomposition of old leaves

•CHEMICAL


•Wrinkling a shirt

•PHYSICAL


•An old nail rusting

•CHEMICAL

PHYSICALProperties

- 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. 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.

1. Pure metals have a higher luster (are shiny and reflect light).2. The surfaces of some metals become dull when exposed to air.3. Nitrogen gas, a relatively nonreactive material at room

temperature, can form nitrogen oxides at the high temperatures of an operating automobile engine.

4. Milk turns sour if left too long at room temperature.5. Diamonds are hard enough to be used as a coating for drill bits.6. Leavened bread dough increases in volume if it allowed to “rise”

before baking.7. Generally, metals are better conductors of heat and electricity than

are nonmetals.8. 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.

9. Metals are typically ductile (can be drawn into wires).

Classify each statement as physical or chemical property/change.

1. Pure metals have a higher luster (are shiny and reflect light).2. The surfaces of some metals become dull when exposed to air.3. Nitrogen gas, a relatively nonreactive material at room

temperature, can form nitrogen oxides at the high temperatures of an operating automobile engine.

4. Milk turns sour if left too long at room temperature.5. Diamonds are hard enough to be used as a coating for drill bits.6. Leavened bread dough increases in volume if it allowed to “rise”

before baking.7. Generally, metals are better conductors of heat and electricity than

are nonmetals.8. 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.

9. Metals are typically ductile (can be drawn into wires).

P

C

CC

P

C

P

CP

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)

• 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)

PHYSICALChanges

CHEMICALChanges

- 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://www.teachertube.com/viewVideo.php?video_id=214083

http://vital.cs.ohiou.edu/steamwebsite/downloads/ChangeLab.swfOnline Quiz

What is Density?

Density is the Mass per unit Volume

Wood Water Iron

1 cm3

1 cm3

1 cm3

If you take the same volume of different substances, then they will weigh different amounts.

0.50 g 1.00 g 8.00 g

Q) Which has the greatest mass and therefore the most dense?

IRON

http://www.youtube.com/watch?v=GMNpPgLT8Fk

Density = mass

Volume

g

mL (for liquids)

or cm3 (for solids)

g/mL or g/cm-3

Density Equation:

M = D x VV = M / D

http://science360.gov/obj/video/f2511bad-b43f-4dbd-84f9-ace57941ac90/mass-volume-density

NHL Hockey Rinks

DENSITY OF A REGULAR SOLID

1. Find the Mass of the solid on a balance.2. Measure the three lengths and calculate the Volume. (ie V = l x w x h )

• Calculate the Density.

4.0 cm

2.0 cm

3.0 cm

= m = 240 =10.0 g/cm3

V 24

m = 240 g

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.

50 ml

80 ml

m = 360 g

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 LIQUID1. Find the Mass of an empty graduated cylinder.2. Add a certain Volume of Liquid.3. Find the Mass of the Measuring Cylinder and Liquid4. Calculate the Mass of Liquid.

• How?

1. Mass of Liquid = Mass of Measuring Cylinder and Liquid – Mass of empty Measuring Cylinder

2. Calculate Density of Liquid.

25.0 g

20.0 ml

45.0 g

45 – 25 = 20 gDensity = m = 20 =1.00 g/mL V 20

25.0 g

Density Practice Problems1. 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?

3. 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)

Density = m V

D = 25.0g 29.4cm3

D = 0.85g/cm3

Volume = l x w x hDensity = m V V = 3.0cm x 6.0cm x 4.0cm

V = 72.0cm3

m = 80.0g

D = 80.0g 72.0cm3

D = 0.85g/cm3

4. An ice cube measuring 5.80cm by 5.80cm by 5.80cmhas 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?

Volume = l x w x hDensity = m V m = D x V

V = 5.8cm x 5.8cm x 5.8cmV = 195.11cm3

D = 0.917g/cm3

m = 0.917g/cm3 x 195.11cm3

m = 178.92g

D = 2.7g/mlm = 244g

D = m VV = m D

V = 244g 2.7g/ml

V = 90.37ml

http://www.youtube.com/watch?v=LiAvDpl5aJA

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?????

Chemical Properties & Physical and Chemical Changes

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