2.1.3 notesName: ______

Chapter 2.2 Physical properties (p. 45)

Physical property-any characteristic of a material that you can observe without changing the composition of the substances that make up the material (i.e. color, shape, size, density, melting point, and boiling point)

  • The ratio of atoms making up the substances is not changed; no new compound or element has been formed
  • Physical change-a change in size, shape, or state of matter
  • For example, cutting up a piece of paper or sculpting a piece of clay
  • Physical change does not change the identity of the substances in the matter

Using physical properties in identifying substances:

  1. Melting point the temperature at which a substance changes from solid to liquid (i.e. when an ice cube melts)
  2. It occurs as vibrating particles within the solid gain enough energy to break into flowing motion to become particles within a liquid
  3. The freezing point is an equal temperature to the melting point (i.e. 0oC for water)
  4. A dissolved solid within a liquid usually causes the freezing/melting point to decrease (i.e. salt sprinkled on icy roads causes them to melt or remain liquid at a lower temperature than usual)
  5. Boiling point the temperature at which a liquid substance becomes a gas
  6. It occurs as flowing particles within a liquid gain enough energy to begin bouncing freely to become bubbles of gas
  7. The point of condensation is an equal temperature (100oC for water)
  8. Dissolving a solid in a liquid will usually cause its boiling point to increase
  9. For example: coolant contains dissolved solutes that keep radiator fluid from boiling at temperatures near 100oC
  10. Air pressure also affects boiling point, which is decreased at low pressures
  11. So at high altitudes, where air pressure is lower than at sea level, boiling occurs at a lower temperature

3. Density mass per unit volume

Review = mass equals amount of matter a substance contains

  • measured in kg, g, etc. on a balance or scale

Volume is the amount of space a 3-D object takes up (how tightly packed)

  • measured in mL or cm3 or m3
  • either using water displacement (irregular object) or l x w x h (regular shaped object)

Density  units are usually g/cm3 or g/mL

  • Water’s density = 1 g/cm3

Objects density / Result
Greater than 1 g/cm3 / Sinks in water
Less than 1 g/cm3 / Floats in water
  • Can use water to determine mass because 1 cm3 or 1 mL of water = 1 gram of mass

Chapter 2.3 Chemical properties (p. 54)

Chemical property- any ability to produce a change in the composition of matter

Examples:

  1. flammability- tendency of a substance to burn
  2. reactivity – how readily a substance combines chemically with other substances; O2 is highly reactive (reacts with iron to form rust); nitrogen has an extremely low reactivity (doesn’t easily combine with other elements)
  • Can be described as non-reactive (Noble gases), slightly reactive, reactive and highly reactive (alkali metals and halogens)
  • Vary according to groups on the periodic table

Chemical change - substances react and form one or more different substances (i.e. iron + air = rust; hydrogen gas + oxygen gas = water)

  • Properties or the original substances changes as new substances are formed with different properties

How do we know if a chemical change has occurred???

  1. Production of a gas:
  • For example: when reactions produce bubbles
  • Including the “eating” of metals by an acid
  • Can produce H2 (gas) or CO2 (gas)
  • 2HCl + 2Zn  2ZnCl + H2
  1. Formation of precipitate:
  • Precipitate = solid that suddenly settles out of a liquid or gaseous mixture
  • Precipitates are insoluble
  • For example: KI(l) + Pb(NO3)2(l)  2 PbI2 (s) + KNO3(l)
  • The PbI2 will become insoluble (a solid precipitate) and fall to the bottom of the test tube
  1. Release or absorption of energy (heat or light):
  • Endothermic chemical reactions – heat is needed to break the chemical bonds in order for the reaction to occur
  • Makes the container feel cool to the touch because it is pulling heat from the surroundings
  • Example: Barium hydroxide and ammonium chloride in water (Glencoe Book; p.649)
  • Exothermic chemical reactions – heat is given off during a chemical reaction
  • Less energy is required to break the original bonds than is released when new bonds form
  • Example: The burning of wood or fossil fuels (coal, petroleum, natural gas)
  • Example: the explosion of dynamite

Summary

D = m/vdensity is measured in g/mL or g/cm3mass is measured in g volume is measure in mL or cm3

Volume = length x width x height

To calculate volume for things where you can’t measure l x w x h, use water displacement

Samples:

1. The density of aluminum is 2.7 g/cm3. A piece of aluminum foil has a volume of 54 cm3. What is the mass of this piece of aluminum foil?

A. 145.8gb. 20gc. 14.58gd. 0.05g

2. What is the density of a piece of silver that has a mass of 210g and a volume of 20.0cm3?

a. 4200 g/cm3b. 230g/cm3 c. 190g/cm3d. 10.5g/cm3

3. Which instrument would be best to use if finding the volume of an irregularly shaped object is required when calculating density?

A. a metric tape measureb. a meterstick

c. a graduated cylinderd. a Erlenmeyer flask

4. Shelby pours a sample of pure bromine into a graduated cylinder, as shown in the diagram to the right. If the mass of the sample itself is 198.4g, what is the density of the bromine?

A. 35g/mLb. 5.67g/mLc. 0.18g/mLd. 19.2g/mL

5. The densities of three immiscible liquids are as follows: liquid X: 1g/ml liquid Y: 0.78g/mL liquid Z: 1.45g/mL The three liquids are poured slowly into a tall graduated cylinder and soon separated into three distinct layers. Which one of the following arrangements, starting from the top layer on down, indicates the correct order of the substances?

a. XYZb. ZYXc. XZYd. YXZ

6. A graduated cylinder contains 25mL of water. The mass of the cylinder and water was 68.0g. A small stone is lowered into the cylinder. The water level rises to the 30.0mL mark, and the mass of the cylinder, water and stone is now 78.0g. Select the density of the small stone.

a. 2.00g/mLb. 10.0g/mLc. 0.50g/mLd. 5.00g/mL

7. Jamonddrops an object w/ a mass of 7.6g and a volume of 7cm3 in a container of gasoline. Gasoline has a density of 0.7g/cm3. Which of the following statements describes what will happen to the object?

a. The object will float b/c it is less dense than gasoline

b. the object will float b/c it is more dense than gasoline

c. the object will sink b/c it is less dense than gasoline

d. the object will sink b/c it is more dense than gasoline

8. Given this information: W has a density of 19.25 g/cm3, Fe has a density of 7.86 g/cm3, Mg has a density of 1.74g/cm3 and Al has a density of 2.7 g/cm3. Shi has a 4g sample of an unknown metal. His job in lab is to figure out which metal it is. Using water displacement, he determines that his sample has a volume of about 0.5cm3. Which metal is Shi’s sample?

a. tungstenb. ironc. magnesiumd. aluminum

9. Which is denser? Water or mercury?

Summary

Phase changes are physical! When something melts, boils, freezes, condenses, sublimates, etc. IT IS PHYSICAL!!

A physical property is a characteristic that can be observed w/o changing the composition of the substance.

Boiling point, melting point, freezing point, density, solubility, viscosity, conductivity, elasticity, hardness, toughness, ductility, size, shape, color, etc. are all physical properties.

A chemical change is any change that results in the formation of new substances.

3 evidences of chemical change:

  1. production of a gas (bubble, fizzes, smokes)
  2. formation of a precipitate (a precipitate is a solid that forms when two liquids are mixed)
  3. release or absorption of energy (endo or exo)

Which is the precipitate?

AgNO3(aq) + NaCl(aq) ---> AgCl(s) + NaNO3(aq)

Endothermic requires heat or energy for the reaction to take place, so the container will become cold. Energy is a reactant.

Exothermic releases heat or energy, so the container will become hot. Energy is a product.

Endo = cold BOTH 4 LETTERS!

Exo = hot BOTH 3 LETTERS!

Samples:

1. When copper reacts w/ oxygen in the air, a color change takes place, and the copper becomes green. This green color is called patina. What type of change occurs to produce patina?

a. physicalb. chemical c. conduction d. combustion

2. Which change describes a chemical change?

a. formation of hydrogen gas when a metal is placed in a strong acid

b. evaporation of water from a puddle on a hot, summer afternoon

c. finding the density of a piece of silver by measuring its mass and volume

d. hammering of aluminum metal into a thin sheet to be used for aluminum foil

3. Which change is a chemical change?

a. electrolysis of water into hydrogen and oxygen gases

b. evaporation of water from a puddle on a hot summer afternoon

c. hammering of gold metal into thin sheets to be used for gold leaf

d. melting silver before pouring it into a mold

4. Which of the following is an example of a physical change?

a. formation of silver sulfide when silver reacts in the air

b. burning of methane gas, which produces water and carbon dioxide

c. condensation of water vapor on the outside of a cold can of soda

d. vinegar and baking soda combining and forming a salt and water

5. Which one of the following choices is NOT a physical change?

a. sawing a wooden board in halfb. breaking up lumps of sugar

c. burning a piece of paper d. painting a house

6. Inflating a rubber balloon and then deflating it to its original size shows that rubber possesses the physical property of

a. elasticityb. plasticityc. ductilityd. malleability

7. Which activity involves a physical change rather than a chemical change?

a. burning wood in a fireplace b. ice forming on a pond

c. baking pumpkin bread d. leaves producing glucose in the spring

8. Which illustrates a physical change?

A. a candle burning b. water freezing

c. fireworks explodingd. leaves decomposing

9. Which is an example of a physical change?

a. solid ice cubes change into liquid water when they melt at 0C.

b. an egg in the hot pan on the gas burner changes from liquid to solid after it cooks.

c. a piece of paper burns when it is thrown into a fire.

d. a green plant transforms carbon dioxide and water into glucose during photosynthesis.

10. Which process involves only a physical change?

A. sublimation b. combustion c. electrolysis d. nuclear fusion

11. Which process represents a chemical change?

A. melting of iceb. corrosion of iron

c. evaporation of alcohold. crystallization of sugar

12. When solutions of silver nitrate and sodium chloride are mixed, silver chloride, a solid white substance, forms. What is the name given to a solid substance that forms when two solutions are mixed?

a. acidb. liquidc. precipitated. gas

13. Which of the following is an example of a physical change?

a. formation of silver sulfide when silver reacts with sulfur in the air

b. burning of methane gas produces water and carbon dioxide

c. condensation of water vapor on the outside of a cold can of soda

d. vinegar and baking soda combine and form a salt and water

14. The general formula for photosynthesis is 6CO2 + 6H2O + ENERGY ---> C6H12O6 + 6O2. Which best describes this reaction?

a. it’s exothermic b. it releases heat energy

c. it’s endothermicd. the equation cannot be balanced.

15. A clear liquid & a white powder were combined & then quickly sealed in a plastic bag. The bag expanded, was warm to the touch, bubbles formed, & the powder & liquid both changed color. Which statement would be the best conclusion?

a. There is no way to know whether this was a chemical or physical change.

b. The bag expanded b/c the liquid and powder formed a solution.

c. Temperature and color change in this experiment indicate only a physical change could have occurred.

d. Temperature and color change, as well as the formation of a gas, indicated a chemical reaction has most likely occurred.

16. For which type of chemical reactions would having a fire extinguisher close by be most necessary?

a. oxidation reactionsb. neutralization reactions

c. exothermic reactionsd. endothermic reactions

17. An unknown gas is colorless, odorless, and tasteless. The gas turns moist iron filing reddish-brown. It condenses to a liquid at –183 ºC. Which fact is a chemical property of the gas?

a. it condenses at –183 ºCb. it turns iron reddish-brown

c. it is colorlessd. it is odorless

18. Liquid A was red and liquid B was clear. When 10 drops of liquid B were added to liquid A, the red color turned clear and the new solution became warm. What is the most likely explanation of what took place?

a. A chemical reaction occurred b/c the new solution had a greater volume

b. a phys. change occurred b/c in the increase in temp.

c. a chemical change probably occurred b/c there was change in color and also an increase in temperature

d. a phys. change occurred b/c it is now a solution.

19. Which includes a chemical change?

a. Chris cuts down a large oak tree.

b. Chasity strips the tree of its limbs and leaves and chips them into smaller pieces

c. Francisco cuts the trunk into fire logs.

d. Ashley burns all of the small twigs and leaves.

20. Select the observation that doesn’t support the conclusion that a chemical reaction took place.

a. temperature rose b. an odor developed

c. a precipitate was formed d. liquid water changed to water vapor

21. Which of the following supports the conclusion that a chemical reaction has occurred?

a. adding salt to a salt water solution results in salt settling to the bottom of the beaker

b. heating a salt solution on a hot plate raises its temperature

c. shining a flashlight through a beaker of salt solution causes a refraction of the light

d. adding an acid to a salt solution raises its temperature.

22. Kacy has two test tubes full of water. She boils the water in Test Tube A. She adds green food coloring to the water in Test Tube B. In which test tube did a chemical change take place?

a. Ab. B c. bothd. neither test tube

23. Caleb has two magnesium samples. One is a small, solid block. The other is a vial of powdered magnesium. He adds the small block of Mg to a water sample. Small bubbles slowly begin to form at the surface of the block. What will happen to the powdered Mg sample if Caleb adds it to a separate beaker of water?

a. The Mg sample will disappear.

b. the Mg sample will change color

c. the Mg sample will bubble much more slowly than the solid sample did

d. the Mg sample will bubble much more quickly than the solid sample did.