Transcript Testing - Dallas School District

The top of a small table is 0.500 m2.
a. Calculate how many square inches it is (1.000
inch =2.540 cm)
b. Is the table top a pure substance?
c. If the table is sawed in half, is that a physical or
chemical change?
d. If the table is burned, is that a physical or
chemical change?
e. If the table floats in water (before being
burned), what does that tell you about the
spacing of the molecules compared to water?
1. Is ice water homogeneous or heterogeneous?
2. Is freezing a chemical or physical change?
3. Is baking cookies a chemical or physical
change?
4. How do molecules differ in a liquid than a
solid?
5. A soda can has a radius of 3.25 cm and a height
of 12.00 cm.
a. Calculate the volume of the can (398 cm3)
b. The can has a mass of 557 g. Calculate the density.
(1.39 g/cm3)
c. Convert the density to kg/m3. (1390 kg/m3)
Pure Substances
1. Pure Substances – either all one element or all
one compound. Have definite unchanging
properties
2. Types
a) Elements –Au, O2
b) Compounds – pure water
Homogeneous Mixtures
1.Uniform mixture of two or more elements
and compounds (only one phase)
2.Types
a) Solutions – liquid homogeneous mixtures
Examples
Solute
Solvent
Kool-Aid
Salt Water
Homogeneous Mixtures
b) Alloys – Solid uniform mixtures. Usually
metals.
Stainless Steel – Iron and Chromium
Brass – Copper and Zinc
Bronze – Copper and tin
Heterogeneous Mixtures
1. Nonuniform mixture, composed of two or more
phases
2. Phase – One physical state with definite boundaries
3. Examples:
Ice Water – Two Phases (water & ice)
Italian dressing – More than two phases
Granite – Multiple phases
Zinc and Sulfur
Physical Properties
1. Can be observed without changing the substance
into another substance
2. Examples:
Melting Point/Freezing Point
Boiling Point
Hardness
Solubility
Malleability
Ductility
Position
Volume
Attraction
Solid
Fixed (close
together)
Definite
Strong (close
together)
Liquid
Atoms wander
(close
together)
Atoms wander
(far apart and
fast)
Definite
Strong (close
(takes shape together)
of container)
Gas
Plasma Ions and
electrons
wander
Expand to fill
container
(can be
compressed)
Expand to fill
container
Weak or no
attraction (too
far apart)
Weak or no
attraction (too
far apart)
Solids
Can “wiggle”
in place
(these are the
wiggle lines)
Liquids
They wander in
random patterns
quite close to one
another.
Gases
• Plasma - 4th state of matter
• Ionized gases
Plasma
– Electrons removed from the atoms
– Positive ions remain
• Present in:
– Stars
– Lightning
– Arc welding
• Most common state of matter in the
universe
Plasma
hydrogen and helium plasma (sun)
e
He+
e
H+
H+
H+
e
He+
e
e
He+
e
e
He+
e
H+
Can an elephant swim?
Can an elephant swim?
Physical Properties : Density
1. History – Archimedes story
2. Density = mass per unit volume
3. D = m/V
Mass  Grams
V
 mL or (cm3)
D
 g/mL
4. Intensive property – does not depend on amount
present
5. Volume formulas
Rectangular
Cylinder
Irregular shape (Archimedes)
6. Solving for variables
a. Algebra
3 = x/8
2 = 6/x
b. Density
Solve for m
Solve for V
1. A ring has a mass of 8.99 g and a volume of
0.796 mL. Is the ring gold (19.3 g/mL)? (Ans:
11.3 g/mL)
2. A substance masses 47.5 g. It is put into a grad
cylinder containing 12.5 mL of water. After
immersing the substance, the total volume is
31.8 mL. What is the density? (Ans: 2.46
g/mL)
3. Salt has a density of 2.16 g/mL. What is the volume of
485 g of salt? (Ans: 225 mL)
4. What is the mass of 1.520 L of kerosene (r = 0.8200
g/mL)? (Ans: 1246 g)
5. What volume would 0.450 kg of lead occupy (r = 11.3
g/cm3) (Ans: 39.8 cm3)
6. A cylinder has a radius of 2.00 cm and a height of 10.0
cm. If the cylinder is filled with 0.289 grams of a gas,
density? (Ans: 0.00230 g/cm3)
A piece of wood that measures 3.0 cm by 6.0 cm
by 4.0 cm has a mass of 80.0 grams.
a. Calculate the density of the wood.
b. Would the piece of wood float in water?
Calculate the mass of a cylinder of lead that is
2.50 cm in diameter, and 5.50 cm long. The
density of lead is 11.4 g/mL.
A rectangular sample of aluminum has the
measurements 1.34 cm by 2.58 cm by 10.00
cm.
a. Calculate the volume of the sample. (34.6 cm3)
b. Calculate the mass of the sample. The density
of aluminum is 2.70 g/cm3. (93.3 g)
c. Would the block of aluminum float in mercury
(r = 13.6 g/mL)?
d. An irregular sample of aluminum is found to
have a mass of 50.00 grams. The sample is
placed in 10.00 mL of water. Calculate the final
volume reading of the graduated cylinder. (28.5
mL)
Chemical Properties
1. Chemical Change – one substance changed into
another substance
2. Chemical Properties – tendency of a substance
to react with other substances
3. Examples
Flammability
Will it rust (oxidize)?
Acid or base?
4. Atoms rearrange and bonds are made and
broken:
2H2 + O2 
2H2 O
Recognizing a chemical change:
1. Properties change (rust is different than iron)
2. Gets hotter or colder
•
•
Exothermic – Gives off heat (burning gas, exercise)
Endothermic – Absorbs heat (cooking)
3. Color change
4. Gas given off
5. Light produced (glow stick)
Law of Conservation of Mass
A. Antoine Lavosier (1789)
B. Law of cons. of mass – mass is neither created
nor destroyed in a chemical reaction
C. Two Examples
1. 2H2 + O2  2H2O
10g + 80g  90g
2. Burning wood ?
Wood + O2  Gas + Ash.
Law of Conservation of Energy
Energy can never be created or destroyed in a
chemical reaction. It can only change form.
1. Battery: turns chemical to electrical to
mechanical energy.
2. ALWAYS lose some energy in transformations
(usually as waste heat)
Einstein:1905
Law of cons. of mass/energy – mass and energy
cannot be created or destroyed. They only
change form
E = mc2
E= Energy
m = mass
c = speed of light
2. A small amount of matter can be destroyed to
release a large amount of energy (nuclear
processes) (20 g U  18 g U)
Energy – The capacity to do work
– 1 Joule = 1 Newton-meter
– 1 calorie = amount of heat to raise one gram of
water by 1o C
1 calorie = 4.18 Joule
(1 nutritional Calorie = 1000 calories, 1 kilocalorie)
Two types
• Potential Energy - Stored
Chemical Energy – energy stored in chemical bonds
» Plants absorb energy from the sun
» That energy is released through digestion/burning
• Kinetic Energy – energy in motion
Energy of moving atoms and molecules
Specific Heat
Specific Heat – Amount of heat needed to raise the
temperature of one gram of a substance by one degree
Celsius or Kelvin
•
•
•
Unit – cal/goC or J/goC
Symbol = Cp
Higher the specific heat, the more energy needed to raise the
temperature
Predict the specific heat of the following (high or
low):
Car hood
Pot of water
Beach sand
Plants & Trees
Substance
Water
Specific Heat
(cal/goC)
1.000
Specific Heat
(J/goC)
4.184
Ice
0.492
2.06
Aluminum
0.214
0.895
Gold
0.031
0.129
Copper
0.092
0.385
Zinc
0.093
0.388
Iron
0.106
0.444
q = mCpDT
q = heat in Joules
m = mass (grams)
Cp = specific heat (J/goC)
DT = Tfinal – Tinitial
How much heat must be supplied to a 500.0
gram iron pan (Cp = 0.444 J/g oC) to raise its
temperature from 20.0oC to 100.0oC?
q = mCpDT
q = (500.0g)(0.444J/g oC)(100.0oC -20.0oC)
q = (500.0g)(0.444J/g oC)(80.0oC)
q = 17,800J or 17.8 kJ
Suppose we use a similar pan, except it is now made of
Aluminum (Cp = 0.895 J/goC)?
q = mCpDT
q = (500.0g)(0.895 J/goC)(100oC -20oC)
q = (500.0g)(0.895 J/goC)(80oC)
q = 35,800 J or 35.8 kJ
What temperature change would 50.0 g of rock
undergo if they absorbed 452 Joules of heat?
(Assume the specific heat is 0.836 J/goC).)
ANS: 10.8 oC (which is also 10.8 K)
A sample of copper (Cp = 0.092 cal/goC) undergoes
a temperature change from 24.0oC to 76.0 oC
upon the addition of 1300.0 Joules of heat.
a. Convert the heat to calories (311 cal)
b. Calculate the mass of the copper (65 g)
A 500.0 g sample of zinc absorbed 4850 J of
heat. The temperature increased from
20.00 oC to 45.00 oC.
a. Calculate the specific heat of the sample in
J/goC. (0.388 J/goC)
b. Calculate how many calories of heat the
sample absorbed. (1160 cal)
c. A separate sample of zinc absorbs the same
amount of heat. However, the temperature
only rises from 20.00oC to 28.00oC. Calculate
the mass of the sample in kilograms. (1.56
kg)
Heating Curves
1. Changes of state do not have a temperature
change.
1. Melting/Freezing
2. Boiling/Condensing
2. A glass of soda with ice will stay at 0oC until all
of the ice melts.
3. Graph “flattens out” during changes of state
Steam heats
up
Temperature
(oC)
Boiling
Melting
Water
warms up
Ice warms up
Heat (Joules)
1.
2.
3.
4.
5.
6.
Calculate the square root of 57.2 (7.56)
Calculate the cube root of 57.2 (3.85)
Calculate the cube root of 144 (5.24)
Calculate the cube root of 1,728 (12)
Calculate the 4th root of 625 (5)
Calculate the 4th root of 65,536 (16)
1. What is the volume of 0.0354 kg of gold? (1.83 cm3)
2. What mass of mercury would occupy 25.0 mL (340g)
3. Which would have a greater mass, 50 mL of water
(1g/mL) or 50 mL of vegetable oil (0.72 g/mL)
4. A piece of zinc (7.14 g/cm3) has a mass of 257 g. If the
zinc is rectangular and has a length of 1.00 cm and a
width of 4.00 cm, what is the height? (9.00 cm)
5. A cylinder of copper (8.92 g/cm3) is found to have a
mass of 1681 grams. The cylinder is 15.0 cm tall
a. Calculate the radius. (2.00 cm)
b. Would the sample float in water?
c. Would the sample float in mercury?
d. Suggest a method for measuring the volume of the
cylinder in the lab.
A 250.0 g sample of water is heated from 21.20 oC to
98.30 oC to make tea.
a. Calculate the heat required in kJ. (80.6 kJ)
b. Calculate how many calories of heat the sample
absorbed. (19.3 kcal)
c. When the same amount of heat is added to 600.0
grams of an unknown substance, the temperature
rises by 59.7 oC. Calculate the specific heat of the
unknown substance. (2.25 J/goC)
d. The unknown substance is rectangular and has
dimensions 10.0 cm by 15.0 cm by 5.00 cm. Would
the substance float in water? (r = 0.800 g/cm3)
5 a) Chemical
b) Physical
c) Physical
d) Chemical
e) Physical
7 a) Chemical
b) Chemical
c) Physical
d) Physical
8. Chemical (change in
substance)
13. 7.91 g/mL
15. 1.74 g/ml, 575 mL
16. 21.0 mL
20. 29.0 kg (29,000 g)
25. 1.11 g/mL
26. 2.51 mL
29. Lead = 88.5 cm3, Gold
= 51.8 cm3
65. 0.896 J/goC, Al
67. 2.05 J/goC
71. 1.4 oC
73. 46.7 g
74. 0.0317 cal/goC or 0.133
J/goC
83. 28.3 mL
90. 25.5 kcal
92. 0.242 cal/goC or 1.02
J/goC
63. 0.853 J/goC
64. 0.031 cal/goC
65. 0.896 J/goC, Al
66. 58 oC
67. 2.05 J/goC
68. 506 J
71. 1.4 oC
72. 9.38oC(Fe) 32oC(Au)
0.997o(H2O)
73. 46.7 g
92. 0.242 cal/goC or 1.02
J/goC
74. 0.0317 cal/goC or 0.133
J/goC
83. 28.3 mL
90. 25.5 kcal
19.1.00 gal = 3.785 L
3.785 L X 1000 mL = 3785 mL
1L
D = M/V
M = DV = (0.67 g/mL) X 3785 mL = 2536 g
2536 g X 1 lb = 5.591 lb
453.6g
20.1.50 L = 1500 mL
M = DV = (19.3 g/mL)(1500 mL) = 29,000 g
29,000 g X (1 kg/1000 g) = 29.0 kg
1. 2.70 g/mL
2. 2.33 mL
3. 135 g
4. 4.20 g/mL
5. 3.92 g/mL
6. 80.0 g
7. 2.08 g/mL
8. 26.5 g
9. 7.20 g/mL
10. 2.24 g/mL
Chapter 3 Problem Sheet – Density
a) 1.01 g/mL
k) 1.96 g/L
b) 158 g
l) 11.3 g/mL
c) 7.92 g/mL
m) 0.0018 g/mL
d) 2.70 g/mL
n) 0.0022 cm
e) 331 g
f) 2.16 g/mL
g) 13.6 g/mL
h) 225 g
i) 1.25 g/L
j) 1.59 g/mL
Measuring
Measuring
Measuring
“I would measure with a ruler with more marks to get
more significant figures. ”
“More supplies would make the experiment go faster.”
“The metal pieces should be allowed to carefully slide
down the side of the cylinder. This would prevent
splashing of the water. The splashing seen in this
experiment probably resulted in a smaller volume for the
metal pieces.
“I would do more trials to get more numbers. This should
give a more accurate average.”
Answers to Review Sheet:
1. (B)
6. (A)
2. (E)
7. (D)
3. (C)
8. (B)
4. (E)
9. (D)
5. (A) 10. (B)