Chapter 4 Matter and Energy Vanessa N. Prasad-Permaul CHM 1025 Valencia Community College 1.

Chapter 4

Matter andEnergy

Vanessa N. Prasad-Permaul

CHM 1025

Valencia Community College

1

Matter

Matter is any substance that has mass and occupies volume.

Matter exists in one of three physical states:

1. Solid

2. Liquid

3. Gas

2

Gaseous State

In a gas, the particles of matter are far apart and uniformly distributed throughout the container.

Gases have an indefinite shape and assume the shape of their container.

Gases can be compressed and have an indefinite volume.

Gases have the most energy of the three states of matter.

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Liquid State

In a liquid, the particles of matter are loosely packed and are free to move past one another.

Liquids have an indefinite shape and assume the shape of their container.

Liquids cannot be compressed and have a definite volume.

Liquids have less energy than gases, but more energy than solids.

4

Solid State

In a solid, the particles of matter are tightly packed together.

Solids have a definite, fixed shape.

Solids cannot be compressed and have a definite volume.

Solids have the least energy of the three states of matter.

5

Physical States of Matter

6

Changes in Physical States Most substances can exist as either a

solid, a liquid, or a gas.

Water exists as a solid below 0 °C; as a liquid between 0 °C and 100 °C; and as a gas above 100 °C.

A substance can change physical states as the temperature changes.

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Solid ↔ Liquid Phase Changes When a solid changes to a liquid, the

phase change is called melting.

A substance melts as the temperature increases.

When a liquid changes to a solid, the phase change is called freezing.

A substance freezes as the temperature decreases.

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Liquid ↔ Gas Phase Changes When a liquid changes to a gas, the

phase change is called vaporization.

A substance vaporizes as the temperature increases.

When a gas changes to a liquid, the phase change is called condensation.

A substance condenses as the temperature decreases.

9

Solid ↔ Gas Phase Changes When a solid changes directly to a

gas, the phase change is called sublimation.

A substance sublimes as the temperature increases.

When a gas changes directly to a solid, the phase change is

called deposition. A substance undergoes

deposition as the temperature decreases.

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Summary of State Changes

11

EXAMPLE 4.1 Change of Physical State

Refer to Figure 4.1 for the changes of physical state.(a) The change from solid to liquid is called melting.(b) The change from liquid to gas is called vaporizing.(c) The change from solid to gas is called sublimation.

Solution

State the term that applies to each of the following changes of physical state:(a)Snow changes from a solid to a liquid.(b)Gasoline changes from a liquid to a gas.(c) Dry ice changes from a solid to a gas.

Figure 4.1 Changes in Physical State As temperature increases, a solid melts to a liquid and then vaporizes into a gas. As temperature decreases, a gas condenses to a liquid and then freezes to a solid.

EXERCISE 4.1 Change of Physical State

Practice Exercise

State the term that applies to each of the following changes of physical state:(a)A refrigerant changes from a gas to a liquid.(b)Water changes from a liquid to a solid.(c) Iodine vapor changes from a gas to a solid.

Figure 4.1 Changes in Physical State As temperature increases, a solid melts to a liquid and then vaporizes into a gas. As temperature decreases, a gas condenses to a liquid and then freezes to a solid.

EXERCISE 4.1 Change of Physical State

Identify the physical state (solid, liquid, gas) that corresponds to each of the following pictorial representations:

Concept Exercise

Classifications of Matter Matter can be divided into two classes:

1. Mixtures

2. Pure substances

Mixtures are composed of more than one substance and can be physically separated into its component substances.

Pure substances are composed of only one substance and cannot be physically separated.

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Mixtures

There are two types of mixtures:1. Homogeneous mixtures

2. Heterogeneous mixtures

Homogeneous mixtures have uniform properties throughout. Salt water is a homogeneous mixture.

Heterogeneous mixtures do not have uniform properties throughout. Sand and water is a heterogeneous

mixture.16

Pure Substances

There are two types of pure substances:

1. Compounds

2. Elements

Compounds can be chemically separated into individual elements.

Water is a compound that can be separated into hydrogen and oxygen.

An element cannot be broken down further by chemical reactions.

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Matter Summary

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EXAMPLE 4.2 Element, Compound, or Mixture

Refer to Figure 4.2 to classify each sample.(a) Copper wire is a metallic element.(b) Copper oxide is a compound of the elements

copper and oxygen.(c) Malachite ore is a heterogeneous mixture of

copper and other substances.(d) Bronze alloy is a homogeneous mixture of copper and tin.

Solution

Consider the following properties of the element copper:

Figure 4.2 Classification of Matter Matter may be either a mixture or a pure substance. The properties of a heterogeneous mixture vary within the sample (oil and water). The properties of a homogeneous mixture are constant (salt solution). A pure substance may be either a compound (water) or an element (gold). Left to right: oil and water; NaCl solution; H2O; and gold nugget.

(a) Copper metal cannot be broken down by a chemical change.(b) Copper reacts with oxygen in air to give copper

oxide.(c) Copper, in the form of malachite ore, is found

worldwide.(d) Copper and tin compose bronze alloy.

Classify each of the following copper samples as an element, a compound, a homogeneous mixture, or a heterogeneous mixture:(a) copper wire (b) copper oxide(c) malachite ore (d) bronze alloy

EXERCISE 4.2 Element, Compound, or Mixture

Consider the following properties of the element mercury:(a)Mercury liquid cannot be broken down by a chemical change.(b)Mercury oxide can be heated to give mercury and oxygen gas.(c) Mercury, in the form of cinnabar ore, is found in Spain and Italy.(d)Mercury and silver compose the alloy used for dental fillings.

Classify each of the following mercury samples as an element, a compound, a homogeneous mixture, or a heterogeneous mixture:(a)mercury liquid (b) mercury oxide(c) cinnabar ore (d) dental alloy

Practice Exercise

EXERCISE 4.2 Element, Compound, or Mixture

Classify each of the following as an element, a compound, or a mixture as shown in the illustration:

Concept Exercise

Occurrence of the Elements

There are over 100 elements that occur in nature; 81 of those elements are stable.

Only 10 elements account for 95% of the mass of Earth’s crust:

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Elements in the Human Body Oxygen is the most common

element in Earth’s crust and in the human body.

While silicon is the second most abundant element in Earth’s crust, carbon is the second most abundant in the body.

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Names of the Elements

Each element has a unique name.

Names have several origins: Hydrogen is derived from Greek.

Carbon is derived from Latin.

Scandium is named for Scandinavia.

Nobelium is named for Alfred Nobel.

Yttrium is named for the town of Ytterby, Sweden.

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Element Symbols

Each element is abbreviated using a chemical symbol.

The symbols are one or two letters long. Most of the time, the symbol is derived

from the name of the element. C is the symbol for carbon. Cd is the symbol for cadmium.

When a symbol has two letters, the first is capitalized and the second is lowercase.

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Other Element Symbols For some elements, the chemical symbol

is derived from the original Latin name.

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Gold – Au Sodium – Na

Silver – Ag Antimony – Sb

Copper – Cu Tin – Sn

Mercury – Hg Iron – Fe

Potassium – K Tungsten – W

Types of Elements

Elements can be divided into three classes:

1. Metals

2. Nonmetals

3. Semimetals or metalloids

Semimetals have properties midway between those of metals and nonmetals.

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Metal Properties

Metals are typically solids with high melting points and high densities and have a bright, metallic luster.

Metals are good conductors of heat and electricity.

Metals can be hammered into thin sheets and are said to be malleable.

Metals can be drawn into fine wires and are said to be ductile.

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Nonmetal Properties

Nonmetals typically have low melting points and low densities and have a dull appearance.

Nonmetals are poor conductors of heat and electricity.

Nonmetals are not malleable or ductile and crush into a powder when hammered.

Eleven nonmetals occur naturally in the gaseous state.

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Summary of Properties

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Periodic Table of the Elements Each element is assigned a number

to identify it. It is called the atomic number.

Hydrogen’s atomic number is 1; helium is 2; up to uranium, which is 92.

The elements are arranged by atomic number on the periodic table.

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The Periodic Table

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Metals, Nonmetals, & Semimetals Metals are on the left side of the periodic

table, nonmetals are on the right side, and the semimetals are in between.

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Physical States of the ElementsShown are the physical states of the elements at 25 °C

on the periodic table.

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Law of Definite Composition The law of definite composition

states that “Compounds always contain the same elements in a constant proportion by mass.”

Water is always 11.19% hydrogen and 88.81% oxygen by mass, no matter what its source.

Ethanol is always 13.13% hydrogen, 52.14% carbon, and 34.73% oxygen by mass.

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Chemical Formulas A particle composed of two or more

nonmetal atoms is a molecule.

A chemical formula is an expression of the number of and types of atoms in a molecule.

The chemical formula of sulfuric acid is H2SO4.

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Writing Chemical Formulas The number of each type of atom in a

molecule is indicated with a subscript in a chemical formula.

If there is only one atom of a certain type, no “1” is used.

A molecule of the vitamin niacin has six carbon atoms, six hydrogen atoms, two nitrogen atoms, and one oxygen atom. What is the chemical formula?

C6H6N2O37

Interpreting Chemical Formulas Some chemical formulas use parentheses

to clarify atomic composition.

Ethylene glycol, a component of some antifreezes, has a chemical formula of C2H4(OH)2. It contains two carbon atoms, four hydrogen atoms, and two OH units, giving a total of six hydrogen atoms and two oxygen atoms. How many total atoms are in ethylene glycol?

Ethylene glycol has a total of ten atoms.

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Physical and Chemical Properties A physical property is a characteristic

of a pure substance that we can observe without changing its composition.

Physical properties include appearance, melting and boiling points, density, conductivity, and physical state.

A chemical property describes the chemical reactions of a pure substance.

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Chemical Properties

Sodium metal (Na) reacts withchlorine gas (Cl2)

to producesodium chloride

(NaCl).

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Physical and Chemical Change A physical change is a change

where the chemical composition of the substance is not changed.

These include changes in physical state or shape of a pure substance.

A chemical change is a chemical reaction.

The composition of the substances changes during a chemical change.

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Evidence for Chemical Changes Gas release (bubbles)

Light or release of heat energy

Formation of a precipitate

A permanent color change

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Conservation of Mass

Antoine Lavoisier found that the mass of substances before a chemical change was always equal to the mass of substances after a chemical change.

This is the law of conservation of mass.

Matter is neither created nor destroyed in physical or chemical processes.

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Conservation of Mass Example If 1.0 gram of hydrogen combines with

8.0 grams of oxygen, 9.0 grams of water is produced.

Consequently, 3.0 grams of hydrogen combine with 24.0 grams of oxygen to produce 27.0 grams of water.

If 50.0 grams of water decompose to produce 45.0 grams of oxygen, how many grams of hydrogen are produced?

50.0 g water – 45.0 g oxygen = 5.0 g hydrogen

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Potential and Kinetic Energy Potential energy, PE, is stored energy;

it results from position or composition.

Kinetic energy, KE, is the energy matter has as a result of motion.

Energy can be converted between the two types.

A boulder at the top of the hill has potential energy; if you push it down the hill, the potential energy is converted to kinetic energy.

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Energy

46

KE, Temperature, and Physical State

All substances have kinetic energy regardless of their physical state.

Solids have the lowest kinetic energy, and gases have the greatest kinetic energy.

As you increase the temperature of a substance, its kinetic energy increases.

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Law of Conservation of Energy Just like matter, energy cannot be created or

destroyed, but it can be converted from one form to another.

This is the law of conservation of energy.

There are six forms of energy:

1. Heat

2. Light

3. Electrical

4. Mechanical

5. Chemical

6. Nuclear48

Energy and Chemical Changes In a chemical change, energy is

transformed from one form to another. For example:

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Law of Conservation of Mass and Energy

Mass and energy are related by Einstein’s theory of relativity, E = mc2.

Mass and energy can be interchanged.

The law of conservation of mass and energy states that

the total mass and energy of the universe is constant.

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Chemistry Connection: Al Recycling Although aluminum is

very abundant in Earth’s crust, it is difficult to purify it from its ore.

The energy from 8 tons of coal is required to produce 1 ton of aluminum metal from its ore.

However, it only takes the energy from 0.4 tons of coal to produce 1 ton of aluminum from recycled scrap. 51

Chapter Summary

Matter exists in three physical states:

1. Solid

2. Liquid

3. Gas

Substances can be converted between the three states.

Substances can be mixtures or pure substances.

52

Chapter Summary, Continued Pure substances can be either

compound or elements.

The elements are arranged in the periodic table.

Each element has a name and a one- or two-letter symbol.

Elements are classified as either metals, nonmetals, or semimetals.

53

Chapter Summary, Continued A physical change is a change in

physical state or shape.

A chemical change is a change in the chemical composition of a substance.

Both mass and energy are conserved in chemical and physical changes.

54

EXAMPLE EXERCISE 4.3 Properties of Metals

Refer to Table 4.4 to classify each of the following properties:(a) Metals are good conductors of heat.(b) Metals are malleable.(c) Metals usually have high melting points.(d) Metals do not react with other metals; they mix to form alloys.

Solution

Which of the following properties is not characteristic of a metal?(a) good conductor of heat (b) malleable(c) high melting point (d) reacts with other metals

EXAMPLE EXERCISE 4.3 Properties of Metals

Which of the following properties is not characteristic of a nonmetal?(a) insulator of electricity(b) ductile(c) low density (d) reacts with nonmetals

Practice Exercise

Continued

Which of the following is a solid metal under normal conditions: calcium, phosphorus, mercury, or silicon? (Refer to Figure 4.7.)

Concept Exercise

Answer: See Appendix G.

Answer: (b) Nonmetals crush to a powder and are not malleable or ductile.

Figure 4.7 Pictorial Periodic Table of the Elements The natural abundance is the percent by mass of an element in Earth’s crust, oceans, and atmosphere. The natural abundance of an element listed as rare is less than 1 mg per metric ton (1000 kg). An element listed as synthetic is made artificially and does not occur naturally. An element listed as unstable often disintegrates in a fraction of a second.

EXAMPLE EXERCISE 4.4 Physical States of the Elements

Referring to Figures 4.5 and 4.6, we observe the following:(a) Barium (Ba) is on the left side of the periodic table; it is a solid metal under normal conditions.(b) Boron (B) is in the middle of the periodic table; it is a solid semimetal.(c) Bismuth (Bi) is to the right, but below the semimetals in the periodic table, it is a solid metal.(d) Bromine (Br) is on the right side of the periodic table; it is a liquid nonmetal at normal conditions.

Solution

Indicate the physical state for each of the following elements at 25 °C and normal pressure; classify each element as a metal, nonmetal, or semimetal:(a) barium (b) boron(c) bismuth (d) bromine

Figure 4.5 Metals, Nonmetals, and Semimetals The symbols of elements having metallic properties are on the left side of the periodic table, nonmetallic are on the right side, and semimetallic are midway between. Notice the special placement of hydrogen, a nonmetallic element.

EXAMPLE EXERCISE 4.4 Physical States of the ElementsContinued

Figure 4.6 Physical States of the Elements At 25 °C and normal atmospheric pressure, all metals are in the solid state except Hg. Most nonmetals are gases except C, P, S, Se, and I, whichare solids. The only elements in the liquid state at normal conditions are Hg and Br.

Indicate the physical state for each of the following elements at 25 °C and normal pressure; classify each element as a metal, nonmetal, or semimetal:(a) aluminum (b) hydrogen(c) helium (d) radium

Practice Exercise

Answers: (a) solid metal; (b) gaseous nonmetal; (c) gaseous nonmetal; (d) solid metal

EXAMPLE EXERCISE 4.4 Physical States of the ElementsContinued

Which of the following is a liquid nonmetal under normal conditions: sodium, mercury, bromine, or sulfur? (Refer back to Figure 4.7.)

Concept Exercise


Figure 4.7 Pictorial Periodic Table of the Elements The natural abundance is the percent by mass of an element in Earth’s crust, oceans, and atmosphere. The natural abundance of an element listed as rare is less than 1 mg per metric ton (1000 kg). An element listed as synthetic is made artificially and does not occur naturally. An element listed as unstable often disintegrates in a fraction of a second.

EXAMPLE EXERCISE 4.5 Composition of Chemical Formulas

The chemical formula for vitamin B3 indicates 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and 1 oxygen atom. Thus C6H6N2O has a total of 15 atoms.

Solution

State the total number of atoms in a molecule of vitamin B3, C6H6N2O.

Answer: C8H11NO3 (total of 23 atoms)

Write the chemical formula for vitamin B6, if a molecule is composed of 8 carbon atoms, 11 hydrogen atoms, 1 nitrogen atom, and 3 oxygen atoms.

Practice Exercise

Examine the model for vitamin C and determine the molecular formula. In the model shown, the black sphere = C atom, white = H atom, and red = O atom.

Concept Exercise


EXAMPLE EXERCISE 4.6 Composition of Chemical Formulas

The chemical formula for glycerin indicates 3 carbon atoms, 5 hydrogen atoms, and 3 OH units. Thus, C3H5(OH)3 has a total of 14 atoms.

Solution

State the total number of atoms in a molecule of glycerin, C3H5(OH)3.

Answer: C3H5O3(NO2)3

Write the chemical formula for nitroglycerin if a molecule is composed of 3 carbon atoms, 5 hydrogen atoms, 3 oxygen atoms, and 3 NO2 units.

Practice Exercise

State the total number of atoms in a molecule of nitroglycerin, C3H5O3(NO2)3.

Concept Exercise


EXAMPLE EXERCISE 4.7 Physical and Chemical Properties

If a reaction occurs, there is a change in composition and the property is chemical. Otherwise, the property is physical.(a) Color and odor are physical properties.(b) Solubility is a physical property.(c) A chemical reaction is a chemical property.(d) A physical state is a physical property.

Solution

Classify each of the following properties as physical or chemical:(a) Water appears colorless and odorless at 20 °C.(b) Water dissolves sugar crystals.(c) Water produces a gas with calcium metal.(d) Water exists as ice at –10 °C.

Classify each of the following properties as physical or chemical:(a) Water appears hard and crystalline at 0 °C.(b) Water is insoluble in gasoline.(c) Water is a very weak conductor of electricity.(d) Water produces a gas with sodium metal.

Practice Exercise

Answers: (a) physical; (b) physical; (c) physical; (d) chemical

Copper melts at 1083 °C, has a density of 8.92 g/mL, is a good conductor of electricity, and turns black when heated. Which of these is an example of a chemical property?

Concept Exercise


EXAMPLE EXERCISE 4.8 Physical and Chemical Changes

An observation that indicates a physical change is a change of physical state. The observations that suggest a chemical change include burning, fizzing, changing color, or forming an insoluble substance in solution.(a) Hydrogen explodes; thus, it is a chemical change.(b) Water is boiled; thus, it is a physical change.(c) Two solutions give an insoluble substance; thus, it is a chemical change.(d) Baking soda fizzes; thus, it is a chemical change.

Solution

Classify each of the following observations as a physical or a chemical change:(a) Touching a lit candle to hydrogen soap bubbles gives an explosion.(b) Heating water in a flask produces moisture on the glass.(c) Combining two colorless solutions gives a yellow solid.(d) Pouring vinegar on baking soda produces gas bubbles.

Answers: (a) physical; (b) chemical; (c) chemical; (d) physical

Classify each of the following observations as a physical or a chemical change:(a) Freezing water in a refrigerator makes cubes of ice.(b) Adding silver nitrate to tap water gives a cloudy solution.(c) Burning sulfur gives a light blue flame.(d) Grinding aspirin tablets produces a powder.

Practice Exercise

EXAMPLE EXERCISE 4.8 Physical and Chemical ChangesContinued

An Alka-Seltzer tablet dissolves in water and produces gas bubbles. Is this an example of a physical change or a chemical change?

Concept Exercise


Alka-Seltzer An Alka-Seltzer tablet in water releases carbon dioxide gas bubbles.

EXAMPLE EXERCISE 4.9 Conservation of Mass Law

Applying the conservation of mass law, we find that the mass of the magnesium metal plus the mass of the oxygen gas equals the mass of the magnesium oxide powder. That is, 2.430 g Mg + mass of oxygen = 4.030 g MgO

mass of oxygen = 4.030 g MgO – 2.430 g Mgmass of oxygen = 1.600 g

Solution

In an experiment, 2.430 g of magnesium metal was ignited and burned with oxygen in the air. If 4.030 g of white magnesium oxide powder, MgO, was collected, what was the mass of oxygen gas that reacted?

Answer: 0.975 g

If 0.654 g of zinc metal reacts with 0.321 g of yellow powdered sulfur, what is the mass of the zinc sulfide produced?

Practice Exercise

Heating 1.000 g copper metal with yellow sulfur produces 1.252 g of black copper sulfide. What is the mass of sulfur that reacted with the copper metal?

Concept Exercise


EXAMPLE EXERCISE 4.10 Kinetic Energy and Molecular Motion

A steel cylinder containing air is heated from 25 °C to 50 °C. State the change in each of the following:(a) kinetic energy of the gas (b) motion of air molecules

Solution

A balloon filled with helium gas is cooled from 25 °C to –25 °C. State the change in each of the following:(a) kinetic energy of the gas (b) motion of helium atoms

Answers: (a) increases; (b) increases

Temperature, kinetic energy, and velocity are related as follows:(a) As the temperature cools from 25 °C to –25 °C, the kinetic energy of helium atoms decreases.(b) Since a drop in temperature produces a decrease in kinetic energy, the motion of helium atoms decreases.

Practice Exercise

What happens to the kinetic energy and velocity of air molecules when the temperature increases?

Concept Exercise


EXAMPLE EXERCISE 4.11 Forms of Energy

We can refer to the six forms of energy listed above. It follows that(a) Nuclear energy is converted to heat energy.(b) Heat energy is converted to mechanical energy.(c) Mechanical energy is converted to electrical energy.

Solution

Identify two forms of energy that are involved in each of the following conversions:(a) Radioactive emissions vaporize water to steam.(b) Steam drives a turbine.(c) A turbine spins and drives an electrical generator.

Answers: (a) chemical and light; (b) light and electrical; (c) chemical and electrical

Identify two forms of energy that are involved in each of the following devices:(a) flashlight(b) solar calculator(c) lead–acid battery

Practice Exercise

Which of the following is not a basic form of energy: chemical, electrical, heat, light, mechanical, nuclear, solar?

Concept Exercise


© 2011 Pearson Education, Inc.

The change from gas to solid is called

a. condensing.b. deposition.c. freezing.d. sublimation.


Air is an example of a(n)

a. compound.b. element.c. heterogeneous mixture.d. homogeneous mixture.


Ca is the symbol of the element

a. cadmium.b. calcium.c. californium.d. carbon.


Which is classified as a nonmetal?

a. Pb. Asc. Sbd. All of the above


How many atoms are in a molecule of trinitrotoluene, C7H5(NO2)3?

a. 3b. 4c. 15d. 21

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Example 1: Molecular Formula

Glucose contains 6 carbons, 12 hydrogens, and 6 oxygens. Write the molecular formula for glucose

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Example 2: Molecular Formula

List how many of each type of element the following compounds have

A) H2O

B) NH3

C) C2H4(OH)2

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Example 3: Conservation of Mass

C(s) + O2(g) CO2(g)

a) 12.3g C reacts with 32.8g O2, ?g CO2

b) 0.238g C reacts with ?g O2 to make .873g CO2

c) ?g C reacts with 1.63g O2 to make 2.24g CO2

Chapter 4 Matter and Energy Vanessa N. Prasad-Permaul CHM 1025 Valencia Community College 1.

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Transcript of Chapter 4 Matter and Energy Vanessa N. Prasad-Permaul CHM 1025 Valencia Community College 1.