Physical Science - Chapter 4 - Heat and Temperature

Converting Celsius to Fahrenheit

A bank temperature display indicates 20 degrees C (room temperature). What is the equivalent temperature on the Fahrenheit scale? Solution: TC = 20 degrees C TF = ? TF = 9/5TC + 32 degrees = 9/5 20 degrees + 32 degrees = 180 degrees/5 + 32 degrees = 36 degrees + 32 degrees = 68 degrees F

quad

A much larger unit is sometimes mentioned in news reports and articles about the national energy consumption. This unit is the quad, which is 1 quadrillion Btu (a million billion or 10(15) Btu).

Match the thermometers to how they work to measure the hotness or coldness of something.

Thermostat ----> Metals expand or contract in response to change. Glass bulb ----> A liquid expands in response to the highest reading. Modern medical ----> They measure infrared radiation emitted from the body.

The laws of thermodynamics

describe the relationships concerning what happens as energy is transformed to work and the reverse, also serving as useful intellectual tools in meteorology, chemistry, and biology.

Joule

The metric unit for measuring work, energy, or heat is the joule.

Phases of Matter

Three phases of matter are common on Earth under conditions of ordinary temperature and pressure. These phases--or forms of existence-- are solid, liquid, and gas. Each of these has a different molecular arrangement. The different characteristics of each phase can be attributed to the molecular arrangements and the strength of attraction between the molecules.

Your body judged temperature on the basis of the net direction of energy flow.

You sense situations in which heat is flowing into your body as warm and situations in which heat is flowing from your body as cool. Perhaps you have experienced having your hands in snow for some time, then washing your hands in cold water. The cold water feels warm. Your hands are colder than the water, energy flows into your hands, and they communicate "warm".

Kelvin Scale

a temperature scale that does not have arbitrarily assigned referent points, and zero means nothing; the zero point on the Kelvin scale (also called absolute scale) is the lowest limit of temperature, where all random kinetic energy of molecules ceases. The Kelvin scale was proposed in 1848 by William Thomson (1824-1907), who became Lord Kelvin in 1892. The zero point on the Kelvin scale is thought to be the lowest limit of temperature. Absolute zero is the lowest temperature possible, occurring when all random motion of molecules was historically projected to cease. Absolute zero is written as 0 K.

Gases

are composed of molecules with weak cohesive forces acting between them. The gas molecules are relatively far apart and move freely in a constant, random motion that is changed often by collisions with other molecules. Gases therefore have neither fixed shapes nor fixed volumes.

The pure substances hydrogen, oxygen, carbon, iron, and gold are chemical elements, and each has its own kind of properties

atom. In nature, some of these elements--carbon, iron, and gold--can exist as single atoms. Other elements, like hydrogen and oxygen, only exist as pure substances in mature when two of their atoms are tightly bound together.

Cohesion and adhesion are ______ forces between molecules, depending on whether the force is between like or unlike molecules, respectively.

attractive

Fill in the Blank Question Fill in the blank question. When considering the interaction of molecules, ______ is the attractive force between the same kind of molecules, whereas _______ is the attractive force between different kinds of molecules.

cohesion, adhesion

The kinetic molecular theory explains why matter generally expands with increased temperatures and

contracts with decreased temperatures.

the process of decreasing internal energy is called

cooling

The terms heating and cooling

describe the direction of energy flow, naturally moving from a region of higher energy to one of lower energy.

There are other distinctions between the phases of matter. The term vapor

is sometimes used to describe a gas that is usually in the liquid phase. Water vapor, for example, is the gaseous form of liquid water. Liquids and gases are collectively called fluids because of their ability to flow, a property that is lacking in most solids.

Calorie (cal)

is the metric unit of heat. A calorie is define as the amount of energy (or heat) needed to increase the temperature of 1 gram of water 1 degree Celsius. A more precise definition specifies the degree interval from 14.5 degrees C to 15.5 degrees C because the energy required varied slightly at different temperatures.

Condensation

is the opposite of evaporation. In evaporation, more molecules are leaving the liquid state than are returning. In condensation, more molecules are returning to the liquid state than are leaving. This is a dynamic, ongoing process with molecules leaving and returning continuously. The net number or returning determines whether evaporation or condensation is taking place.

Liquids do not have to be at the boiling point to change to a gas ang, in fact, tend to undergo a phase change at any temperature when left in the open. Although the phase change can occur at any temperature,

it occurs more rapidly at higher temperatures. The temperature of the water is associated with the average kinetic energy of the water molecules. The word average implies that some of the molecules have a greater energy and others have less.

A summary of the scientific assumptions about molecules and the space around them is provided by the ______ molecular theory.

kinetic

Converting Kelvin to Celsius

A science article refers to a temperature of 300.0K. What is the equivalent Celsius temperature? TK = 300.0K TC = ? TC = TK - 273 = 300.0 - 273 = 27 degrees C

Converting Kelvin to Fahrenheit

A science article refers to a temperature of 300.0K. What is the equivalent Fahrenheit temperature? TK = 300.0K TF = ? TF = 9/5 TC + 32 degrees TF = 9/5 27.0 degrees + 32 degrees TF = 243/5 + 32 degrees TF = 48.6 degrees + 32 degrees TF = 81 degrees F (It's really 80.6 degrees, but round up)

Substance and specific heat

Different materials require different amounts of heat to go through the same temperature range when their masses are equal. This property is called the specific heat of a material, which is define as the amount of heat needed to increase the temperate of 1 gram of substance 1 degree Celsius. The variable used to represent specific heat is c.

Which of the following best describes the relationship between the external and internal energy of an object?

External energy is the total potential and kinetic energy of the object; internal energy is the total potential and kinetic energy of the object's molecules.

Match each temperature scale to its appropriate description.

Fahrenheit ----> Water freezes at 32 degrees and boils at 212 degrees. Celsius ----> Water freezes at 0 degrees and boils at 100 degrees. Kelvin ----> Water freezes at 273 and boils at 373.

You can see the difference in heat and temperature by considering a cup of water and a large tub of water. If both the small and the large amount of water have the same temperature, both must have the same average molecular kinetic energy.

Now, suppose you wish to cool both by, say, 20 degrees. The large tub of water would take much longer to cool, so it must be that the large amount of water has more internal energy. Heat is a measure based on the total internal energy of the molecules of a body, and there is more total energy in a large tub of water than in a cup of water at the same temperature.

Kilocalorie (kcal)

One kilocalorie (kcal) is the amount of energy (or heat) needed to increase the temperature of 1 kilogram of water 1 degree Celsius. The measure of the energy released by the oxidation of food is the kilocalorie, but it is called the Calorie (with a capital C) by nutritionists. Confusion can be avoided by making sure that the scientific calorie is never capitalized (cal) and the dieter's Calorie is always capitalized. The best solution would be to call the Calorie what it is, a kilocalorie (kcal).

Atoms

One way to consider matter is in the form of the tiny, basic units of structure called atoms. The basic assumption of kinetic molecular theory is that all matter is made up of atoms.

How much heat must be supplied to a 500.0 g pan to raise its temperature from 20.0 degrees C to 100.0 degrees C if the pan is made of (a) iron and (b) aluminum?

Solution: (a) IRON: m = 500.0g c = 0.11cal/g degrees C Tf = 100.0 degrees C Q = ? Ti = 20.0 degrees C Q = mcΔT Q = (500.0 g) (0.11 cal/gCdegrees) (80.0C degrees) Q = (500.0)(0.11)(80.0)g X call/gCdegrees X C degrees Q = 4,400 cal Q = 4.4 kcal Solution: (b) aluminum m = 500.0 g c = 0.22 cal/gCdegrees Tf= 100.0Cdegrees Ti= 20.0degreesC Q = ? Q = mcΔT Q = (500.0 g) (0.22 cal/gCdegrees) (80.0C degrees) Q = (500.0)(0.22)(80.0)g X cal/gCdegrees X C degrees Q = 8,800 cal Q = 8.8 kcal It takes twice as much heat energy to warm the aluminum pan through the same temperature range as an iron pan. This, with equal rates of energy input, the iron pan will warm twice as fast as an aluminum pan.

A 1,000.0 kg car is moving at 90.0 km/h (25.0 m/s). How many kilocalories are generated when the car brakes to a stop?

Solution: The kinetic energy of the car is KE = 1/2 mv(2) KE = 1/2(1,000.0 kg)(25.0 m/s)2 KE = (500.0)(625) kg x m2/s2 KE = 312,500 J You can convert this to kcal by using the relationship between mechanical energy and heat: (312,500J) (1 kcal/4,184J) 312,500/4,184 J x Kcal/J 74.7 kcal Explanation: When a car brakes to a stop, the energy of the car's motion is converted into heat energy, which is dissipated by the brakes. The amount of heat energy generated is proportional to the kinetic energy of the car before braking. The formula to calculate the kinetic energy of an object is: KE = 1/2mv(2) where KE is the kinetic energy, m is the mass of the object, and v is the velocity of the object. Substituting the given values, we get: KE = 1/2 X 1000.0 kg x (25.o m/s)2 = 312, 500 J To convert this to kilocalories, we need to divide by 4.184, since 1 calorie is equal to 4.184 joules. Therefore, the energy generated when the car brakes to a stop is approximately 74.6 kilocalories.

Cohesion and Adhesion

Some molecules of solids and liquids interact, strongly attracting and clinging to one another. When this attractive force is between molecules of the same kind, it is called cohesion. It is a stronger cohesion that makes solids and liquids different from gases, and without cohesion, all matter would be in the form of gases. Sometimes one of a kind molecule attracts and clings to a different kind of molecule. The attractive force between unlike molecules is called adhesion. Water wets your skin because the adhesion of water molecules and skin is stronger than the cohesion of water molecules.

Adhesives

Some substances, such as glue, have a strong force of adhesion when they hard from a liquid state, and they are called adhesives.

Specific heat is responsible for the fact that air temperatures vary more over

land than over a large body of water. Since specific heat is defined as the amount of heat needed to increase the temperature of 1 gram of a substance 1 degree, this means 1 gram of water exposed to 1 calorie of sunlight will warm 1 degrees C. One gram of soil exposed to 1 calorie of sunlight, on the other hand will be warmed by 5 degrees C it only takes 0.2 calorie to warm the soil 1 degrees C. Thus, the temperature is more even near large bodies of water because it is harder to change the temperature of the water.

The molecules in a ______ flow over each other, yet are held together with relatively strong forces.

liquid

What phase of matter has a definite volume but not a definite shape? Multiple choice question.

liquid

What is the specific heat of a 2 kg metal sample if 1.2 kcal is needed to increase the temperature from 20.0 degrees C to 40.0 degrees C?

m = 2 kg Q = 1.2 kcal ΔT = 20 degrees Celsius C = ? Q = mcΔT c = Q/mΔT c = 1.2 kcal/(2 kg) (20.0Cdegrees) c = 1.2/(2)(20.0) kcal/kgCdegrees c = 0.03 kcal/kgCdegrees in simpler terms:

Scientists have developed a different type of thermometer and a way around the problems of using a glass mercury fever thermometer. This new approach

measures the internal core temperature by quickly reading infrared energy from the eardrum. All bodies with a temperature above absolute zero emit energy including your body. The intensity of the energy emitted is a sensitive function of body temperature, so reading the energy emitted will tell you about the temperature of that body.

Heat is energy in transit

not a material thing you can add or take away. Heat is understood to be a measure of internal energy that can be measured as energy flows into or out of an object.

All objects above absolute zero (0 K) emit radiant energy, but all

objects also absorb radiant energy. A hot object, however, emits more radiant energy that a cold object.

If a molecule of water that has an exceptionally high energy is near the surface and is headed in the right direction, it may

overcome the attractive forces of the other water molecules and escape the liquid to become a gas. This is the process of evaporation. Evaporation reduces a volume of liquid water as water molecules leave the liquid state to become water vapor in the atmosphere.

Humans usually judge temperature with their senses in a ______ manner. Assume no instruments are used.

relative

The molecules in a ______ are at regular distances from each other and are bound by relatively strong cohesive forces.

solid

The phase of matter that has a definite shape and volume is a(n) _______.

solid.

The _______ of a substance is a measure of the average kinetic energy of the molecules making up the substance.

temperature

There are four ways to increase the rate of evaporation:

1) An increase in the temperature of the liquid will increase the average kinetic energy of the molecules and thus increase the number of high-energy molecules able to escape from the liquid state. 2) Increasing the surface area of the liquid will also increase the likelihood of molecular escape to the air. This is why you spread out wet clothing to dry or spread out a puddle you want to evaporate. 3) Removal of water vapor from near the surface of the liquid will prevent the return of the vapor molecules to the liquid state and thus increase the net rate of evaporation. This is why thing dry more rapidly on a windy day. 4) Reducing the atmospheric pressure will increase the rate of evaporation. the atmospheric pressure and the intermolecular forces tend to hold water molecules in the liquid state. This, reducing the atmospheric pressure will reduce one of the forces holding molecules in a liquid state. Perhaps you have noticed that wet items dry more quickly at higher elevations, where the atmosphere pressure is less.

Matter is anything that has mass and occupies space. There are three states of matter:

1) Solid - have a fixed shape and volume. 2) Liquid - have a fixed volume but no fixed shape. 3) gas - have neither a fixed shape nor a fixed volume.

The process of heating is a transfer of energy involving:

1) a temperature difference or 2) energy-form conversions. Heat transfer that takes place because of a temperature difference takes place in three different ways: by conduction, convection, or radiation.

Solids, liquids, and gases are the three common phases of matter, and each phase is characterized by different molecular arrangements. The motion of the molecules in any of the three common phases can be increased by

1) adding heat through a temperature difference or 2) the absorption of one of the five forms of energy, which results in heating. In either case, the temperature of the solid, liquid, or gas increases according to the specific heat of the substance, and more heating generally means higher temperatures.

Heat is increased by an energy-form conversion, and the equivalence between energy and heating was first measured by James Joule. He found that the relationship between the energy form (mechanical, electrical radiant, etc.) and the resulting heating was always the same. For example, the relationship between mechanical work done and the resulting heating is always

4.184J = 1 cal or 4,184J = 1 kcal The establishment of this precise proportionality means that, fundamentally, mechanical work and heat are different forms of the same thing.

Molecules move (in simpler terms)

According to the kinetic molecular theory, gases are made up of tiny particles called molecules that are in constant motion. When you open a bottle of ammonia in an evenly heated room, the ammonia molecules leave the bottle and bounce around among the other molecules making up the air until they are everywhere in the room, slowly becoming more evenly distributed. This process is called diffusion. The ammonia odor diffuses throughout the room faster if the air temperature is higher and slower if the air temperature is lower. This is because the average kinetic energy of the ammonia molecules is proportional to the temperature of the air. The higher the temperature, the greater the average kinetic energy of the molecules, which means that they move faster and diffuse more quickly. Conversely, at lower temperatures, the average kinetic energy of the molecules is lower, so they move more slowly and diffuse more slowly. Rudolf Clausius formulated the relationship between the temperature of a gas and the motion of molecules in 1857. He showed that the temperature of a gas is proportional to the average kinetic energy of the gas molecules. This means that the average velocity of the ammonia molecules is greater at a higher temperature and slower at a lower temperature. It is important to note that kinetic energy involves the mass of the molecules as well as their velocity (KE = 1/2 mv²). Therefore, the average kinetic energy that is proportional to the temperature involves the molecular mass as well as the molecular velocity. Whether the kinetic energy is jiggling, vibrating, rotating, or moving from place to place, the temperature of a substance is a measure of the average kinetic energy of the molecules making up the substance.

What is the basic premise of the kinetic molecular theory?

All matter is made of atoms.

Kinetic Molecular Theory

All matter is made of molecules that move and interact.

At higher temperatures, the molecules of a substance move faster, with increased agitation; therefore, they move a little farther apart, thus expanding the substance.

As the substance cools, the motion slows, and the molecular forces are able to pull the molecules closer together, thus contracting the substance.

Match the word to its best description.

Atom ---> Basic unit of matter. Element ---> Simple, pure, substance made of atoms. Compound ---> Complex, pure substance made of atoms. Molecule ---> Tightly bound group of atoms that maintain the identity of the substance.

How do humans judge temperature without the use of instruments such as thermometers?

By sensing the flow of energy either into or away from their bodies.

Match the units of heat with their correction descriptions.

Calorie ----> Energy need to increase the temperature of 1 gram of water 1 degree Celsius. Kilocalorie ----> Energy need to increase the temperature of 1 kilogram of water 1 degree Celsius. British thermal unit ----> Energy need to increase the temperature of 1 pound of water 1 degree Fahrenheit.

Plasmas

Gases that are made up of positive ions and negative electrons are called plasmas. Plasmas have the same properties as gases but also conduct electricity and interact strongly with magnetic fields. Plasmas are found in fluorescent and neon lights on Earth, the Sun, and other stars. Nuclear fusion occurs in plasmas of stars, producing starlight as well as sunlight. Plasma physics is studied by scientists in their attempt to produce controlled nuclear fusion.

We can find the amount of heat needed to change a substance's temperature (Q) by multiplying the substance's specific heat by its mass and by the temperature change needed:

Q = mcΔT

Molecules Move

Suppose you are in an evenly heated room with no air currents. If you open a bottle of ammonia, the odor of ammonia is soon noticeable everywhere in the room. According to the kinetic molecular theory, molecules of ammonia leave the bottle and bounce around among the other molecules making up the air until they are everywhere in the room, slowly becoming more evenly distributed. The ammonia molecules diffuse, or spread, throughout the room. The ammonia odor diffuses throughout the room faster if the air temperature is higher and slower if the air temperature is lower. This would imply a relationship between the temperature and the speed at which molecules move about. The relationship between the temperature of a gas and the motion of molecules was formulated in 1857 by Rudolf Clausius. He showed that the temperature of a gas is proportional to the average kinetic energy of the gas molecules. This means that ammonia molecules have a greater average velocity at a higher temperature and a slower average velocity at a lower temperature. This explains why gases diffuse at a greater rate at higher temperatures. Recall, however, that kinetic energy involves the mass of the molecules as well as their velocity (KE = 1/2 mv2) . It is the average kinetic energy that is proportional to the temperature, which involves the molecular mass as well as the molecular velocity. Whether the kinetic energy is jiggling, vibrating, rotating, or moving from place to place, the temperature of a substance is a measure of the average kinetic energy of the molecules making up the substance.

Converting Fahrenheit to Celsius

The average human body temperature is 98.6 degrees F. What is the equivalent temperature on the Celsius scale? Solution: TF = 98.6 degrees F TC = 5/9(TF - 32 degrees C) = 5/9(98.6 degrees F - 32 degrees C) = 5/9 (66.6 degrees) = 333 degrees/9 = 37 degrees C

Thermodynamics

The branch of physical science called thermodynamics is concerned with the study of heat and its relationship to mechanical energy, including the science of heat pumps, heat engines, and the transformation of energy in all its forms.

When you push a table across the floor, the observable external kinetic energy of the table is transferred to the internal kinetic energy of the molecules between the table legs and the floor, resulting in a temperature increase.

The relationship between external and internal kinetic energy explains why the heating is proportional to the amount of mechanical energy used.

Drying closes on a clothes line....

There are four factors that will influence the time needed to dry these clothes. 1) Temperature. Higher temperature means higher kinetic energy water molecules that can more easily escape. 2) Surface area. Spreading the clothes increases the surface area exposed to the atmosphere, and more water molecules can escape from an increase surface area. 3) Wind. Wind will remove evaporated water molecules so they cannot return to the clothes. 4) Altitude. Higher altitude has less atmospheric pressure and therefore allows water vapor to more easily escape.

Two Heating Methods

There are two general ways that heating can occur. These are: 1) from a temperature difference, with energy moving from the region of higher temperature, and 2) from an object gaining energy by way of an energy-form conversion.

Temperature difference

When a temperature difference occurs, energy is transferred from a region of higher temperature to a region of lower temperature.

Cohesion and Adhesion (in simpler terms)

When we talk about matter, we are referring to anything that has mass and takes up space. Matter can exist in three different states: solid, liquid, and gas. In solids and liquids, the molecules are very close together and interact with each other through cohesion. Cohesion is the force that holds molecules of the same kind together. In solids, the molecules are held together so tightly that they cannot move around, which is why solids have a fixed shape. In liquids, the molecules are still close together, but they can move around and take the shape of their container. Gases, on the other hand, are very different from solids and liquids. The molecules in gases are very far apart and do not interact with each other through cohesion. Instead, they move around freely and take the shape of their container. Sometimes, molecules of different kinds can interact with each other through adhesion. Adhesion is the force that holds molecules of different kinds together. For example, when you touch water, the water molecules are attracted to your skin through adhesion. This is why water wets your skin. The adhesion between the water molecules and your skin is stronger than the cohesion between the water molecules, which allows the water to spread out and wet your skin. So, in summary, solids and liquids are different from gases because they have stronger cohesion between their molecules. This cohesion is what gives solids and liquids their fixed shape and volume. When molecules of different kinds interact with each other through adhesion, they can form new substances or change the properties of existing substances.

Specific Heat

each subject has its own specific heat, which is defined as the amount of energy (or heat) needed to increase the temperature of 1 gram of substance 1 degree Celsius. You can observe a relationship between heat and different substances by doing an experiment in "kitchen physics" Imagine that you have a large pot of liquid to boil in preparing a meal. Three variables influence how much heat you need: 1) The initial temperature of the liquid; 2) How much liquid is in the pot; and, 3) The nature of the liquid (water or soup?). What this means specifically is 1) Temperature change. It takes more heat to raise the temperature of the water more degrees. The amount of heat needed to table a substance's temperature is proportional to the temperature change, so this relationship could be written as Q ∝ ΔT. 2) Mass. A larger mass requires more heat to go through the same temperature change than a smaller mass. The amount of heat needed is also proportional to the amount of the substance being heated. In symbols, this can be written as Q ∝ m. 3) Substance. Different materials require amounts of heat to go through the same temperature range when their masses are equal. This property is called the specific heat of a material which is defined as the amount of heat needed to increase the temperature of 1 gram of a substance 1 degree Celsius. The variable use to represent specific heat is c.

Multiple Choice Question Oxygen is an example of a(n) ______, whereas water (H2O) is an example of a(n) ______. Both are composed of atoms, and both can be considered molecules.

element; compound

Oxygen is an example of a(n) ______, whereas water (H2O) is an example of a(n) ______. Both are composed of atoms, and both can be considered molecules.

element; compound

To distinguish between the energy of the object and the energy of its molecules, we use the terms

external and internal energy.

Atoms are made of

extremely small particles. These extremely small particles are arranged in specific ways, and each unique combination is known as an element. All atoms of any chemical are identical. For example, all atoms of oxygen contain eight tiny particles known as protons.

The Calorie value of food is determined by measuring the heat released

from burning the food. For example, if there is 10.0 kg of water and the temperature increased from 10 degrees to 20 degrees C, the food contained 100 Calories (100,000 calories). The food illustrated here would release much more energy than this.

molecule

from the chemical point of view, a particle composed of two or more atoms held together by an attractive force called a chemical bond; from the kinetic theory point of view, the smallest particle of a compound or gaseous element that can exist and still retain the characteristic properties of a substance.

The molecules in a ______ are held together with weak forces that allow them to move constantly and randomly.

gas

The phase of matter that has neither a definite volume nor a definite shape is a(n)______.

gas

Solids

have definite shapes and volumes because they have molecules that are nearly fixed distances apart and bound by relatively strong cohesive forces. Each molecule is a nearly fixed distance from the next, but it does vibrate and move around an equilibrium position. The masses of these molecules and the spacing between them determine the density of the solid. The hardness of a solid is the resistance of a solid to forces that tend to push its molecules farther apart.

Heat

is based on the total internal energy of the molecules of a body. (In comparison, temperature is a measure of the degree of hotness or coldness of a body, a measure that is based on the average molecular kinetic energy.)

Water molecules that evaporate move about in all directions, and some will return, striking the liquid surface. The same forces that they escaped from earlier capture the molecules, returning them to the liquid state. This is called

the process of condensation.

Liquids

have molecules that are not confined to a equilibrium position as in a solid. The molecules of a liquid are close together and bound by cohesive forces that are not as strong as in a solid. This permits the molecules to move from place to place within the liquid. The molecular forces are strong enough to give the liquid a definite volume but not strong enough to give it a definite shape. Thus, a liter of water is always a liter of water (unless it is under tremendous pressure), and it takes the shape of the container holding it. Because the forces between the molecules of a liquid are weaker than the forces between the molecules of a solid, a liquid cannot support the stress of a rock placed on it as a solid does. The liquid molecules flow, rolling over one another as the rock pushes its way between the molecules. Yet, the molecular forces are strong enough to hold the liquid together, so it keeps the same volume.

The measure of the internal energy that has been absorbed or transferred from one object to another is ______ .

heat

The process of increasing the internal energy is called

heating

Some substances exist as gases at ordinary temperatures, such as oxygen and carbon dioxide. Other substances, like water and mercury metal, exist as liquids at ordinary temperatures. Most metals exist as solids at ordinary temperatures. However,

if we increase the temperature of a substance enough, it will eventually become a gas. This is because heat energy causes the particles in a substance to move faster and farther apart from each other. At a certain temperature, the particles will be moving so fast that they will break from each other and become a gas. So, in summary, some substances exist as gases at ordinary temperatures, while others exist as liquids or solids. However, if we increase the temperature enough, all substances will become gases.

Scientists have developed a different type of thermometer that measures the internal core temperature by quickly reading ______ energy from the eardrum.

infrared

Specific Heat is related to the

internal structure of a substance. In any temperature change, some of the energy goes into the internal potential energy of the molecules, and some goes into the internal kinetic energy of the molecules. Because every substance has a unique internal molecular structure, each substance absorbs energy in a unique way, resulting in a unique value for specific heat. The difference in values for the specific heat of different substances is related to the number of molecules in a 1-gram sample of each and to the way they form a molecular structure.

Heat Engine

is a device that converts heat into mechanical energy. First, this cylinder traps a sample of air. The piston is like a slightly smaller cylinder and has a weight resting on it, supported by the trapped air. Then, if the air in the large cylinder is now heated, the gas molecules will acquire more kinetic energy. This results in more gas molecule impacts with the enclosing surfaces, which results in an increases pressure. Increased pressure results in a net force, and finally the piston and weight move upward. Thus, some of the heat has now been transformed to the increased gravitational potential energy of the weight.

Heat

is a measure of internal energy that has been transferred or absorbed. How can we measure heat? Since it is difficult to see molecules, internal energy is difficult to measure directly. Thus heat is nearly always measured during the process of a body gaining or losing energy. This measurement procedure will also give us a working definition of heat.

Diatomic molecule

is a molecule compose of only two atoms of the same or different chemical elements.

Nuclear Fusion

is a process in which two or more atomic nuclei combine to form a single, more massive nucleus. This process releases a large amount of energy and is the same process that powers the sun and other stars.

Element

is a pure substance that cannot be broken down into any other substances by ordinary chemical processes. Each element is made up of one type of atom, which has a unique number of protons in its nucleus.

Compound

is a unique substance that forms when two or more elements combine chemically. The elements in compounds are held together by chemical bonds. A chemical bond is a force of attraction between atoms or ions that share or transfer valence electrons. (Book definition ->) In addition to the chemical elements, there are pure substances called compounds that have more complex units of structure. Pure substances, such as water, sugar, and alcohol, are composed of atoms of two or more elements that join together in definite proportions. Water, for example, has structural units that are made up of two atoms of hydrogen tightly bound to one atom of oxygen (H20). These units are not easily broken apart. Each unit is the smallest unit of water that can exist. A molecule is generally defined as a tightly bound group of atoms that retains the chemical and physical properties of that substance.

Phase change

the action of a substance changing from one state of matter to another; a phase change always absorbs or releases internal potential energy that is not associated with temperature change. When a solid, liquid, or gas changes from one phase to another, the transition is called a phase change. A phase change always absorbs or releases a quantity of heat that is not associated with a temperature change. Since the quantity of heat associated with a phase change is not associated with temperature change, it is called latent heat. Latent heat refers to the hidden energy phase changes, which is energy (heat) that foes into or comes out of internal potential energy.

British thermal unit (Btu)

the amount of energy or heat needed to increase the temperature of 1 pound of water 1 degree Fahrenheit (abbreviated Btu). The English system's measure of heating is called the British thermal unit (Btu). The Btu us commonly used to measure the heating or cooling rates of furnaces, air conditioners, water heaters, and so forth. The rate is usually expressed or understood to be in Btu per hour.

Multiple Choice Question While the word temperature is commonly used to describe how hot or cold something is, in terms of the kinetic molecular theory, temperature is ________.

the measure of the average kinetic energy molecules in a substance.

The Celsius Scale

the referent scale that defines numerical values for measuring hotness or coldness, defined as degrees of temperature; based on the reference points of the freezing point of water and the boiling point of water at sea-level pressure, with 100 degrees between the two points. It was invented by Anders C. Celsius (1701-1744), a Swedish astronomer, in about 1735. The Celsius scale identifies the freezing point of water as 0 degrees Celsius and the boiling point as 100 degrees Celsius. There are 100 equal intervals, or degrees, between these two reference points, so the Celsius scale is sometimes called the centigrade scale.

The Fahrenheit Scale

the referent scale that defines numerical values for measuring hotness or coldness, defined as degrees of temperature; based on the reference points of the freezing point of water and the boiling point of water at sea-level pressure, with 180 degrees between the two points. It was developed by the German physicist Gabriel D. Fahrenheit (1686-1736) in about 1715. 32 degrees F (freezing point of water) and 212 degrees F (boiling point of water under normal pressure) are the reference points.

Radiation

the transfer of heat from a region of higher temperature to a region of lower temperature by greater emission of radiant energy from the region of higher temperature. Radiation involves the form of energy called radiant energy, energy that moves through space.

Conduction

the transfer of heat from a region of higher temperature to a region of lower temperature by increased kinetic energy moving from molecule to molecule.

Convection

the transfer of heat from a region of higher temperature to a region of lower temperature by the displacement of high-energy molecules--for example, the displacement of warmer, less dense air (higher kinetic energy) by cooler, denser air (lower kinetic energy).

External energy is the

total potential and kinetic energy of an everyday-sized object.

Internal energy

us the total kinetic and potential energy of the molecules of an object. The kinetic energy of a molecule can be much more complicated than straight-line velocity might suggest, however, because a molecule can have many different types of motion at the same time (pulsing, twisting, turning, etc.) Overall, internal energy is characterized by properties such as temperature, density, heat, volume, pressure of a gas, and so forth.