matter and energy - chemistry department -...

Chapter 3

▪The Periodic Table of the Elements

▪3.1 - Classification of Matter

▪3.2 – States and Properties of Matter

▪3.3 – Temperature

▪3.4 – Energy

▪3.5 – Energy and Nutrition

▪3.6 – Specific Heat

▪3.7 – Changes of State

▪Atoms are the building blocks from which all other things are built.

Just like Legos can be used to build endless creations…

… everything in the universe is built of different combinations of atoms

▪There are (roughly)118 different types of atoms.▪ Think of it as 118 different colors of Legos.

▪Each type of atom is called an element.

Sulfur Aluminum Mercury Carbon

▪3.4 – Energy

Classify examples of matter as pure substances or mixtures.

▪Is the material that makes up all things.

▪Is anything that has mass and takes up space.

Different types of matter

are categorized by what

they are made of.

Pure Substances or Mixtures

Matter is classified according to its composition.

▪Pure substances have a fixed or definite composition.

▪Mixtures contain two or more different substances that are physically mixed but not chemically combined.

Elements and Compounds

A pure substance is:▪ A type of matter with a fixed or definite composition.

▪ An element that is composed of one type of atom.

▪ A compound (molecule) that is composed of two or more elements always combined in the same proportion.

An aluminum can

consists of many atoms

of aluminum.

Elements

▪Elements are pure substances that contain one type of material, such as the following:

▪ Copper, Cu

▪ Lead, Pb

▪ Aluminum, Al

Elements

A compound contains two or more elements in a definite ratio, such as the following:

▪hydrogen peroxide (H2O2)

▪table salt (NaCl)

▪sugar (C12H22O11)

▪water (H2O)

Elements:

Red: Oxygen

White: Hydrogen

A mixture is a type of matter that consists of

▪ two or more substances that are physically mixed but not chemically combined.

▪ two or more substances in different proportions.

▪substances that can be separated by physical methods.

▪Two types: heterogeneous or homogeneous

Homogeneous

In a homogeneous mixture,

▪ the composition is uniform throughout.

▪ the different parts of the mixture are not visible.

Scuba Breathing Mixtures

Breathing mixtures for scuba diving are homogeneous mixtures. Some examples are the following:

▪nitrox (oxygen and nitrogen gases)

▪heliox (oxygen and helium gases)

▪ trimix (oxygen, helium, and nitrogen gases)

Heterogeneous

In a heterogeneous mixture,

▪ the composition varies from one part of the mixture to another.

▪ the different parts of the mixture are visible.

Identify each of the following as a pure substance or mixture:

A. pasta and tomato sauce

B. aluminum foil

C. helium

D. air

Identify each of the following as a homogeneous or heterogeneous mixture:

A. hot fudge sundae

B. shampoo

C. sugar water

D. peach pie

▪3.4 – Energy

Identify the states and the physical and chemical properties of matter.

▪On Earth, matter exists in one of three physical forms called the states of matter.

Solids have

▪ a definite shape.

▪ a definite volume.

▪ particles that are close together in a rigid pattern

▪ particles that move only by vibrating slowly.

A solid has a definite shape and volume.

Amethyst, a solid, is a purple

form of quartz (SiO2).

Think of atoms and molecules as tiny little magnets.

Liquids have

▪an indefinite shape but a definite volume.

▪particles that are close together but mobile.

▪particles that move slowly.

A liquid has a definite volume but takes the shape of its container.

Gases have

▪an indefinite shape.

▪an indefinite volume.

▪ the same shape and volume as their container.

▪particles that are far apart.

▪particles that move very fast.

A gas takes the shape and volume of its container.

Identify each description as that of a solid, liquid, or gas.

A. It has definite volume but takes the shape of thecontainer.

B. Its particles are moving rapidly.

C. Its particles fill the entire volume of a container.

D. Its particles have a fixed arrangement.

E. Its particles are close together but moving randomly.

Identify the state of matter for each of the following:

A. vitamin tablets

B. eye drops

C. vegetable oil

D. a candle

E. air in a tire

▪are characteristics observed or measured without changing the identity of a substance.

▪include shape, physical state (gas, liquid, solid), boiling and freezing points, density, and color of the substance.

Copper

Copper has these physical properties:

▪ reddish-orange color

▪shiny

▪excellent conductor of heat and electricity

▪solid at 25 °C

▪melting point 1083 °C (liquid → solid)

▪boiling point 2567 °C (liquid → gas) Copper, used in cookware, is

a good conductor of heat.

All of these properties can be measured without

changing copper into something else that isn’t copper

A physical change occurs in a substance if there is

• a change in the state.

• a change in the physical shape.

• no change in the identity and composition of the substance.

The evaporation of water

from seawater gives white,

solid crystals of salt called

sodium chloride.

A physical change occurs in a substance if there is

• a change in the state.

• a change in the physical shape.

• no change in the identity and composition of the substance.

Classify each of the following physical changes as a change of state or change of shape:

A. chopping a log into kindling wood

B. water boiling in a pot

C. ice cream melting

D. ice forming in a freezer

E. cutting dough into strips

Chemical properties describe the ability of a substance

▪ to interact with other substances.

▪ to change into a new substance.

When a chemical change takes place, the original substance is turned into one or more new substances with new chemical and physical properties.

During a chemical change,

a new substance forms that

• a new composition.

• new chemical properties.

• new physical properties.

Sugar caramelizing at a high

temperature is an example

of a chemical change.

Flan has a topping of caramelized

sugar.

During a chemical change,

a new substance forms that

• a new composition.

• new chemical properties.

• new physical properties.

Classify each of the following properties as physical or chemical:

A. Ice melts in the sun.

B. Copper is a shiny metal.

C. Paper can burn.

D. A silver knife can tarnish.

E. A magnet removes iron particles from a mixture.

Classify each of the following changes as physical or chemical:

A. burning a candle

B. ice melting on the street

C. toasting a marshmallow

D. cutting a pizza

E. iron rusting in an old car

▪3.4 – Energy

Convert between Fahrenheit, Celsius, and Kelvin

▪ is a measure of how hot or cold an object is compared to another object.

▪ indicates the heat flow from the object with a higher temperature to the object with a lower temperature.

▪ is measured using a thermometer.

Fahrenheit and Celsius

The temperature scales are Fahrenheit (°F) and Celsius (°C).

▪ The temperature difference between boiling and freezing of water are divided into smaller units called degrees.

▪ On the Celsius scale, there are 100 degrees between the boiling and freezing points of water.

▪ On the Fahrenheit scale, there are 180 degrees between the boiling and freezing points of water.

Kelvin

Scientists have learned that the coldest temperature possible is −273 °C. On the Kelvin scale, this is called

absolute zero and is represented as 0 K.

The Kelvin scale has

• units called kelvins (K).

• no degree symbol in front of K to represent temperature.

• no negative temperatures.

• the same size units as Celsius: 1 K = 1 °C.

A comparison of the Fahrenheit, Celsius, and Kelvin temperature scales between the freezing and boiling points of water.

A. What is the temperature at which water freezes?

1) 0 °F 2) 0 °C 3) 0 K

B. What is the temperature at which water boils?

1) 100 °F 2) 32 °F 3) 373 K

C. How many Celsius units are between the boiling and

freezing points of water?

1) 100 2) 180 3) 273

To convert temperatures between the Celsius and Fahrenheit

scales, we adjust for the size of the degrees. There are

▪100 degrees Celsius between the freezing and boiling points of

water.

▪180 degrees Fahrenheit between the freezing and boiling points

of water.

Therefore, 180 degrees Fahrenheit = 100 degrees Celsius

Adjusting for the different freezing points, 0 °C and 32 °F, we can write temperature equations to convert between Fahrenheit and Celsius temperatures.

TF = Temperature Fahrenheit

TC = Temperature Celsius

Step 1: State the given and needed quantities.

Step 2: Write a temperature equation.

𝑇𝐹 = 1.8 𝑇𝐶 + 32

Step 3: Substitute in the known values and calculate the new temperature.

A person with hypothermia has a body temperature of 34.8°C. What is that temperature in degrees Fahrenheit?

𝑇𝐹 = 1.8 𝑇𝐶 + 32

On a cold winter day, the temperature is –15 °F. What is that temperature in degrees Celsius?

A. −85 °C

B. −47 °C

C. −42 °C

D. −26 °C

Step 2: Write a temperature equation.𝑇𝐹 = 1.8 𝑇𝐶 + 32

TK = TC + 273

TK = Temperature Kelvin

What is the normal body temperature, 37 °C, in kelvins?

A. 236 K

B. 310. K

C. 342 K

D. 98.0 K

𝑇𝐹 = 1.8 𝑇𝐶 + 32 or 𝑇𝐾 = 𝑇𝐶 + 273

▪3.4 – Energy

Identify energy as potential or kinetic.Convert between units of energy.

▪ makes objects move.

▪ makes things stop.

▪ is defined as the ability to do work.

A defibrillator provides electrical

energy to heart muscle to re-

establish normal rhythm.

Kinetic energy is the energy of motion.

Examples are the following:

• swimming

• water flowing over a dam

• working out

The movement of water that flows from the

top of a dam is an example of kinetic energy.

Potential energy is energy stored for use at a later time.

Examples are the following:

▪water at the top of a dam

▪a compressed spring

▪chemical bonds in gasoline, coal, or food

▪a full battery

The water at the top of a dam has potential energy by virtue of its position. As the water falls over and down the dam, the potential energy is converted to kinetic energy.

Identify the energy in each example as potential or kinetic:

A. rollerblading

B. a peanut butter and jelly sandwich

C. mowing the lawn

D. gasoline in the gas tank

Heat is the energy associated with the movement of particles.

The faster the particles move, the greater the heat or thermal energy of the substance.

Given an ice cube, as heat is added, the H2O molecules

▪ that are moving slowly increase their motion.

▪eventually have enough energy to change the ice cube from a solid to a liquid.

Energy is measured in

▪ the SI unit, the joule (J), or in kilojoules (kJ), 1000 joules.

▪ units of calories (cal) or in kilocalories (kcal), 1000 calories.

The calorie is defined as the amount of energy needed to raise the temperature of 1 g of water by 1 °C.

How many calories are obtained from a pat of butter if it provides 150 J of energy when metabolized?

A. 0.86 cal

B. 630 cal

C. 36 cal

Step 1: State the given and

needed quantities (units).

Step 2: Write a plan to convert the

given unit to the needed unit.

Step 3: State the equalities

and conversion factors

Step 4: Set up the problem to cancel

units and calculate the answer.

How many joules are obtained from an apple if it provides 90 calsof energy when metabolized?

Step 1: State the given and

needed quantities (units).

Step 2: Write a plan to convert the

given unit to the needed unit.

Step 3: State the equalities

and conversion factors

Step 4: Set up the problem to cancel

units and calculate the answer.

▪3.4 – Energy

Use the energy values to calculate the kilocalories (kcal) and kilojoules (kJ) for food.

▪ Your body uses calories for energy.

▪ “Calorie” is a unit of energy.

Question: Where do the calorie counts on food labels come from? How do we know how many calories something has?

Answer: Nutritionists light the food on fire!

Nutritionists burn food in a calorimeter that

▪consists of a steel container filled with oxygen and a measured amount of water.

▪ indicates the heat gained by water, which is the heat lost by a sample during combustion.

▪ In a calorimeter, the burning of a food sample increases the temperature of the water, which is used to calculate the energy value of the food.

On food labels, energy is shown as the nutritional Calorie, written with a capital C. In countries other than the United States, energy is shown in kilojoules (kJ).

1 Cal = 1000 calories

1 Cal = 1 kcal

We will largely use “kcal” in this class. But remember, kcal is what you are used to.

The caloric or energyvalue for 1 g of a foodis given in kilojoules (kJ) or kilocalories (kcal).

The typical energy values are different for each food type.

Remember: 1 Cal = 1 kcal

A cup of whole milk contains 13 g of carbohydrate, 9.0 g of fat, and 9.0 g of protein. How many kilocalories does a cup of whole milk contain?

A That’s it. fruit bar contains 28 g of carbohydrate, 0 g of fat, and 1.0 g of protein. How many kilocalories does my snack contain?

▪3.4 – Energy

Use specific heat to calculate heat loss or gain.

▪ Every substance has its own characteristic ability to absorb heat.

▪ Certain substances must absorb more heat than others to reach a certain temperature.

▪ The energy requirements for different substances are described in terms of a physical property called specific heat (SH).

▪ Definition: the amount of heat that raises the temperature of exactly 1g of a substance by exactly 1°C

▪ Specific heat is given as a number with the units J/g°C (or cal/g°C)

The high specific heat of

water keeps temperature

more moderate in

summer and winter.

SH of water = 1.00 cal/g°C

= 4.18 J/g°C

If you add 1.00 cal of heat to:

1 g of water, temp increases 1°C

1 g of aluminum, temp increases by 5°C

1 g of copper, temp increases by 10°C

The low specific heats of aluminum and

copper means they transfer heat efficiently,

which make them useful in cookware.

1. When ocean water cools, the surrounding air

A. cools. B. warms. C. stays the same.

2. Sand in the desert is hot in the day and cool at night. Sand must have a

A. high specific heat. B. low specific heat.

▪ When we know the specific heat of a substance, we can

• calculate the heat lost or gained, by measuring its mass and temperature change.

What is the specific heat if 24.8 g of a metal absorbs

275 J of energy and the temperature rises from 20.2 °C

to 24.5 °C?

What is the mass in grams of a metal that has a specific

heat of 0.385 J/g°C, absorbs 320 J of energy and the

temperature rises from 26.7 °C to 115 °C?

▪3.4 – Energy

Describe the changes of state between solids, liquids, and gases; calculate the energy involved.

Matter undergoes a change of statewhen it is converted from one state (solid, liquid, or gas) to another state.

▪ When heat is added to a solid, the particles move faster

▪ At a certain temperature, the particles have enough energy tobreak free of the attraction with their neighbors and move randomly.▪ This is melting (solid → liquid)

▪ Temperature = melting point

▪ If the temperature of a liquid is lowered, (kinetic) energy is lost, slowing theparticles down.

▪ The attractive forces of their neighbors pull the particles close together

▪ This is freezing

▪ Temperature = freezing point

▪ Every substance as its own meeting/freezing point.

Water melts at 0°C, freezes at 0°CGold melts at 1064°C, freezes at 1064°C

Melting requires heat!

Freezing releases heat!

Heat of Fusion

The heat of fusion

▪ is the amount of heat released when 1 g of liquid freezes (at its freezing point).

▪ is the amount of heat needed to melt 1 g of solid (at its melting point).

For a given amount of substance,

heat released during freezing = heat needed during melting

Heat of Fusion

Heat of Fusion for Water = 80 cal/g (or 334 J/g)

To melt water,

To freeze water,

How many joules are needed to melt 32.0 g of ice at 0 °C?

(Water’s Heat of Fusion: 334 J/g)

The heat of fusion can be used as a conversion factor.

▪ Evaporation (vaporization) is taking place as molecules with sufficient energy escape from the liquid surface and enter the gas phase.

▪ liquid → gas

▪ Temperature = boiling point

The higher the heat, the faster molecules

gain enough energy to escape to gas. water in a mud puddle disappears

▪ The reverse of evaporation, when heat is removed, is condensation.

▪ water vapor is converted back to liquid as the water molecules cool down and lose energy and speed.

Condensation temperature = boiling point

Example: condensation on mirror

When sublimation occurs,

▪ the particles on the surface of the solid change directly to a vapor.

▪ there is no change in temperature.

When deposition occurs, gas particles change directly to a solid.

▪ Dry ice undergoes sublimation at –78 °C.

Sublimation and deposition are

reversible processes.

Dry ice sublimes at –78 °C.

Sublimation Deposition

The heat of vaporization is the amount of heat

• absorbed to change 1 g of liquid to gas at the boiling point.

• released when 1 g of gas changes to liquid at the boiling point.

▪ The heat of vaporization for water (boiling point 100 °C) is the heat absorbed when 1 g of water changes to steam.

▪ The heat of condensation for water is the heat released when 1 g of steam changes to water.

How many kilojoules (kJ) are released when 50.0 g of steam from a volcano condenses at 100 °C?

On a heating/cooling

curve, diagonal lines

indicate changes in

temperature for a

physical state, and

horizontal lines

(plateaus) indicate

changes of state.

1. A plateau (horizontal line) on a heating curve represents

A. a temperature change.

B. a constant temperature.

C. a change of state.

2. A sloped line on a heating curve represents

A. a temperature change.

B. a constant temperature.

C. a change of state.

Use the cooling curve for water to answer each of the following:

1. Water condenses at a temperature ofA. 0 °C. B. 50 °C. C. 100 °C.

2. At a temperature of 0 °C, liquid water

A. freezes. B. melts. C. changes to a gas.3. At 40 °C, water is a

A. solid. B. liquid. C. gas.

4. When water freezes, heat isA. removed. B. added.

Calculate the total heat, in joules, needed to convert 15.0 g of liquid ethanol at 25.0 °C to gas at its boiling point of 78.0 °C. Ethanol has a specific heat of 2.46 J/g °C and a heat of vaporization of 841 J/g.

Step 2: Write a plan to convert given to needed.

Step 3: Write the heat conversion factor and any

metric factors.

Step 4: Set up the problem and calculate.

When a volcano erupts, 175 g of steam at 100.0 °C is released. How many kilojoules are lost when the steam condenses, then freezes, at 0.0 °C?

Step 2: Write a plan to convert given to needed.

Step 3: Write the heat conversion factor and any

metric factors.

Step 4: Set up the problem and calculate.

matter and energy - chemistry department -...

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