Chapter States and Properties of Matter. The Periodic Table of the Elements Classification of Matter. 3.5 Energy and Nutrition

Transcription

1 Chapter 3 Atoms are the building blocks from which all other things are built. The Periodic Table of the Elements 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 Just like Legos can be used to build endless creations everything in the universe is built of different combinations of atoms

2 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 The Periodic Table of the Elements 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

3 Classify examples of matter as pure substances or mixtures. 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. 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. 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.

4 Elements Elements are pure substances that contain one type of material, such as the following: Copper, Cu Lead, Pb Aluminum, Al 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 Elements A compound contains two or more elements in a definite ratio, such as the following: hydrogen peroxide (H 2 O 2 ) table salt (NaCl) sugar (C 12 H 22 O 11 ) water (H 2 O) Homogeneous In a homogeneous mixture, the composition is uniform throughout. the different parts of the mixture are not visible. Elements: Red: Oxygen White: Hydrogen

5 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

6 Identify each of the following as a homogeneous or heterogeneous mixture: A. hot fudge sundae B. shampoo C. sugar water D. peach pie Identify the states and the physical and chemical properties of matter. The Periodic Table of the Elements 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 On Earth, matter exists in one of three physical forms called the states of matter.

7 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. 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. Think of atoms and molecules as tiny little magnets. Amethyst, a solid, is a purple form of quartz (SiO 2 ). 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.

8 Identify each description as that of a solid, liquid, or gas. A. It has definite volume but takes the shape of the container. 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. 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. 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 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

9 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. 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 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. 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.

10 During a chemical change, a new substance forms that has 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. 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. During a chemical change, a new substance forms that has a new composition. new chemical properties. new physical properties. 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

11 The Periodic Table of the Elements 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 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. Convert between Fahrenheit, Celsius, and Kelvin 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.

12 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

13 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 Step 1: State the given and needed quantities. Step 2: Write a temperature equation. = Step 3: Substitute in the known values and calculate the new temperature. Adjusting for the different freezing points, 0 C and 32 F, we can write temperature equations to convert between Fahrenheit and Celsius temperatures. T F = Temperature Fahrenheit T C = Temperature Celsius A person with hypothermia has a body temperature of 34.8 C. What is that temperature in degrees Fahrenheit? Step 1: State the given and needed quantities. Step 2: Write a temperature equation. = Step 3: Substitute in the known values and calculate the new temperature.

14 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 1: State the given and needed quantities. Step 2: Write a temperature equation. = Step 3: Substitute in the known values and calculate the new temperature. What is the normal body temperature, 37 C, in kelvins? A. 236 K B K C. 342 K D K Step 1: State the given and needed quantities. Step 2: Write a temperature equation. = or = Step 3: Substitute in the known values and calculate the new temperature. The Periodic Table of the Elements 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 T K = T C T K = Temperature Kelvin

15 Identify energy as potential or kinetic. Convert between units of energy. 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. makes objects move. makes things stop. is defined as the ability to do work. A defibrillator provides electrical energy to heart muscle to reestablish normal rhythm. 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.

16 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 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. 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 H 2 O molecules that are moving slowly increase their motion. eventually have enough energy to change the ice cube from a solid to a liquid.

17 How many calories are obtained from a pat of butter if it provides 150 J of energy when metabolized? A 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. The Periodic Table of the Elements 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 How many joules are obtained from an apple if it provides 90 cals of 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. Use the energy values to calculate the kilocalories (kcal) and kilojoules (kj) for food.

18 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! 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. 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. The caloric or energy value for 1 g of a food is given in kilojoules (kj) or kilocalories (kcal). The typical energy values are different for each food type. Remember: 1 Cal = 1 kcal

19 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? 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? The Periodic Table of the Elements 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

20 Use specific heat to calculate heat loss or gain. 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) Every substance has its own characteristic ability to absorb heat. Certain substances must absorb more heat than others to reach a certain temperature. The high specific heat of water keeps temperature more moderate in summer and winter. SH of water = 1.00 cal/g C =4.18J/g C

21 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. When we know the specific heat of a substance, we can calculate the heat lost or gained, by measuring its mass and temperature change. 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.

22 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? The Periodic Table of the Elements 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 What is the mass in grams of a metal that has a specific heat of J/g C, absorbs 320 J of energy and the temperature rises from 26.7 C to 115 C? Describe the changes of state between solids, liquids, and gases; calculate the energy involved.

23 Matter undergoes a change of state when it is converted from one state (solid, liquid, or gas) to another state. If the temperature of a liquid is lowered, (kinetic) energy is lost, slowing the particles down. The attractive forces of their neighbors pull the particles close together This is freezing Temperature = freezing point When heat is added to a solid, the particles move faster At a certain temperature, the particles have enough energy to break free of the attraction with their neighbors and move randomly. This is melting (solid liquid) Temperature = melting point Melting requires heat! Freezing releases heat! Every substance as its own meeting/freezing point. Water melts at 0 C, freezes at 0 C Gold melts at 1064 C, freezes at 1064 C

24 Heat of Fusion 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). Heat of Fusion for Water = 80 cal/g (or 334 J/g) To melt water, For a given amount of substance, heat released during freezing = heat needed during melting 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 water in a mud puddle disappears The higher the heat, the faster molecules gain enough energy to escape to gas.

25 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 Sublimation Deposition 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. 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. Sublimation and deposition are reversible processes. Dry ice sublimes at 78 C.

26 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. On a heating/cooling curve, diagonal lines indicate changes in temperature for a physical state, and horizontal lines (plateaus) indicate changes of state. How many kilojoules (kj) are released when 50.0 g of steam from a volcano condenses at 100 C? 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.

27 Use the cooling curve for water to answer each of the following: 1. Water condenses at a temperature of A. 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 is A. 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 1: State the given and needed quantities. 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 C is released. How many kilojoules are lost when the steam condenses, then freezes, at 0.0 C? Step 1: State the given and needed quantities. 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.

28