Chapter 1 Chemistry: The Study of Matter

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Transcript Chapter 1 Chemistry: The Study of Matter

Matter: Properties and Changes Chapter 3

Chemistry is the Study of Matter What is Matter?



Matter

is anything that takes up space and has mass.



Mass

is the amount of matter in an object.



Volume

is a measure of space taken up.

Matter is Diverse

 All matter falls into two categories. – Pure Substance: element or compound – Or Mixtures (of substances) – We must describe and classify matter in order to understand it.

Pure Substance

 A

substance

is matter that has a uniform and unchanging composition  Example: pure water  No matter where it is found, a sample of water will have the same composition as any other sample of water  Other Examples: Table Salt,

Types of Matter



Any element or any compound is a Pure Substance

– Elements: H, C, Ne, Li – Compounds: sodium chloride, carbon dioxide, LiBr, C 6 H 12 O 6 

Mixture-

more than one kind of matter – Combinations of elements and compounds

6 How do we describe matter?

PROPERTIES

Properties

Characteristics and Behaviors 

Physical Properties

- can be observed and measured without changing the chemical composition of the substance.

 Describes how a substance looks, feels, smells, tastes, etc.  Examples: color, density, hardness, texture, crystal size

Physical Properties

 Intensive Physical Properties – Do not change when the sample size changes – Good for identification of matter – Density, odor, boiling pt, freezing pt  Extensive Physical Properties – Change as the sample size changes – Mass, volume, length, weight

States of Matter: Physical Properties



Solid

- mater that can not flow and has definite volume.



Liquid

- definite volume but takes the shape of its container (flows).



Gas

- a substance without definite volume or shape and can flow.



Vapor

- a substance that is currently a gas but normally is a liquid or solid at room temperature.

Freeze

Melt

Condense

Evaporate 12 Solid Liquid Gas

Chemical Properties

 A property that can only be observed by changing the type of substance.  Describes the ability of a substance to combine with or change into one or more other substances.  Describe how a substance behaves  Describes how a substance interacts with other matter

Chemical Properties

 Flammability  Reactivity  Explosiveness,  Ability to rust  Ability to burn or not burn

Non-reactivity is also chemical

 The inability of a substance to combine with another substance is also a chemical property.  the inability to combine with most other substances is a chemical property of gold.

16 Identify as chemical and physical property 2.

Silver tarnishes when it comes in contact with hydrogen sulfide in the air.

A sheet of copper can be pounded into a bowl.

Barium melts at 725 °C.

Helium does not react with any other element.

A bar of lead is more easily bent than is a bar of aluminum of the same size.

Potassium metal is kept submerged in oil to prevent contact with oxygen or water.

Diamond dust can be used to cut or grind most other materials.

Rocks containing carbonates can be identified because they fizz when hydrochloric acid is applied.

Mini Lab: Zinc and HCl

Materials: Test tube Small piece of Zinc 10 mL of HCl 1.

Record the physical properties of the zinc metal. Record the physical properties of the HCl.

18  With the test tube in the test tube rack, drop the zinc into the HCl. – Observe. Be sure to touch the bottom of the tube. – Light a wooden splint and do a flaming splint test. Record your results. What gas does this result confirm?

Post Lab

 1. What is the gas a sign of?  2. The equation for this reaction is Zn + HCl  ??? What are the products? 3. What is the identity of the gas produced? Give two reasons to support your prediction. 4. Name a chemical property of Zinc and a chemical property for HCl.

More analysis

Give some reasons you know that a chemical reaction happened when you added zinc to HCl What happens in the flaming splint test? Write the equation for the flaming splint test? Name something on a bigger scale that this flaming splint test is like.

Two Types of Changes in Matter

 Physical Changes or Chemical Changes

Physical Changes

 A change that changes appearances, without changing the composition.

 Changes that do not alter the composition of matter – Verbs used to indicate physical changes » Boil » Dissolve » Tear » Grind Melt Break Condense Split Freeze Shatter Crumple Crush

23 A physical change

Grinding Coffee

24 Physical Change

Boiling Water

Chemical Change

 Occurs when one or more substances change into new substances.  also known as a

chemical reaction .

 The appearance of new substances is the sign that a chemical reaction has occurred

Chemical Changes

 Change where a new form of matter is formed.

 Verbs used to indicate a chemical change – Burn – Decay – Rot Oxidize Ferment Rust – Reacts with – Decomposes Corrode Tarnish

30 Chemical change

Frying an Egg

31 A chemical change

A rotting pumpkin

Combustion of Iron

 A Chemical Reaction  http://www.youtube.com/watch?v=awdbiiTiWK k&feature=plcp

35 Leaves Changing Colors in the Fall Fireworks

Chemical Reactions

 When one or more substances are changed into new substances.

 Reactants materials you start with  Products What you make  NEW PROPERTIES  Not easily reversed

Indicators of Chemical Reactions

 Production of a gas (smell or bubbles)  Production of a solid (precipitate)  Color Changes  Changes in Energy (temperature)

39 1.

Classify as Physical or Chemical

Moisture in the air forms beads of water on a cold windowpane.

An electric current changes water into hydrogen and oxygen.

Yeast cells in bread dough make carbon dioxide and ethanol from sugar.

Olive oil, vinegar, salt, and pepper are shaken together to make salad dressing.

Molten bronze is poured into a mold and solidifies to form a figurine.

A reactant decomposes to form two products

Lab

 Evidence of a Chemical Reaction

Law of Conservation of Mass

 Mass Reactants = Mass Products  One of the greatest achievements of 18 th century science  Antoine Lavoisier was one of the first to use an analytical balance to show this.

Conservation of Mass

 Mass can not be created or destroyed in ordinary (not nuclear) changes.

 All the mass can be accounted for.

43  Dalton's atomic theory addressed this when he said that

chemical reactions involve the rearrangement of atoms and atoms are neither created nor destroyed in chemical reactions

 This law is why chemical equations have to be Balanced.

Example Problem

 When 10 grams of calcium are burned in oxygen, 14 grams of calcium oxide are formed. How many grams of oxygen react?

45  Conservation of mass says that the sum of the masses of the reactants must be the same as the sum of the masses of the products  Reactant Mass = Product Mass  Calcium + oxygen  calcium oxide  10 g Ca + ? gO 2 = 14 g CaO 4 gO 2

46 

Example Problem

A thin strip of iron with a mass of 15.72 g is placed into a solution containing 21.12 g of copper (II) sulfate and copper begins to form. After a while, the reaction stops because all of the copper(II) sulfate has reacted. The iron strip is found to have a mass of 8.33 g. The mass of copper formed is found to be 8.41 g. What mass of iron(II) sulfate has been formed in the reaction?

Solution

Apply the Law of Conservation of Mass – Mass reactant 1 + Mass reactant 2 = Mass product 1 + Mass product 2 Rewrite the equation with the names of the reactants and products.

– Mass iron + Mass copper sulfate = Mass copper + Mass iron sulfate To find the mass of iron sulfate, rearrange the equation.

– Mass iron sulfate = Mass iron + Mass copper sulfate - Mass copper Then, determine the mass of iron that reacted.

– Mass iron – Mass iron = original mass of iron - mass of iron remaining = 15.72 g - 8.33 g = 7.39 g Finally, substitute the masses into the equation and solve.

– Mass iron sulfate = 7.39 g + 21.12 g - 8.41 g = 20.10 g iron sulfate To check your work, make sure the sum of the masses of the reactants is equal to the sum of the masses of the products.

48  We also have to remember to put the units by each number; this helps us keep track of what's going on and also expresses to the reader that we are dealing with mass and not some other property.

Practice Problems

 A sealed glass tube contains 2.25 g of copper and 3.32 g of sulfur. The mass of the tube and its contents is 18.48 g. Upon heating, a reaction forms copper(II) sulfide (CuS). All of the copper reacts, but only 1.14 g of sulfur reacts. Predict what the mass of the tube and its contents will be after the reaction is completed. Explain your reasoning.

51  When heated, calcium hydroxide and ammonium chloride react to produce ammonia gas, water vapor, and solid calcium chloride. Suppose 5.00 g of calcium hydroxide and 10.00 g of ammonium chloride are mixed in a test tube and heated until no more ammonia is given off. The remaining material in the test tube has a mass of 10.27 g. What total mass of ammonia and water vapor was produced in the reaction?

53  When a solution of barium nitrate and a solution of copper(II) sulfate are mixed, a chemical reaction produces solid barium sulfate, which sinks to the bottom, and a solution of copper(II) nitrate. Suppose some barium nitrate is dissolved in 120.00 g of water and 8.15 g of copper(II) sulfate is dissolved in 75.00 g of water. The solutions are poured together, and a white solid forms. After the solid is filtered off, it is found to have a mass of 10.76 g. The mass of the solution that passed through the filter is 204.44 g. What mass of barium nitrate was used in the reaction?

55  A reaction between sodium hydroxide and hydrogen chloride gas produces sodium chloride and water. A reaction of 22.85 g of sodium hydroxide with 20.82 g of hydrogen chloride gives off 10.29 g of water. What mass of sodium chloride is formed in the reaction?

Solve 5-9 and 50-55

Mixtures

 a combination of two or more pure substances  each substance retains (keeps) its individual properties  Not uniform and unchanging in composition  Composition varies

Mixtures

 Concrete, most rocks, most metal objects, all food, and the air you breathe  All mixtures that are often composed of many different substances.  The composition of a mixture is variable .  For example, the composition of salt water can be varied by changing the amount of salt or water in the mixture.

Two types of mixtures



Heterogeneous Mixture

 Homogenous Mixtures

Heterogeneous mixture

– mixture is not uniform throughout – Not blended smoothly – Not the same from spot to spot » Chocolate chip cookie » gravel » Soil » Muddy water » Smoky air

Homogeneous mixture

– same composition throughout – Uniform – Blended smoothly – Kool-aid – air – Every part retains its properties – Also called

Solutions

 Homogeneous mixture  Mixed molecule by molecule  Can occur between any state of matter.

– Solid in liquid- Kool-aid – Liquid in liquid- antifreeze – Gas in gas- air – Solid in solid - brass – Liquid in gas- water vapor – Gas in liquid-pop

63 1.

Classify as Heterogeneous or Homogeneous

70% isopropyl rubbing alcohol a pile of rusty iron filings concrete saltwater gasoline bread

Solutions

 Like all mixtures, they keep the properties of the components.

 Can be separated by physical means using

differences in properties

of the components  Not easily separated-

can

be separated.

What are physical means?

 Picking it apart  Using a magnet  Filtration  Distillation  Crystallization  Chromatography  http://amrita.olabs.co.in/?sub=73&brch= 2&sim=96&cnt=207

Separation of a Mixture

Salt, Sand, and Iron Filings (150 grams) Use a magnet to separate iron Iron Filings (60 grams) Sand ( 50 grams) Salt Sand and Salt Add Water Filter the suspended solid Salt and Water Evaporate the water (40 grams) Water

Lab: Chromatography

 Mixtures Separation WS  Solve 56-64

Comparison of a Compound to a Mixture

Composition Creation Separation/breakdown

Compound

One kind of particle Molecules/Formula Units Chemical Means Chemical

Mixture

More than one type of particle Physical Means Physical http://amrita.olabs.co.in/?sub=7 3&brch=2&sim=70&cnt=205

69 Element

Which is it?

70 Of two elements

Mixture

Compound

Element, Compound, or Mixture

sucrose (table sugar) the helium in a balloon baking soda a diamond aluminum foil the substances listed on the periodic table calcium chloride pellets used to melt ice

Relationships

75  Composed of one or more of about 100 elements

All Matter

Substances Elements

- simplest kind of matter  Cannot be broken down into simpler substances  All one kind of atom.

Chemical Symbols

 There are 113 elements  Each has a 1 or two letter symbol  First letter always capitalized second never  Don’t need to memorize all  Some from Latin or other languages  We will memorize 52 common elements and symbols

Compounds



Compounds

are substances that can be broken down by chemical methods  When they are broken down, the pieces have completely different properties than the compound.

 Made of two or more atoms Al + Br 2 reaction http://www.youtube.com/watch?v=5aaQGsVFaoI

Formulas of Compounds

 combinations of symbols to represent combinations of atoms   These combinations of symbols are called

formulas.

Much like we can make words by combining letters, we can make formulas by combining symbols.  You can also write down the formula of the compound if you are given the information about how many atoms are in it.

H

O

 H 2 O simply means that there are two atoms of hydrogen bonded to one oxygen atom, a ratio of two hydrogen atoms for every one oxygen atom.

– The subscript follows the symbol of the element to which it refers.

sodium chloride

 NaCl  no space between them  represents sodium chloride--a combination of sodium and chlorine in a 1:1 ratio by atoms.

formula for molecular hydrogen

 written as H 2 .  The 2 subscript immediately following the H means that there are two hydrogen atoms combined with one another.  H 2 i s a molecule.

molecular oxygen

 The formula for is O 2 .  the subscript 2 shows that there are 2 oxygen atoms bonded together.  the formulas represent the molecules of the element  symbols represent the atoms of these element

glucose

 C 6 H 12 O 6  represents 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms

85 

Fe(NO

)

3 In the formula Fe(NO 3 ) 3 parentheses you have to contend with  The 3 at the end of the formula--the one that is outside the parentheses--means that we have 3 of everything inside the parentheses.  So there are 3 NO 3 's which would be a total of 3 nitrogen atoms and nine oxygen atoms, along with the 1 iron atom.   The last 3 doesn't apply to the iron. It only applies to what's inside the parentheses. The 3 inside the parentheses applies only to the oxygen.

Practice Interpreting Formulas

 How many calcium atoms, how many phosphorus atoms, and how many oxygen atoms are represented by the formula Ca 2 (PO 4 ) 3 ?

Write the Formula from the Info

 a particular compound has 1 sulfur atom for every 3 oxygen atoms  Write the formula  A particular molecule is made of 2 nitrogen atoms and 5 oxygen atoms.

 Write the formula.

Important Characteristics of Compounds

 Elements combine in definite proportion – Same percent by mass every time – EX: Water is always 11.2% H and 88.8 % O 

Law of Definite Proportion:

regardless of sample size, a compound is always composed of the same elements in the same percent by mass  Also called Law of Definite Composition

Example

 100.00 g of H 2 O always contains 11.2 g of hydrogen and 88.8 g of oxygen  11.2 % hydrogen  88.8 % oxygen  no matter where the water came from  Compounds can often be identified from their percentage composition

Sucrose Analysis

Percent Composition of a Compound



Percent Composition

- The percent composition of an element in a compound is the percent of the total mass of the compound that is due to that component.



To calculate

the percent composition of a component in a compound:

93 1.

Find the molar mass of the compound by adding up the masses of each atom in the compound 2.

Divide the mass of the element in the compound by the total molar mass of the compound and multiply by 100.

Example Percent Composition

 Calculate the percent composition of carbon in the following: CO 2  Molar mass of compound  Percent Composition of carbon

Example Percent Composition

 Calculate the percent composition of carbon in C 6 H 12 O 6  Molar mass of compound  Percent composition of carbon

Example

 Suppose you break a compound down into its elements and find that 25.00 g of the compound is composed of 6.77 g of tin and 18.23 g of bromine. Calculate the percent by mass of tin in the compound.

Example

 Aluminum oxide has a composition of 52.9% aluminum and 47.1% oxygen by mass. If 16.4 g of aluminum reacts with oxygen to form aluminum oxide, what mass of oxygen reacts?

Practice

 A 2.89-g sample of sulfur reacts with 5.72 g of copper to form a black compound. What is the percentage composition of the compound?



Practice Problem

 134.50-g sample of aspirin is made up of 6.03 g of hydrogen, 80.70 g of carbon, and 47.77 g of oxygen. What is the percent by mass of each element in aspirin?

100

Law of Multiple Proportion

– Two compounds formed from the same elements, different masses of the same element combine with the same relative mass of the other element in a small whole number ratio. – Examples: water and hydrogen peroxide – copper (I) chloride and copper (II) chloride

101

Equations for Multiple Proportion

 Mass Ratio for Cmpd I = 𝑀𝑎𝑠𝑠 𝐸𝑙𝑒𝑚𝑒𝑛𝑡 𝐴 𝑀𝑎𝑠𝑠 𝐸𝑙𝑒𝑚𝑒𝑛𝑡 𝐵  Mass Ratio for Cmpd II = 𝑀𝑎𝑠𝑠 𝐸𝑙𝑒𝑚𝑒𝑛𝑡 𝐴 𝑀𝑎𝑠𝑠 𝐸𝑙𝑒𝑚𝑒𝑛𝑡 𝐵 𝑀𝑎𝑠𝑠 𝑅𝑎𝑡𝑖𝑜 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐼  = 𝑎 𝑠𝑚𝑎𝑙𝑙 𝑤ℎ𝑜𝑙𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑀𝑎𝑠𝑠 𝑟𝑎𝑡𝑖𝑜 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝐼𝐼

102

Law of Multiple Proportion

103

Example of

Law of Multiple Proportions

 Carbon combines with oxygen to form CO and CO 2 .

CO Mass of Carbon(g) 12.01

Mass of Oxygen(g) Ratio of O in CO 2 to O in CO 16.00

CO 2 12.01

32.00

2:1

104

Practice Problem 1

In the carbon compounds ethane (C 2 H 6 ) and ethene (C 2 H 4 ), what is the lowest whole number ratio of H atoms that react with the same number of C atoms?

105

Practice Problem 2

Carbon reacts with oxygen to form two compounds as shown: Compound A: 2.41 g C, 3.22 g O. Compound B: 6.71 g C, 17.9 g O. Find the lowest whole number ratio of C that react with an equal mass of O.

106

Practice Problem 3

Lead forms two compounds with oxygen as shown: Compound A: 2.98 g Pb, 0.461 g O.

Compound B: 9.89 g Pb, 0.763 g O.

For a given mass of oxygen, what is the lowest whole number mass ratio of lead in the two compounds?

107