matter: properties and changes - norwell high school · 2014-10-10 · elements & compounds •...
TRANSCRIPT
Matter: Properties and Changes
Chapter 3.1: Properties of Matter
Substances
• Review:
• Matter is anything that has mass and takes up space.
• Matter with uniform and unchanging composition is pure substance.
• ie~ Table salt (NaCl)
• What about H2O? Pure water = yes; seawater / tap water = no.
Sates of Matter
• States of Matter
• All matter that exists can be classified into one of three forms:
• Each can be distinguished by the way it fills a container.
• Exception to rule: plasma (fourth state of matter)
• Found in lightning bolts and stars.
Chapter 3: Matter - Properties and
Changes
3.1 Properties of Matter
States of Matter
Solid -
Liquid -
Gas -
Vapor -
Physical Properties -
1
States of Matter
• Solid
• Definite shape and volume.
• Particles tightly packed.
• Expands slightly when heated.
States of Matter
• Liquid
• Flows and has constant volume.
• Particles not held in place and packed less closely.
• Able to move past one another.
• Takes shape of container.
• Expands when heated.
Chapter 3: Matter - Properties and
Changes
3.1 Properties of Matter
States of Matter
Solid -
Liquid -
Gas -
Vapor -
Physical Properties -
1
States of Matter
• Gas
• Flows to conform to shape of container & fills entire volume.
• Expands to fill containers.
• Particles are very far apart
• Easily compressible.
Chapter 3: Matter - Properties and
Changes
3.1 Properties of Matter
States of Matter
Solid -
Liquid -
Gas -
Vapor -
Physical Properties -
1
States of Matter
• Gases vs Vapor
• Do not mean the same thing!
• Gas is a substance that is naturally in the gaseous state at room temperature.
• Vapor refers to gaseous state of substance that is solid or liquid at room temperature
• Helium? Neon? Steam?
Physical Properties of Matter
• Characteristic that can be observed or measured without changing the composition.
• Also describe pure substances.
• Uniform and unchanging compositions = consistent and unchanging properties.
• Examples include: Density, color, odor, hardness, melting point, boiling point.
Chemical Properties -
3.2 Changes in Matter
Physical Change -
2
Physical Properties of Matter
• Two Types
• Extensive
• Dependent on the amount of substance present.
• Examples include: Length, mass, & volume.
Physical Properties of Matter
• Two Types
• Intensive
• Independent on the amount of substance present.
• Examples include: Density- always the same regardless of how much substance is present.
• Substances can be identified by intensive properties.
• ie~ scent
Chemical Properties of Matter
• The ability of a substance to combine with or change into one or more other substances.
• Composition of substance changes.
• Results from contact with other substances or addition of energy (thermal or electric).
• Example: Iron = Forms rust when in contact with oxygen in air
• Copper =
Chemical Properties -
3.2 Changes in Matter
Physical Change -
2
Chemical Properties of Matter
• Each substance has its own unique set of physical and chemical properties.
• Copper: Can be shaped into different forms (physical) or turns green when in contact with air (chemical)
Chemical Properties -
3.2 Changes in Matter
Physical Change -
2
Matter: Properties and Changes
Chapter 3.2: Changes in Matter
Changes in Matter
• Physical Change
• Changes in appearance but not composition.
• Examples include: 1) Cutting sheet of paper 2) Breaking glass object 3) Crumpling piece of aluminum foil
Changes in Matter
• Phase Change
• Transition of matter from one state to another.
• Depends on temperature and pressure of surroundings.
• As temperature and pressure change, substances change from one phase to another.
• Example is the water cycle:
• 1) Ice (solid) is heated to become liquid water. 2) Add more heat, liquid water boils and is converted to steam (gas).
• What type of changes are these? Physical (Different appearance but same composition)
Changes in Matter
• Phase Change
• Melting and Boiling Points
• The temperature and pressure at which a substance undergoes a phase change.
• Intensive physical properties that can be used to identify unknown substances.
Changes in Matter
• Chemical Change
• One or more substances changing into new substances.
• aka~ chemical reaction
• New substances formed have different compositions and properties.
Changes in Matter
• Chemical Reaction
• Starting substances = reactants.
• New substances formed = products.
Changes in Matter
• Chemical Reaction
• Evidence includes a change in properties.
• ie~ spoiled food: What are some changes in properties? Look, taste, digestability...
Chemical change -
Evidence of Chemical Change
Law of Conservation of Mass -
A 10.0 g sample of magnesium reacts with oxygen to form 16.6 g of Magnesium
oxide. How many grams of oxygen reacted?
3
Changes in Matter
• Law of Conservation of Mass
• Mass is neither created nor destroyed during a chemical reaction.
• It is conserved.
• mass of reactants = mass of products.
• Although chemical changes occur, total mass remains constant.
Changes in Matter
• Law of Conservation of Mass
• Mass is neither created nor destroyed during a chemical reaction.
Chemical change -
Evidence of Chemical Change
Law of Conservation of Mass -
A 10.0 g sample of magnesium reacts with oxygen to form 16.6 g of Magnesium
oxide. How many grams of oxygen reacted?
3
Matter: Properties and Changes
Chapter 3.3: Mixtures of Matter
Changes in Matter
• Most everyday matter occurs as mixtures.
• Combination of two or more pure substances.
• Each pure substance retains its individual chemical properties.
• Composition of mixtures is variable.
Changes in Matter
• Types of Mixtures
• Heterogeneous
• Mixture that does not blend smoothly.
• Composition is not uniform.
• Substances remain distinct.
• Examples include: salad dressing, orange juice, etc.
Changes in Matter
• Types of Mixtures
• Homogeneous
• Has constant composition throughout.
• Always has single phase.
• Referred to as solutions.
Changes in Matter
• Solutions
• Most familiar with liquid forms.
• Examples include: tea, lemonade, etc
• Solution systems can be solid, liquid, or gas.
• Solid-solid solutions of metals are known as alloys.
• Examples include: steel, bronze, 14-karat gold.
Changes in Matter
• Solutions
3.3 Mixtures of matter
Mixture -
Heterogeneous Mixture -
Homogeneous Mixture (solution) -
4
Separating Mixtures
• Important to be able to separate mixtures to understand nature of matter.
• Use physical processes to separate mixtures based on physical properties.
• ie~ magnet to separate metal from sand.
Separating Mixtures-
Filtration -
Distillation -
5
Separating Mixtures
• Filtration
• Separates heterogeneous mixtures composed of solids and liquids.
• Uses a porous barrier.
Separating Mixtures-
Filtration -
Distillation -
5
Separating Mixtures
• Distillation
• Used to separate most homogeneous mixtures.
• Based on differences in boiling points.
1) Mixture is heated until lower boiling
point boils to vapor.
2) Vapor is condensed into liquid and
collected.
Separating Mixtures
• Crystallization
• Results in the formation of pure solid particles of a substance.
• Solid particles come from solution containing dissolved substance.
• Solids are highly pure
• Example: rock candy
Crystallization -
Sublimation -
6
Crystallization -
Sublimation -
6
Separating Mixtures
• Sublimation
• Solid changes to vapor without going through liquid phase.
• Used to separate one solid that sublimates form one that does not.
Chromatography -
3.4 Elements and Compounds
Element -
Periodic Table -
Compounds -
7
Separating Mixtures
• Chromatography
• Separates components of a liquid mixture (mobile phase) based on ability of each to travel across another material (stationary phase).
• Components flow through stationary phase at different speeds.
Matter: Properties and Changes
Chapter 3.4: Elements and Compounds
Elements & Compounds
• Matter can take many different forms.
• All matter can be broken down into basic building blocks called elements.
• Element is a pure substance that cannot be separated into simpler substances by physical or chemical means.
• 92 natural elements
• Several others that have been developed
Elements & Compounds
• Elements have unique chemical names & symbols.
• Names consist of 1/2/3 letters.
• First ALWAYS capitalized; rest are lowercase.
• 92 natural elements not evenly distributed.
• H2: 75 % of mass of universe.
• O2, H2, C: 90% of human body
• Under normal conditions, elements can be found in each type of phase. (ie~ Cu, Hg, He)
Elements & Compounds
• Elements organized into a periodic table.
• Based on similarities and masses
• Rows = periods
• Columns = groups / families
• Elements in same group have similar chemical and physical properties.
Elements & Compounds
• Compounds made up of two or more different elements that are chemically combined.
• Most matter in the universe exists as compounds.
• 10 million known; ~ 100,000 developed each year.
• Chemical formulas of compounds
• Composed of chemical symbols and subscripts.
• Subscripts indicate number of elements in each compound.
• ie~ H2O, NaCl
Properties of Compounds vs. Elements
8
Elements & Compounds
• Compounds can be broken down into simpler elements by chemical means.
• Compounds generally more stable than individual elements.
• Requires energy (ie~ heat or electricity).
• Electrolysis is breakdown of H2O.
*** What do you notice about the amount
of H2 compared to the amount of O2?
Properties of Compounds vs. Elements
8
Properties of Compounds
• Properties of a compound are different from those of the individual elements.
• ie~ H2O
• How is H2O different than H2 & O2?
Properties of Compounds
• Properties of a compound are different from those of the individual elements.
Properties of Compounds vs. Elements
8
Law of Definite Proportions -
A 1.0 g sample of hydrogen reacts with 19.0 g of fluorine. What is
the % of hydrogen in the compound?
9
• Organization of Matter
• Pure substances & mixtures.
• Separation???
Properties of Compounds
Law of Definite Proportions
• Elements in compounds combine in definite proportions by mass.
• Law of Definite Proportions = Compound is composed of same elements in the same proportion by mass.
• Mass of the compound = sum of masses of elements that make up the compound.
Law of Definite Proportions -
A 1.0 g sample of hydrogen reacts with 19.0 g of fluorine. What is
the % of hydrogen in the compound?
9
Law of Definite Proportions
• Amounts of elements in a compound can be expressed as percent by mass.
• Ratio of the mass of each element to the total mass of the compound.
Law of Definite Proportions -
A 1.0 g sample of hydrogen reacts with 19.0 g of fluorine. What is
the % of hydrogen in the compound?
9
Law of Definite Proportions
• Amounts of elements in a compound can be expressed as percent by mass.
• Ratio of the mass of each element to the total mass of the compound.
• Percent by mass the same regardless of amount of sucrose; each has the same mass proportion
Law of Multiple Proportions - When different compounds are
formed by a combination of the same elements, different mass of
one element combine with the same relative mass of the other
element in a ratio of small whole numbers
10
Law of Multiple Proportions
• Use when comparing different compounds composed of the same elements.
• Law of Multiple Proportions = Different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers.
Law of Multiple Proportions
Law of Multiple Proportions - When different compounds are
formed by a combination of the same elements, different mass of
one element combine with the same relative mass of the other
element in a ratio of small whole numbers
10
mass ratio of Compound I mass ratio of Compound II = 1.793 g Cu / g Cl
0.8964 g Cu / g Cl = 2.000
• Mass ratio of copper to chlorine in Compound 1 is exactly two times the mass ratio of copper to chlorine in Compound II.
• 2:1