c hapter 1: m atter and c hange chemistry 1-2 mr. chumbley
TRANSCRIPT
CHAPTER 1: MATTER AND CHANGEChemistry 1-2
Mr. Chumbley
SECTION 1: CHEMISTRY IS A PHYSICAL SCIENCE
WHAT IS CHEMISTRY?
For most of human history, the natural sciences were divided into two broad categories: Biological Sciences Physical Sciences
However, those divisions began to break down as knowledge increased
Chemistry is the study of the composition, structure, and properties of matter, the processes that matter undergoes, and the energy changes that accompany these processes
BRANCHES OF CHEMISTRY
As the understanding of matter and its processes increased, different branches of chemistry arose to better describe specific types of chemicals and processes
A chemical is any substance that has a definite composition
Organic Chemistry Inorganic Chemistry
Physical Chemistry Analytical Chemistry
Biochemistry Theoretical Chemistry
CHEMISTRY APPLICATIONS
Basic chemical research is conducted for the purpose of expanding knowledge
Applied chemical research is conducted for the purpose of solving a specific problem
Technological development involves the production and use of products to improve the quality of life
HOMEWORK
Read: Chapter 1, Sections 2: Matter and Its Properties Stop once you get to “Main Idea: Matter can be a
pure substance or a mixture.”
SECTION 2: MATTER AND ITS PROPERTIES
WHAT IS MATTER? It is much easier to identify that things are made up
of matter than it is to define matter
By looking at the same properties for all matter there are two universal commonalities: Things made of matter take up space (have volume) Things made of matter have mass
Mass is a measure of the amount of matter
Using these universal characteristics we can define matter
Matter is anything that has mass and takes up space
ATOMS ARE THE BUILDING BLOCKS OF MATTER
While matter exists in many different forms, the most fundamental form is the atom
An atom is the smallest unit of an element that maintains the chemical identity of that element
An element is a pure substance that cannot be broken down into simpler, stable substances and is made of one type of atom
ATOMS ARE THE BUILDING BLOCKS OF MATTER
When atoms of different elements chemically combine, molecules of a compound are formed
A compound is a substance that can be broken down into simple stable substances, but is made from the atoms of two or more elements that are chemically bonded
The smallest unit of a compound is a molecule
ALL SUBSTANCES HAVE CHARACTERISTIC PROPERTIES The specific characteristics of a substance, either element or
compound, are considered its properties
Properties can be used to identify individual substances, or an entire group of substances
Properties can be one of two types
Extensive properties depend on the amount of matter present mass volume total energy
Intensive properties do not depend on the amount of matter present melting point boiling point density conductivity
PHYSICAL PROPERTIES
Properties of substances are often used as identifying characteristics
Physical properties are characteristics that can be observed or measured without changing the identity of the substance
Examples:mass color shape
density volume texture
boiling point melting point conductivity
PHYSICAL CHANGES
The physical properties of a substance are can change, even if the substance does not
A physical change is a change in a substance that does not involve a change in the identity of the substance
Examples:cutting grinding polishing
boiling melting dissolving
STATES OF MATTER
Matter exists in states of matter that are physical properties
When a substance undergoes a change of state, it is a physical change from one state to another
While the substance has some new and different physical properties, the chemical identity has not changed
STATES OF MATTER
State of Matter
Definite Shape
Definite Volume
Solid Yes Yes
Liquid No Yes
Gas No No
As a substance changes from solid to liquid to gas, the atoms or molecules become less organized and have increasing ability to move away from each other
A fourth state of matter, plasma, is a high-temperature physical state of matter in which atoms lose most of their electrons
CHEMICAL PROPERTIES
In any situation where a substance could change its identity, chemical properties can be observed
Chemical properties relate to a substances ability to undergo changes that transform it into a different substance
Examples:reactivity chemical
stability flammability
toxicity combustibility radioactivity
CHEMICAL CHANGES
A chemical change (or chemical reaction) is a change in which one or more substances are converted into different substances
The reactants are the substances that react in a chemical change
The products are the substances that are formed by the chemical change
SIGNS OF A CHEMICAL CHANGE
Production of an odor
Change in temperature
Change in color
Formation of bubbles
Formation of a solid
Emission of light
ENERGY AND CHANGES IN MATTER
In both physical and chemical changes, energy is involved
Many different types of energy can be involved
The law of conservation of energy says that energy can be absorbed or released, but it is never created nor destroyed
HOMEWORK
Read: Chapter 1, Sections 2: Matter and Its Properties Start at “Main Idea: Matter can be a pure
substance or a mixture.” Finish at the end of Section 2 Answer #1-5 of the Formative Assessment on p.
14
MATTER CAN BE A PURE SUBSTANCE OR A MIXTURE
The variety of forms in which matter can exist is enormous
Two major classifications of matter are whether or not it is a pure substance or a mixture
Regardless of whether a sample is a pure substance or a mixture, it can be described and classified in terms of its properties
PURE SUBSTANCES
A pure substance is any form of matter that has a fixed, or definite, composition
Pure substances have two defining characteristics:
Every sample of a given pure substance has exactly the same characteristic properties.
Every sample of a pure substance has exactly the same composition.
MIXTURES
A mixture is a blend of two or more kinds of matter each of which retains its own identity and properties
Another way of describing a mixture is that the matter combines physically, but not chemically
Since mixtures do not have a defined composition, the amount of different substances within a sample of a mixture must be specified
MIXTURES
Mixtures can be described by the uniformity of their compostion
Homogeneous mixtures (or solutions) are mixtures that are uniform in composition
Heterogeneous mixtures are mixtures that are not uniform in composition
MIXTURES
One of the most important characteristics of a mixture is that it can be physically separated
Examples of physical separation: Filtration Vaporization Settling Centrifuge separation Chromatography
LABORATORY CHEMICALS AND PURITY
Typically, we treat chemicals used in the laboratory is if they were pure
Chemicals do have impurity, and depending on the standards and grade desired or used
The level of purity is important to know since the level of impurities can affect results