IntroductionMatter

and Change

Unit 1

What is Chemistry?

Chemistry is the study of matter and its interactions.

We will study the following properties of matter:• composition• properties• interactions• changes

How will matter be studied?

Using the scientific method.

What is the Scientific Method?

Logical approach to exploring a problem or question that has been raised through observation.

Designed to produce a solution or answer that can be tested, retested, and supported by experimentation.

1.State the problem.2.Gather information about the problem.3.Form a hypothesis.4.Test hypothesis.

- variables- controlled experiments

5.Gather and organize data and observations.6.Interpret data.7.Form a conclusion.8.Replication.

What are the steps of the Scientific Method?

What happens to a hypothesis?

Model: An explanation of how phenomena occur and how data or events are related.

Theory: A broad generalization that explains a body of facts or phenomena.

Scientific Law: Statement or mathematical expression about behavior of the natural world.

Use the following terms to organize a Concept Map for matter.

• Can it be separated?• Is composition uniform?• Can it be decomposed by

ordinary chemical means?• Elements• Compounds• Mixtures• Pure Substance• Heterogeneous mixture• Homogeneous mixture

• Air• Stainless steel• Blood• Wood • Water• Sodium chloride• Gold• Oxygen

Matter – anything that has mass and volume.

Matter

How is matter classified? Matter is broken down into two major categories

- Pure Substance- Mixture

- Have unique properties- Cannot be separated by physical means- There are two categories of pure substances:

Elements and Compounds

Pure Substance

Elements - simplest pure substances - contain only one kind of atom - cannot be broken down by physical or chemical means - unique physical and chemical properties

Compounds - substance composed of 2 or more elements that are chemically combined - have unique chemical and physical properties - can be broken down chemically (not physically)

- properties of elements that compounds are broken down into do not resemble properties of original

compound - always break down to the same proportion by mass

Mixtures- Collection of 2 or more pure substances physically mixed together. (No chemical formula)- Properties vary depending on what is in the mixture- Composition can vary (no definite proportion)- There are 2 types of mixtures:

HeterogeneousHomogeneous

Homogeneous Mixture - Substances are distributed evenly throughout the mixture - All regions are identical in their composition and propertiesHeterogeneous Mixture - Substances are not evenly distributed throughout the mixture - Some regions have different properties than others

Classification of Matter

Matter is described by its properties

Extensive Properties- Depend on how much of a substance there is- Not useful in identifying the substance.

Intensive Properties- Properties that do not depend on size.- Can be useful in identifying the substance.

Comparing Extensive and Intensive Properties

Physical Properties- Characteristics that can be observed without changing the substance.- Melting point and boiling point are

examplesPhysical Change- Change in a substance that does not involve a change in the identity of the substance.- Phase changes are examples:

solid to liquid - meltingliquid to solid - freezingliquid to gas - vaporizationgas to liquid - condensationsolid to gas - sublimationgas to solid - deposition

Phase Changes are also called changes in state.

There are 4 states of matter: Solid

Liquid

Gas

Plasma

Phase Diagrams

A phase diagram is a graph of pressure versus temperature that shows the conditions under which the phases of a substance exist.

The triple point of a substance indicates the temperature and pressure conditions at which the solid, liquid, and vapor of the substance can coexist at equilibrium.

The critical point of a substance indicates the critical temperature and critical pressure.

Phase Diagram

Phase Diagram

Phase Diagram for CO2

Changes of State - Summary

Water in Three States

Heating Curve for Water

Heat of Fusion: The amount of energy as heat required to melt a solid at the solid’s melting point

Heat of Vaporization: The amount of energy as heat that is needed to vaporize a liquid at the liquid’s boiling point at constant pressure

Chemical Properties- characteristics that describe how a substance interacts (or fails to interact) with other substances.

Chemical Change- also called a chemical reaction- change that results in production of 1 or more substances that differ in chemical properties and composition from the original substance

Chemical Reaction

Evidence of a Chemical Change

Comparison of Physical and Chemical Properties

Comparing Physical and Chemical Properties

Comparing Chemical and Physical Changes

Periodic Table of the Elements

Review Questions1. Matter that has a definite shape and a definite volume is?2. Why is air considered a mixture and not a compound?3. How do compounds differ from mixtures?4. Is each of the following a chemical or physical property?

A. Its mass is 124.3 g.B. It is a shiny solid at room temperature.C. It is easily etched by nitric acid.D. It melts when heated to 670°C.E. It is 31.7 centimeters long.F. It is a good heat conductor.G. It burns in air.H. It is a good conductor of electrical energy

5. Describe the difference between a chemical change and a physical change. Give one example of each kind of

change.