1. Basic Concepts of Chemistry
Chapter 1

2. Overview Chemistry and Its Methods Classifying Matter
Elements and Atoms
Compounds and Molecules
Physical Properties
Physical and Chemical Changes

3. Chapter Goals
Understand the differences between hypotheses, laws and theories.
Apply the KMT to the properties of matter.
Classify matter.
Recognize elements, atoms, compounds and molecules.
Identify physical and chemical properties and changes.

4. 1.1 Chemistry and Its Methods
Chemistry is about change.
More specifically chemistry is about changing from one pure substance into another.

5. 1.1 Chemistry and Its Methods
A hypothesis is a tentative explanation or prediction based on experimental observations.
After formulating a hypothesis, chemists perform experiments designed to give results that confirm or invalidate their hypothesis.
This usually required qualitative and quantitative information to be collected and analyzed.

6. 1.1 Chemistry and Its Methods
Quantitative information is numerical data, such as temperature or mass of a solid used.
Qualitative information consists of non-numerical observations like color or texture of a sample.

7. 1.1 Chemistry and Its Methods
After a hypothesis has been formed and multiple experiments have been carried out to ensure reproducibility, chemists look for patterns of results that they then can summarize into a conclusion or to form a general rule.
Finally, after numerous experiments by many scientists over an extended period of time, the original hypothesis might become a law.

8. 1.1 Chemistry and Its Methods
A law is a concise verbal or mathematical statement of a behavior or a relation that is consistently observed in nature without contradiction.
After enough reproducible experiments have been conducted, and experimental results have been generalized as a law…
It may be possible to conceive a theory to explain the observations.

9. 1.1 Chemistry and Its Methods
A theory is a well-tested, unifying principle that explains a body of facts and the laws based on them.
Even though theories are the cornerstone of our understanding of the natural world at a given time…
Theories are inventions of the human mind and can and do change as new facts are uncovered.

10. 1.1 Chemistry and Its Methods
The goals of science are to predict, control and to gain understanding about our surroundings.
We do experiments and seek generalities because we want to be able to predict what may occur under a given set of circumstances.
We also want to know how we might control the outcome of a chemical reaction or process.

11. 1.2 Classifying Matter
An easily observed property of matter is its state—solid, liquid or gas.
The kinetic molecular theory of matter helps us interpret the properties of solids, liquids and gases.
According to this theory, all matter consists of extremely tiny particles (atoms, molecules or ions) which are in constant motion.

12. 1.2 Classifying Matter
In solids, the particles are packed tightly together in regular patterns and they vibrate back and forth about their average positions and only contact the other particles immediately next to themselves.
In liquids, the particles are arranged randomly and the particles are not confined to specific locations and can move past one another.

13. 1.2 Classifying Matter
The particles of a gas are spaced far apart and they are moving very rapidly because they are not at all constrained by their neighbors and they fill up any container they are placed in.
The higher the temperature of the material the faster the particles move.
The energy the particles have works to overcome the forces of attraction between particles.

14. 1.2 Classifying Matter
Macroscopic observations take place with the human senses.
Microscopic and submicroscopic observations or interpretations take place at the molecular level.
Chemists are interested in the structure of matter at the particulate level.
Chemists imagine what molecules must look like and how they fit together and then they create models to represent atoms and molecules…
And then use these models to think about chemistry and to explain the observations they have made about the macroscopic world.

15. 1.2 Classifying Matter
So, chemists carry out experiments at the macroscopic level, but they think about chemistry at the particulate level.
Then they write down their observations as symbols and drawings that represent the elements and compounds involved.

16. 1.2 Classifying Matter H2O (liquid)  H2O (gas) Macroscopic
Particulate
H2O (liquid)  H2O (gas)
Symbolic

17. 1.2 Classifying Matter
Matter, which may be solid-liquid-gas, is anything that occupies space and has mass.
Matter is split into heterogeneous (non-uniform composition) and homogeneous (uniform composition throughout) matter.
Heterogeneous matter can be physically separated into homogeneous matter.

18. 1.2 Classifying Matter
Homogeneous matter is made up of pure substance with a fixed composition that cannot be purified further and
solutions which are homogeneous mixtures with uniform compositions that may vary widely.
Homogeneous solutions can be physically separated into pure substances.

19. 1.2 Classifying Matter
Pure substances can be divided up into compounds and elements.
Compounds are made of elements that are chemically combined in fixed ratios.
Elements cannot be subdivided further by chemical or physical means.
Compounds can chemically be broken down into elements.
Elements can be chemically combined to form compounds.

20. 1.3 Elements and Atoms
Currently 117 elements are known and only 90 are naturally found in nature…the others are synthetically made by scientists in lab situations.
The periodic table lists all of these elements.
An atom is the smallest particle of an element that retains the characteristic chemical properties of that element.

21. Quick Quiz Name these elements…Na, Cl and Cr.
What are the symbols for…zinc, nickel and potassium?

22. 1.4 Compounds and Molecules
A pure substance made up of 2 or more elements that are held together by chemical bonds is referred to as a chemical compound.
When elements combine to form compounds the individual characteristics of those elements change.
Think of NaCl vs. Na and Cl.

23. 1.4 Compounds and Molecules
A mixture of pure elements and a chemical compound are very different.
Pure iron shavings and pure powdered sulfur can be mixed together and we still see each element.
We can mix iron and sulfur in varying proportions.

24. 1.4 Compounds and Molecules
But when iron and sulfur chemically combine into iron pyrite, we do not see the iron or the sulfur anymore.
The iron and sulfur are combined in a fixed ratio…FeS2.

25. 1.4 Compounds and Molecules
Some compounds are composed of ions, which are electrically charged atoms or group of atoms…NaCl.
Other compounds consist of molecules like H2O.
The composition of any compound is represented by its chemical formula…like NaCl or H2O.

26. 1.5 Physical Properties
Properties that can be observed and measured without changing the composition of a substance are called physical properties.
These properties allow us to classify and identify substances.
Some PP’s are color, state, MP, BP, density, solubility, conductivity, malleability, ductility, and viscosity.

27. 1.5 Physical Properties
Density is a ratio of the mass of a substance compared to its volume and typically measured as g/mL or g/cm3 or g/L.
Density = mass / volume or D = m/V
The density of a substance like water changes with temperature…this is why glassware is labeled the way it is.

28. 1.5 Physical Properties
Extensive properties depend on the amount of a substance present.
Intensive properties do not depend on the amount of a substance present.
The heat evolved when burning gasoline is extensive while ice melting at 0ºC is intensive.

29. 1.6 Physical & Chemical Changes
A physical change is a change in the physical appearance of a substance but it does not change the substance…melting ice.
A chemical change is when one or more substances (reactants) are transformed into one or more different substances (products).
The representation of a chemical change is a chemical equation.
A chemical property indicated whether and sometimes how easily a material undergoes a chemical change with another material.

30. Remembering the Chapter Goals…
Understand the differences between hypotheses, laws and theories.
Apply the KMT to the properties of matter.
Classify matter.
Recognize elements, atoms, compounds and molecules.
Identify physical and chemical properties and changes.

31. AP Chem Mini Quiz
What is the difference between a qualitative observation and a quantitative observation? Give 3 example of each.
What is an intensive property?
What is an extensive property?
Fill in the Venn Diagram on the next slide with the 7 statements to follow…

32. Elements
Compounds
Mixtures

33. Two or more substances that are physically mixed
Only one kind of atom; atoms are bonded if the element is diatomic or polyatomic
Two or more substances that are physically mixed
Substance with definite make up and properties
Cannot be physically separated
Can be physically separated
Two or more kinds of atoms
Two or more kinds of atoms that are bonded

34. AP Chem Mini Quiz
What is the difference between a qualitative observation and a quantitative observation? Give 3 example of each. QL are described in words like big, round, blue and QT are described with measurements like 200g, 2.5in in diameter and 34L.
What is an intensive property? These properties do not depend on how much of the substance you have…like water freezes at 0C.
What is an extensive property? These properties do depend on how much of the substance you have…like 25g of NaCl.

35. Elements, Compounds & Mixtures
Cannot be physically separated
Can be physically separated
Elements
Compounds
Mixtures
Only one kind of atom; atoms are bonded if the element is diatomic or polyatomic
Two or more substances that are physically mixed
Two or more kinds of atoms that are bonded
Substance with definite make up and properties
Two or more kinds of atoms