Chapter 1: Introduction to Matter *Differentiate between elements, compounds and mixtures *Explain how materials are characterized by having a specific density. *Identify atoms as the basic building blocks of matter- elements are composed of only one type of atom. *List the 5 parts (pg. 31) of Dalton’s Atomic Theory *Be able to solve Density and Constant Ratio Problems on test

1. CHP. 1 - INTRODUCTION TO MATTER Matter is anything that has mass and takes up space. Everything in the universe is made up of matter.

3. Characteristic Property – a quality that NEVER changes & so can be used to identify a particular type of matter While some properties can change (ex: size or shape of a piece of wood), characteristic properties remain the same EVERY sample of a particular kind of matter will have the same characteristic properties An unknown sample of matter can then be identified by looking at its characteristic properties

4. Common Characteristic Properties used in Testing Unknowns: Boiling Point – the temperature at which a liquid boils is characteristic for each kind of substance. Ex: pure water always boils at 1000 C Liquids that may look alike can be identified by testing their boiling points Melting Point – the temperature at which a solid melts is characteristic for each kind of substance

5. Identification of an unknown substance requires comparing at least 2 characteristic properties for a match This is necessary since different substances may share one characteristic property

6. Changes in Matter – two types: Physical Changes alter the form or appearance of a substance, but do not change its identity. Chemical Changes cause a substance to break apart (or combine with other substances) to form something new.

7. Classifying Matter: Two Categories Based on Composition Mixture – when 2 or more kinds of matter are placed together, but are NOT chemically combined into one substance; this means each kind of matter keeps its own properties; often they can easily be separated. A) Solution – a mixture that is so well mixed that the individual kinds of matter can’t be distinguished B) Suspension – a mixture in which different kinds of matter can be seen separately. Ex: oil & vinegar Pure Substance – made of only ONE kind of matter with 1 set of properties; Ex: elements or compounds

Solutions Don’t Have to be Liquids Often man has found it useful to melt down 2 or more pure metals and mix them together. Once they have been thoroughly stirred and then allowed to harden, we call this solid solution of metals an alloy Ex: copper + tin makes bronze Ex: copper + zinc makes brass Ex: copper + silver makes sterling silver

8. Element – one kind of pure substance Elements cannot be broken down into simpler substances There are over 100 elements known at present Many familiar elements are metals while some are nonmetals Elements are abbreviated with 1 or 2 letter symbols (always starting with a capital letter)

9. Compounds – matter consisting of 2 or more elements that are chemically combined to form one pure substance The properties of a compound are different from the properties of the elements it contains Ex: Sodium is an explosive metal, and chlorine is a poisonous gas, but when combined to make sodium chloride (table salt) they become harmless and edible Compounds are abbreviated with element symbols and subscript numbers: H2O (water) CO2 (carbon dioxide)

10. Ways of Measuring Matter Weight – a measure of the force of gravity pulling you downward against a scale; this quantity will change depending on the pull of gravity Mass – NOT the same as weight; it is a measure of the amount of matter contained in an object

11. Standardized Measurement Weight and Mass are measured in units called grams Volume is measured in units called either cubic centimeters (cm3) for solids or milliliters (ml) for liquids 1 cm3 is a volume equal to 1 ml

13. Density - another way to measure matter Density is a measure of how much mass of a substance is contained in a certain volume Density has to be calculated by comparing mass and volume: Density = Mass Volume (Think of “Department of Motor Vehicles” – DMV)

14. Comparing Densities If a great deal of matter is packed into a small space, this gives a very high density value If the matter is more loosely packed the density value is low Water has a density of 1 g/ml (meaning there is 1 gram of water per each 1 milliliter)

15. Density is a characteristic property Density is the same for all samples of a substance Ex: pure gold always has a density that measures 19.3 g/cm3 Since density remains the same, it can be used to identify types of matter Gold bars Tiny gold nuggets

16. The Smallest Possible Particles of Matter An atom is the smallest particle of an element that keeps all the properties of that substance Back in 440 B.C. Democritus gave us the name atom; it is taken from the Greek “atomos” meaning uncuttable

17. Scientific Ideas About Atoms In 1802 John Dalton carried out experiments with elements and recorded his conclusions Today we refer to his ideas as the Atomic Theory as listed here: a) Atoms cannot be broken into smaller pieces b) In any single element, all the atoms are exactly alike c) Atoms of different elements are different

18. (Atomic Theory Continued) d) Atoms of 2 or more elements can combine to form compounds e) Atoms of each element have a unique mass f) The masses of the elements in a compound are always in a constant ratio

19. Combining Atoms to make Compounds A molecule is a group of atoms that are joined together to act as a single unit; this molecule is the smallest piece of a compound A chemical bond is the force that holds the atoms of the molecule together

20. Atomic Models Today we have scanning tunneling microscopes that can show us tiny images such as gold atoms

21. Separating Elements from the Earth for Our Use Only a few elements can be found in a pure form in the Earth In 1848 John Sutter found several gold nuggets in the river near his mill; this discovery sparked the California gold rush Prospectors used the high density of gold to separate dust and nuggets from the stream bed by “panning”

22. Another Separation Technique Most elements cannot be found in their pure state Ore is any rock that contains useful metals combined with other substances Ores are mined from the Earth and then a complex series of steps is used to isolate the useful metal The last step in this process is called electrolysis which means “electric cutting”

Pure Substances – cannot be easily broken down Element – just one kind of matter Compound – grouping of 2 or more elements Atoms (smallest individual pieces) Molecule of an Element (chemical bonding of the same kind of atoms) Molecule of a Compound (chemical bonding of different kinds of atoms)