1. Matter, Properties & Changes CVHS Chapter 3

2. Chemical Properties The ability of a substance to combine with or change into one or more other substances is called a chemical property – Fe rusting – Fe doesn’t react w/ N 2 (g) – CH 2 O burning – Inability of a substance to change into another

3. Properties & States of Matter Every substance has its own unique set of chemical & physical properties Environment affects how matter reacts – Temperature – Pressure States (Physical property of a substance) – Solid – Liquid – Gas – Plasma (only on earth in lightening bolts)

4. Solids Has its own definite shape and volume Tightly packed – Expands slightly when heated – May not conform to shape of container b/c tightly packed

5. Liquids Flows Constant Volume Takes shape of its container Particles of liquid – Loosely packed – Not held in place – Able to slide past each other – b/c of way they are packed, virtually incompressible – Expand when heated

6. Gases Flows to conform to shape of container Fills entire container Particles very far apart – Compressible b/c of space between particles Gas: @ room temp. Vapor: liquid or solid at Room Temp. – Steam is a vapor b/c water is a liquid @ room temp.

7. Physical Changes A substance often undergoes changes that result in a dramatically different appearance yet leave the composition of the substance unchanged. An example is the crumpling of a sheet of aluminum foil or boiling a container of water.

8. Chemical Changes Chemical properties relate to the ability of a substance to combine with or change into one or more substances. A process that involves one or more substances changing into new substances is called a chemical change, which is commonly referred to as a chemical reaction. New substance formed has diff. composition & properties than the original substances Iron reacts w/ Oxygen to form rust

9. Chemical Changes Thus iron and oxygen are reactants and rust is a product. When you encounter terms such as explode, rust, oxidize, corrode, tarnish, ferment, burn, or rot, the meaning generally refers to a chemical reaction in which reactant substances produce different product substances The silver earring is oxidized: – Electrons are removed from the silver earring by sulfur in the air forming silver (II) sulfide – 2 Ag + S  Ag 2 S

10. Conservation of Mass Total mass of material before and after a chemical reaction is the same Scientists observed so often they called it THE LAW OF CONSERATION OF MASS

12. Practice Questions Identify each of the following as a property of a solid, liquid, or gas. Some answers will include more that one state of matter. flows and takes the shape of a container – Gas & Liquid Compressible – Gas made of particles held in a specific arrangement – Solid has definite volume – Solid & Liquid always occupies the entire space of its container – Gas has a definite volume but flows – Liquid

13. More Practice! Identify each of the following as an example of a chemical change or a physical change. A. Moisture in the air forms beads of water on a cold windowpane A. Physical B. An electric current changes water into hydrogen and oxygen. B. Chemical C. Yeast cells in bread dough make carbon dioxide an ethanol from sugar. C. Chemical

14. Still More Practice A reaction between sodium hydroxide and hydrogen chloride gas produces sodium chloride and water. A reaction of 22.85 g of sodium hydroxide with 20.82 g of hydrogen chloride gives off 10.29 g of water. What mass of sodium chloride is formed in the reaction? 33.38 g sodium chloride

15. Elements Pure substance, can’t be separated by physical or chemical methods All matter can be broken down into elements Each element has unique symbol & name – The chemical symbol consists of one, two, or three letters; the first letter is always capitalized and the remaining letter(s) are always lowercase.

16. Periodic Table As more elements were discovered over time, a need for organization became evident 1869: Mendeleev organized elements into columns & rows based on similarities & mass (had some errors) Current Periodic table – Organized by atomic # (protons) – Horizontal Rows: periods – Vertical Columns: groups or families Families have similar properties The table is called “periodic” because the pattern of similar properties repeats as you move from period to period.

17. Compounds Pure substance A combination of two or more different elements that are combined chemically – Water, table salt, sugar, aspirin – table salt, or sodium chloride, is composed of one part sodium (Na) and one part chlorine (Cl), and its chemical formula is NaCl – Water is composed of two parts hydrogen (H) to one part oxygen (O), and its formula is H 2 O Can be broken down into simpler substances by chemical reactions

18. Compounds Can be broken down into simpler substances by a chemical reaction Compounds are usually more stable than their individual component elements Compounds have different properties than their constituent elements – H 2 & O 2 are gases – H 2 O is a liquid Separation requires external energy – Heat – electricity

19. Law of Definite Proportions A compound is always composed of the same elements in a definite proportion by mass Mass of compound = the sum of the masses that make up the compound The ratio of the mass of an element to the mass of the compound is:

20. % Composition Practice A 134.50-g sample of aspirin is made up of 6.03 g of hydrogen, 80.70 g of carbon, and 47.77 g of oxygen. What is the percent by mass of each element in aspirin? 4.48% hydrogen, 60% carbon, 35.52% oxygen A 2.89-g sample of sulfur reacts with 5.72 g of copper to form a black compound. What is the percentage composition of the compound? 33.6% sulfur, 66.4% copper

21. Law of Multiple Proportions The law of multiple proportions states that when 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. ratios express the relationship of elements in a compound

22. Law of Multiple Proportions Hydrogen Peroxide (H 2 O 2 ) & Water (H 2 O) Each compound contains the same elements (hydrogen and oxygen). Hydrogen peroxide differs from water in that it has twice as much oxygen When we compare the mass of oxygen in hydrogen peroxide to the mass of oxygen in water, we get the ratio 2:1 H2O2H2O2 H2OH2O

23. Yipeeeee! More Practice Identify each of the following as an example of a homogeneous mixture or a heterogeneous mixture. 70% isopropyl rubbing alcohol – homogeneous a pile of rusty iron filings – heterogeneous Concrete – heterogeneous Saltwater – homogeneous Gasoline – homogeneous Bread – heterogeneous

24. I’m so excited, even more practice! Identify each of the following as an example of an element or a compound. Sucrose (table sugar) C 12 H 22 O 11 – compound The Helium (He) in a balloon – Element Baking Soda (NaHCO 3 ) – Compound A Diamond (C) – Element