1. Warm-up: Identify… A: substance or mixture (homogenous/heterogeneous) B: if it’s a substance further identify as element or compound
Silver
Salt water
Air
Oil in water
Water
Helium gas

2. Ch. 2.3 Elements and Compounds

3. 1. Elements
Def: simplest form of matter with unique set of (intensive) properties
Listed in the Periodic Table
1 or 2 letters: first capital (usually the first letter of the common name), second lower case (if two elements start with the same letter)

4. Practice Hydrogen: H Helium: He
What are the symbols for Neon, Nickel, Nitrogen who gets the N?

5. 2. Compounds
Def: Chemical combination of two or more elements in whole number ratios
Example: H2O
Subscript numbers refer to the element in front
Actually should be written: H2O1
Ratio: 2 x H : 1 x O but 1 is never written in Chemistry!

6. Practice: Give the ratio of elements in…
H2 Ratio: 2 x H H2O2 Ratio: 2 x H: 2 x O C6H12O6

7. Practice: Elements change characteristics when combined into compounds!!!
Example: NaCl Na is a silvery metal, soft, explosive Cl is a green colored, aggressive gas NaCl is ____________________

8. Ch. 2.4 Chemical Reactions

9. Chemical Property Def: Ability to undergo certain chemical Rx Example:
Iron binds oxygen to form rust
Therefore: ability to rust is a chemical property of iron
Fe + O → FeO (rust)
Gold does not have this
property! Gold does not
rust!

10. Indicators of Chemical Rx
If you mix two substances and you observe any one or more of the following….
Heating or cooling
change in color
Sound, explosions, light
gas bubbles
formation of a precipitate
….then a chemical Rx took place
Note: Every chemical change always involves a transfer of energy which is often invisible

11. Law of the Conservation of Mass
Matter cannot be created or destroyed in a chemical Rx
But it often changes shape, consistency, state of matter but
The mass of the product(s) must always equal the mass of the reactant(s)
Note: if product weighs less, matter in form of gas has escaped!

13. Properties of Matter
Properties of Matter

14. Warm-up
List all characteristics you observed that are general markers that a chemical Rx had taken place during the Tic Tac Lab
Write the Rx with reactants and products – use words since we do not know the exact formula for each