1. Types of Changes Physical change:
the shape, phase, size, etc. of the material can change
the material itself is the same before and after the change
The change can be “undone”
Chemical change:
The substances present at the beginning of the change are not present at the end
new substances are formed.
The change cannot be “undone.”

2. Review: Examples of Physical Changes
water evaporates
butter melts
a can is crushed
glass is broken
modeling clay is shaped
ripping paper
boiling water
sawing wood
breaking a stick
dissolving salt in water

3. Review: Physical Properties
describe the object or substance
can be observed or measured without changing the identity of the substance

4. Review: Examples of Physical Properties
color
odor
size
shape
state (solid, liquid, gas, plasma)
texture (smooth, rough, soft, bumpy)
density (measured in g/ml and g/cm³)
melting point/boiling point/freezing point

5. Review: Chemical Properties
are determined by the arrangement of atoms in the molecules making up the object
describe a object or substance based on its ability to change into a new substance with different properties
cannot be observed with your senses; must be tested
aren’t as easy to observe as physical properties

6. Key Idea #7
Chemical changes occur when elements and/or compounds react or decompose to produce new substances.

7. Chemical Properties
If the chemical properties of an object or substance
have changed, then a chemical reaction has occurred.
Examples of Chemical Properties:
pH: a measure of how acidic something is
Flammability: a substances ability to burn
Reactivity: The rate at which a substance reacts

8. Clues that indicate a chemical change has taken place include:
color change
temperature change
bubbling and fizzing
note: boiling water is NOT a chemical change
heat, light, or smoke is given off
a solid (precipitate) is formed
the change is difficult or impossible to reverse

9. Copy the following chart into your notes:
Compare and contrast the chemical properties of the new substance with the original after a chemical change.
Copy the following chart into your notes:
Examples
Properties before
Properties
after
Evidence of a chemical change
Bike
Hair
Alka Seltzer and water
Fireworks

14. In a chemical change
one or more substances combine or break apart to form new substances.
atoms rearrange themselves during a chemical reaction to form different molecules and compounds.
For example, when hydrogen reacts with oxygen the product is water vapor.

15. Baking Soda and Vinegar
Acid-base reaction.
Vinegar (acetic acid): C2H4O2
Baking soda (sodium bicarbonate): NaHCO3
C2H4O2 + NaHCO3 ---> C2H3O2Na + H2CO3
The products are sodium acetate and carbonic acid
Carbonic acid quickly decomposes into carbon dioxide and water: H2CO3 ---> H2O + CO2
The CO2 is what you see foaming and bubbling in this reaction.

16. Burning Sugar Add heat Add more heat C12 H22O11 = Carbon + Water (H2O)
Carbon + Water (H2O) = Carbon + Water Vapor (H2O)
Carbon + Hydrogen gas + Oxygen gas

17. Activation Energy is the energy needed to start a chemical reaction.
Example:
A match won't light spontaneously.
When you strike a match you are providing the activation energy needed to cause a reaction between the chemicals in the match head and oxygen in the air.

18. All chemical reactions include a change in energy.
Exothermic reactions release energy to their surroundings; usually in the form of heat.
Endothermic reactions need to absorb heat from their surroundings to proceed.

19. Conservation of Mass Mass is conserved during chemical changes.
The mass of the reactants is always the same as the mass of the products after the chemical reaction.

20. In every chemical change
new substances are formed
the starting substances are called the reactants
the new substances are called the products

21. Natural gas is primarily methane. 
Methane (CH4) is a molecule in which 4 hydrogen atoms are bonded to one carbon atom. 
Lighting a gas stove provides the activation energy that causes the methane to react with oxygen in the atmosphere and release heat.
During the reaction, the atoms recombine to form carbon dioxide and water vapor.

22. During a chemical change
the number and kind of atoms in the reactants are the same as the number and kind of atoms in the products.

23. After the chemical change the mass of the reactants equals the mass of the products.
Before the reaction there were 9 atoms
1 carbon, 4 hydrogen, 4 oxygen
After the reaction the same 9 atoms were there, just in a different combination.
                                  

24. Iron reacts with oxygen in the air to form rust.

25. After the chemical change
the new substances have different physical and chemical properties than the original elements and/or compounds.
the number and kind of atoms in the reactants are the same.

26. Pennies get dull over time because the copper in the pennies slowly reacts with the oxygen in the air to form copper oxide.

27. Chemical reactions cause chemical changes.
involve a change in substances and a change in energy.
cause atoms to rearrange themselves to form different molecules and compounds.
NOTE: Matter and energy is NOT created or destroyed in a chemical reaction---only changed.

28. The only sure evidence for a chemical reaction is
the production of new materials.

29. Chemical Reaction Examples
A sparkler contains magnesium.
When lit, the magnesium reacts with oxygen in the air and produces light and heat. 
The chemicals inside a rocket, when lit, react with the oxygen in the air and produce heat, light and sound.

31. Alka Seltzer and Water Ingredients: Water = H2O
Alka Seltzer = Sodium Bicarbonate 3(NaHCO3) + Citric Acid C6H807
Reactants:
Alka Seltzer + Water = [3(NaHCO3) + C6H807] + H2O
Products:
Water Vapor + Carbon Dioxide (in air) + Sodium Citrate + Water (in beaker) = 3(H2O)+ 3(CO2) (in air) + C6H5Na3O7+ H2O (in beaker)

32. Open vs Closed Systems
Open system: matter interacts with its surroundings; can be transferred in and out
Closed system: no matter is transferred in or out of the system

33. Examples of Chemical Changes
When a substance chemically changes, it becomes a different substance with different properties but the amount of matter remains the same (Conservation of Mass).
Examples of Chemical Changes
Burning sugar
Baking bread
Rusty nail
Fireworks exploding
Raw egg becomes cooked egg
Spoiled milk
Digesting food in your stomach
Cake mix becomes cake
Paper becomes ash

34. Why is a melting ice cube NOT an example of a chemical change?
Give at least three pieces of evidence in your answer.

35. Alka Seltzer Lab

36. Why is baking a cookie an example of a chemical change?
Give at least three pieces of evidence in your answer.

37. Chemical Properties and Chemical Change