Chemical Reactions Week 1 Day 1 Monday Chemical Reactions Text Notes and Demos
DSJ 4-6-15: Is adding blue food coloring to a liquid a chemical or a physical change? Justify
your reasoning.
DIRECTIONS: IP 151
Title: Chemical Reactions Notes
Notes are on IP 151
Pg. 271
Reactions
Pg. 272
Physical
changes
Chemical
Changes
Evidence
Pg. 273
Pg. 274
243
Pg. 288
Energy and
reactions
Pg. 289- Exothermic
291
reactions
Pg. 291- Endothermic
292
reactions
What happens to atoms to make chemical
reactions?
What are physical changes, give examples.
Terms: Reactants, Products
Explain what evidence we have for chemical
reactions. Please include the main idea from p.
243
Describe Bond Energy
Explain exothermic reactions. How do they feel,
what do they do, how would you recognize them?
Explain endothermic reactions. How do they feel,
what do they do, how would you recognize them?
DEMOS: Exothermic Reaction (Hot Snapz) Endothermic (Ammonium
Thiocyanate and Barium Hydroxide)
HOMEWORK: OP 151 - Draw a 2 square. Summarize endothermic and
exothermic reactions. (See Page 292 in science textbook)
https://www.youtube.com/watch?v=MyAzjSdc3Fc&noredirect=1 for
Endothermic Reaction
Notes are on IP 151
Pg. 271 Reactions
Pg. 272
Physical
changes
Pg. 273
Chemical
Changes
Pg. 274 Evidence
243
Pg. 288
Energy and
reactions
What happens to atoms to make chemical
reactions? Bonds between atoms are broken
or new bonds are formed. The new
arrangement of atoms is a completely
different substance
What are physical changes, give examples.
Changing from one state of matter to
another is a physical change, such as water
going from a solid state (ice) to a liquid
state (water)
Terms: Reactants, Products
Reactants are the substances present at the
beginning of any reaction. They are listed
to the left of the yields sign (arrow).
Products are the new substances that are
formed as a result of the reaction. They are
listed to the right of the yields sign
Reactants
Products
CH4 + O2 
CO2 + H2O
Explain what evidence we have for chemical
reactions. Please include the main idea from p.
243
Evidence is what we are able to see
1.
A new substance is formed that is
completely different from the
beginning substance
2. A change in color
3. A Precipitate is formed (this is a solid
formed, may appear as cloudiness
4. A gas is formed
5. A change in temperature (not from
heating
Describe Bond Energy
The energy that is formed when breaking or
forming new chemical bonds is called bond
energy
Pg. 289- Exothermic
291
reactions
Explain exothermic reactions. How do they feel,
what do they do, how would you recognize them?
If energy is released when a new product is
formed this is called exothermic reactions.
Exothermic reactions will feel hot to the
touch, may look like burning or explosions
In an equation energy is on the product side
of the equation
Pg. 291- Endothermic Explain endothermic reactions. How do they feel,
292
reactions
what do they do, how would you recognize them?
If energy is absorbed during a reaction this
is called endothermic reactions.
Endothermic reactions will feel cold to the
touch as they absorb the energy from your
hand. In an equation energy is on the
reactant side of the equation
Barium hydroxide –ammonium thiocyanate reaction seriously endothermic! Also
a great one for observations. Copy entire equation (both reactant and product
side) Can you identify each element in the equation? Look at your periodic
table!!
REACTANTS
Ba(OH)2.8H2O (s) + 2 NH4SCN (s) + energy
PRODUCTS
--> Ba(SCN)2 (s) + 10 H2O (l) + 2 NH3 (g)
To use this reaction as a demonstration:
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32g barium hydroxide octahydrate
17g ammonium thiocyanate (or could use ammonium nitrate or
chloride)
250 ml beaker
stirring rod
wood block or piece or card
thermometer-digital is good
some wet litmus paper if you want to show gas is basic
ammonium
Method:
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Smear some water over a wood block or piece of card or lab mat
Pour the barium hydroxide and ammonium thiocyanate into the beaker and stir.
The smell of ammonia should become evident within seconds. If you hold a piece
of wet litmus paper over the reaction mixture in the flask, you can see that the
gas produced by the reaction is basic.
Liquid will be produced, so the mixture will turn slushy as the reaction proceeds.
If you set the flask on a damp block of wood or piece of cardboard while
performing the reaction you can freeze the bottom of the flask to the wood or
paper. You can touch the outside of the beaker, but don't hold it in your hand –
better to have the digital thermometer giving the dramatic fall in temperature.
When you are finished, the contents of the flask can be washed down the sink
with plenty of water. Avoid skin contact. If you get any solution on your skin, rinse
it off straight away with water.
http://www.youtube.com/watch?v=yTzcoyzPQE0
is a nice video of this.