Download in a chemical reaction you combine reactants

ALWAYS:
• Wear goggles
• Wear lab gear
• Hair up
• Wear closed shoes
• NO playing
• Monitor experiments
• Check before turning the gas on
• Call the teacher if there is a problem – IMMEDIATELY
• Know where safety gear is
• Rinse off chemical simmediatley
• Follow all directions
SAFETY
http://elearning.flinnsci.com/StandalonePlay
er.aspx?vid=Whoosh Bottle Safety.flv
CHEMICAL REACTIONS
chemical reaction
reactant
product
physical change
chemical change
chemical equation
mitochondria
chloroplast
exothermic
endothermic
You should be able to
identify and describe the
following:
• a chemical reaction
• the difference between
a chemical and
physical change
• the components of a
chemical equation
• exothermic versus
endothermic reactions
VOCABULARY & GOAL
CHEMICAL CHANGES
During this change the
substance made is
chemically different from
what you started with
The change cannot be
reversed
Clues:
 Smoke
 Sound
 Color change
 Gas is produced
PHYSICAL CHANGES
There is a
 change in size or shape
 change in state (solid,
liquid, or gas)
The change can be
reversed
CHEMICAL VERSUS
PHYSICAL CHANGES
YOUR TURN: PHYSICAL OR CHEMICAL CHANGES
EXPLAIN YOUR REASONING.
1. Glass breaking
2. Hammering wood together to make a house
3. Spoiling food (what happens when you have milk for too
long)
4. Melting butter
5. Burning toast (bread in the toaster for too long)
6. Cutting grass
7. Digestion of food
8. Mixing salt and water
• occurs when ingredients combine, interact, are
rearranged, and new substances are made.
• More scientifically: in a chemical reaction you combine
reactants (the original ingredients) to create a final
product (what you get at the end of the chemical
reaction)
• A chemical change has occurred.
CHEMICAL REACTION
CHEMICAL EQUATION
describes the reactants and products of a chemical
reaction
Reactants -the chemicals you start with & are written on
the left side of the chemical equation
Products - the chemicals that are made & are written on
the right side of the chemical equation
INGREDIENTS
• Reactants and products can be elements,
compounds, or mixtures.
• An element is an atom. More on these later.
• A compound is made of more than one element
bonded together. More on these later.
• A mixture is made of elements and/or compounds
stirred together but not bonded
THERM – MEANS HEAT OR ENERGY
EXOTHERMIC
Exo- means out or to exit
In an exothermic reaction –
energy is released.
Temperature of the
surroundings increases
(feels hot)
Light may be emitted
Why? When atoms bond
together they release heat
ENDOTHERMIC
Endo –means inside or to
enter
In an endothermic reaction –
more energy is absorbed
than released
Temperature of the
surroundings decreases
(feels cold)
Why? Atoms need to absorb
heat to break their bonds
http://www.youtube.com/watch?v=p-27I_osoaw
YOUR TURN – IDENTIFY EACH AS ENDOTHERMIC OR
EXOTHERMIC REACTION AND EXPLAIN YOUR REASONING
Activity
Endothermic or Exothermic? Why?
making ice cubes *
melting ice cubes *
cooking an egg
burning wood
Liquid water turning into steam (evaporation) *
rusting iron
* = not a chemical reaction
PRE-LAB INFORMATION
1. How to measure pH to see if a liquid is an acid or alkaline
a) Use a glass rod to take out a small sample of the
liquid
b) Transfer the sample to the litmus paper
c) Wait 30 seconds
d) Compare color to sheet
e) Record pH and whether the liquid is acid (pH < 7),
neutral (pH = 7), or alkaline (pH >7)
2. Safety
a) Goggles, lab coat, and hair up
Chemical Equation:
Identity the Reactants
Elements, compounds, or
mixtures?


Color of litmus paper
Acid or alkaline?
Brief description of the
method
Observations: sight, smell,
feel, etc.
Was this an exothermic or
endothermic reaction? How
did you know this?
Did a physical or chemical
change occur during this
reaction? How do you know?
Identity the Products
HW: read pages 7-8 in packet
describing common chemical
reactions and balancing
equations