2. HOW DOES ONE STUDY FOR A
LAB?
Practice with the tools, e.g. thermometer, scales, weighing
tray, stopwatch, calculators
Practice making graphs, especially line graphs (x: time, y:
temperature), using data tables
Memorize the definitions of key science words
Review lab reports (Googledocs)
Use other sources for quizzing, e.g.
BrainPop, aboutChemistry.com
Make own quiz/test
Have a peer/parent quiz you on definitions/method
3. KEY WORDS: CHEMICAL
CHANGE
Precipitate (product Temperature change
with different during reaction
properties)
• Exothermic lab
• Magnesium Carbonate lab • Endothermic lab
Gas released (new
Color Change substance)
• Blue Bottle lab • Law of Conservation of
Mass lab
Chemical • Dissolving Berocca tablet
change
4. chemical change
A chemical reaction is a chemical change which forms new substances;
the starting materials (reactants) are different from the product
When a chemical change takes place there is the change of
temperatures where there might be loss of heat but in most chemical
change reactions heat or energy is produced.
Another characteristic of a chemical change is the change in color. For
example when an iron nail comes into contact with water, the nail
begins to rust and its color change from silver to reddish brown
meaning that chemical change has taken place.
The production of gases and solids is also another characteristic of a
chemical change. The gases produced appear in the form of bubbles as
a result of the reaction. A solid maybe formed and it separates itself
from the solution after the reaction.
6. Endothermic reaction
An endothermic reaction is any chemical reaction that absorbs
heat from its environment. It is a reaction that requires energy to
proceed. The intake of energy may be observed as a decrease in
temperature as the reaction proceeds. Once the reaction is
complete, the temperature of the mixture will return to room
temperature.
Examples
1. reacting acetic acid with sodium carbonate
2. photosynthesis (chlorophyll is used to react carbon dioxide plus
water plus energy to make glucose and oxygen)
7. Exothermic reaction
Many chemical reactions release energy in the form of
heat, light, or sound. These are exothermic reactions.
Exothermic chemical reactions produce heat.
Examples
1. In this reaction vinegar is used to remove the protective coating
from steel wool, allowing it to rust. When the iron combines with
oxygen, heat is released.
8. Collecting Data
Endothermic Exothermic
Initial Temperature °C °C
Final Temperature °C °C
Temperature change
rate
11. Law of Conservation of Mass
Matter cannot be created nor destroyed, but it can be
transformed in shape, state and volume.
the mass of substances produced (products) by a chemical
reaction is always equal to the mass of the reacting
substances (reactants) in a closed system.
Example
1.00g carbon + 5.34g sulphur 6.34g carbon disulphide
12.
13. CHEMICAL CHANGE PHYSICAL CHANGE
In a chemical change where there is a A physical change in a substance doesn't
chemical reaction, a new substance is change what the substance is.
formed and energy is either given off or
absorbed.
If a piece of paper is burned, it is broken up For example, if a piece of paper is cut up into
into different substances that are not paper. small pieces it still is paper. This would be a
physical change in the shape and size of the
paper.
Chemical changes cannot be reversed with Physical changes can be reversed.
the substance changed back without
extraordinary means, if at all.
If one made a recipe for a cake with flour, If one decided to mix sugar/salt into water
water, sugar and other ingredients and to make sugar/salty water, this would be a
baked them together, it would take physical change as the water could be left
extraordinary means to separate the various out to evaporate and the sugar/salt crystals
ingredients out to their original form. would remain.
Note: remember salt is sodium chloride
(NaCl)
