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LETTING YOU KNOW THAT I WILL KNOW:

5.5 Rearranging Atoms

At the end of our session, I will be sent a log file (Microsoft Excel file) of the list of activities each student is doing while we were having our session.

- look at the rearrangement of atoms in chemical reactions
- learn what happens to the mass of reactants and products in a reaction
- learn what happens to the energy involved in chemical reaction

In this lesson, we will:

5.5 Rearranging Atoms

In this example, we can see two ways a chemical reaction is written:

CHEMICAL EQUATION Mg + HCl -> MgCl₂ + H₂
WORD EQUATION magnesium + hydrochloric acid -> magnesium chloride + hydrogen

The Law of Conservation of Matter says that the amount of matter stays the same, even when matter changes form. Sometimes it may seem that matter disappears during an experiment, but this law tells us that matter cannot magically appear or disappear, it simply changes from one form to another.

It is not MAGIC why the mass increased when the iron wool was burned. It is actually a very simple chemical reaction.
IRON reacted with OXYGEN in the air, forming IRON OXIDE.

The word equation is as follows:
IRON + OXYGEN -> IRON OXIDE

The additional mass came from oxygen.

​A reaction is EXOTHERMIC if more energy is released than absorbed.
Energy can be released often in the form of light or heat

Exothermic: energy is released
- Exo- = “exit” because heat exits from the object
- Seen in the chemical reaction of burning wood
- Temperature increases
- Feels HOT

​REACTANTS ---> PRODUCTS + ENERGY
or
REACTANTS ---> PRODUCTS + HEAT

​A reaction is ENDOTHERMIC if more energy is absorbed than released.

Endothermic: energy is absorbed
- Endo- = “enter” because heat goes into the object
- Seen in the chemical reaction of cooking
- Temperature of surrounding area decreases
- Feels COLD

​REACTANTS + HEAT ---> PRODUCTS
or
REACTANTS + ENERGY ---> PRODUCTS
or
REACTANTS ---> PRODUCTS