Grade 8: Rearranging Atoms

5.5 Rearranging Atoms

From Chapter 05: Reactivity
Cambridge Lower Secondary Science Stage 9

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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

Poll

BUT FIRST...

Which of the five basic emotions do you most relate to right now? Be ready to share and explain your answer.

Dropdown

In the reaction, the substances that are arrow is pointing to are the​

Select answer

​while the substances on the other side of the arrow are the ​

Select answer

.

Multiple Choice

Is the number of magnesium atoms the same on each side of the equation (reactants and products)?

• YES

• NO

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

Match

Look at the reaction between sulfuric acid and calcium carbonate.

sulfuric acid + calcium carbonate -> calcium sulfate + water + carbon dioxide

Which one is the:

• REACTANT that contains hydrogen

• REACTANT that contains carbon

• PRODUCT that contains calcium?

• PRODUCT that contains hydrogen

• PRODUCT that contains carbon

H₂SO₄

CaCO₃

CaSO₄

H₂O

CO₂

• H₂SO₄

• CaCO₃

• CaSO₄

• H₂O

• CO₂

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.

Open Ended

Make a hypothesis (educated/smart guess, not magic) why the mass increased when the iron wool was burned.

Why do you think the mass increased?

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.

Multiple Choice

Zara, Safia, and Arun have different ideas about what will happen to the mass in the flask as the reaction is taking place. Who do you think is correct?

• Safia is correct. The mass will decrease.

• Zara is correct. The mass will increase.

• Not enough information to determine who is correct
• Arun is correct. The mass will stay the same.

Multiple Select

In the reaction between calcium carbonate and hydrochloric acid with the word equation being:

Calcium Carbonate + Hydrochloric Acid -> Calcium Chloride + Water + Carbon Dioxide

Which TWO of the products contain the element OXYGEN?

• calcium carbonate
• hydrochloric acid

• calcium chloride

• water

• carbon dioxide

Open Ended

What could Arun have done to show that mass is conserved in a chemical reaction?

​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

Multiple Choice

ENDOTHERMIC or EXOTHERMIC:

Aluminum + Oxygen -> Aluminum Oxide + 1601 kJ (energy)

• ENDOTHERMIC

• EXOTHERMIC

Multiple Choice

ENDOTHERMIC or EXOTHERMIC:

Phosphorus Pentachloride + 886J -> Phosphorus + Chlorine

• ENDOTHERMIC

• EXOTHERMIC

Multiple Choice

ENDOTHERMIC or EXOTHERMIC:

2 Cu + Cl₂ -> 2 CuCl + 136 kJ

• ENDOTHERMIC

• EXOTHERMIC

Multiple Choice

ENDOTHERMIC or EXOTHERMIC:

2 CO₂ + 3 H₂O + heat -> CH₃COCH₃ + 3 O₂

• ENDOTHERMIC

• EXOTHERMIC

Multiple Choice

ENDOTHERMIC or EXOTHERMIC:

Explosion of a fire cracker triggered by a spark

• ENDOTHERMIC

• EXOTHERMIC

Multiple Choice

ENDOTHERMIC or EXOTHERMIC:

Burning of coal

• ENDOTHERMIC

• EXOTHERMIC

Multiple Choice

ENDOTHERMIC or EXOTHERMIC:

Lead chloride dissolves only in hot water

• ENDOTHERMIC

• EXOTHERMIC

Multiple Choice

ENDOTHERMIC or EXOTHERMIC:

Heat causes sodium bicarbonate to decompose

• ENDOTHERMIC

• EXOTHERMIC