4.1- Writing and Balancing Chemical Equations - The Magic of Chemistry

Question 1

What aspects of a chemical substance does a physical change affect?

Answer 1

It’s form, but not its composition (doesn’t make new substances).

Question 2

What is the most common physical change?

Answer 2

Changes of state.

Question 3

Name three physical changes other than changes of state:

Answer 3

• Dissolution
• Ferromagnetism
• Tempering

Question 4

What do you call it when a solute dissolving in a solvent still reforms when you remove the solvent?

Answer 4

Dissolution.

Question 5

What do you call it when a material forms a permanent magnet without changing chemical composition?

Answer 5

Ferromagnetism

Question 6

What do you call it when the toughness of iron-based alloys is increased allowing them to better deform without breaking?

Answer 6

Tempering.

Question 7

What is the difference between liquid state and aqueous solution?

Answer 7

A substance is only in the liquid state if it melted from solid.

Question 8

What do you call the starting materials that react during a chemical reaction?

Answer 8

Reactants.

Question 9

What do you call the new materials formed by the chemical reaction?

Answer 9

Products.

Question 10

What is evidence that a chemical reaction took place?

Answer 10

• The reaction absorbed or released energy.
• Change of colour.
• Gas forms (bubbles)
• One of the products is solid and sinks to bottom of container.

Question 11

What do you call an insoluble solid that forms from the reaction of two transparent aqueous solutions?

Answer 11

Precipitate.

Question 12

If the precipitate of a solution remains suspended, what is the solution?

Answer 12

A colloid.

Question 13

If the precipitate of a solution sinks to bottom, what is the solution?

Answer 13

A suspension.

Question 14

What is a system that does not allow anything to enter or leave?

Answer 14

Closed system.

Question 15

What is a system that allows things to enter or leave?

Answer 15

Open system.

Question 16

What do you call the law that says in a closed system, total mass does not change?

Answer 16

Law of conservation of mass.

Question 17

If mass is conserved during a chemical change, what other things must therefore be conserved?

Answer 17

• Atoms
• Charge
• Energy

Question 18

What law says in a closed system, the total number and type of atoms does not change during a chemical reaction?

Answer 18

Conservation of atoms.

Question 19

What law says that in a closed system, the total electrical charge does not change during a chem reaction?

Answer 19

Conservation of charge

Question 20

What law says in a closed system, the total amount of energy doesn’t change?

Answer 20

Conservation of energy.

Question 21

A balanced equation ensures what?

Answer 21

The conservation of mass, atoms and electrical charges.

Question 22

Why is conservation of energy nearly impossible in a chemical reaction?

Answer 22

No one has yet prevented all energy transfer.

Question 23

What do you call the numbers written before the formula of each reactant and product representing how many particles of each element are present?

Answer 23

Coefficients.

Question 24

What are the simple steps of balancing an equation?

Answer 24

• Count elements on each side
• Determing which need to be balanced
• Simpler first
• Leave H O and H2O until end.
• Save lone elements for the end.
• Start with metal.
• To change from odd to even, double all elements.