Question 6

Question

Are the following examples of chemical or physical changes?

Column A
1.
A silver spoon tarnishing:
A silver spoon tarnishing
2.
Blowing a dandelion:
Blowing a dandelion
3.
Building a sand castle:
Building a sand castle
4.
Toasting bread:
Toasting bread
Column B
a.Physical change
b.Chemical change
Question 7
Looking at the periodic table, determine the number of valence electrons present in Phosphorous (P).

a
5 valence electrons
b
2 valence electrons
c
4 valence electrons
d
3 valence electrons
Question 8
How many valence electrons are in Oxygen?

a
3
b
1
c
6
d
4
Question 9
Balance the following the chemical equation:

_ Na2O + _ CaBr2 → _ NaBr + _ CaO

a
1:1:1:2
b
2:1:1:1
c
1:1:2:1
d
1:2:1:1
Question 10
Balance the following the chemical equation:

_ Mg + _ F2 → _ MgF2

a
1:2:1
b
2:1:1
c
1:1:2
d
1:1:1
Question 11
Which statement correctly compares synthesis and decomposition reactions?

Meme Creator - Funny at least I know the difference between ...

a
Synthesis and decomposition reactions are opposites of each other. Synthesis reactions are in the form AB → A + B, while decomposition reactions are in the form A + B → AB.
b
Synthesis and decomposition reactions are opposites of each other. Synthesis reactions are in the form A + B → AB, while decomposition reactions are in the form AB → A + B.
c
Synthesis and decomposition reactions are both neutralization reactions. Synthesis reactions are in the form AB → A + B, while decomposition reactions are in the form A + B → AB.
d
Synthesis and decomposition reactions are both neutralization reactions. Synthesis reactions are in the form A + B → AB, while decomposition reactions are in the form AB → A + B.

Answer 1

Here are the answers to your questions:

Question 6: Are the following examples of chemical or physical changes?

1. A silver spoon tarnishing: b. Chemical change (this involves a reaction with sulfur compounds in the air).
2. Blowing a dandelion: a. Physical change (this is a change in shape/size, not a chemical makeup).
3. Building a sand castle: a. Physical change (the sand is just rearranged, no new substances are formed).
4. Toasting bread: b. Chemical change (this involves Maillard reaction and changes the chemical composition of the bread).

Question 7: Determine the number of valence electrons in Phosphorus (P).

• a. 5 valence electrons (Phosphorus is in group 15 of the periodic table, which has 5 valence electrons).

Question 8: How many valence electrons are in Oxygen?

• c. 6 (Oxygen is in group 16 of the periodic table, which has 6 valence electrons).

Question 9: Balance the following chemical equation: _ Na2O + _ CaBr2 → _ NaBr + _ CaO

• d. 1:2:2:1 (Balanced equation: 1 Na2O + 2 CaBr2 → 2 NaBr + 1 CaO).

Question 10: Balance the following chemical equation: _ Mg + _ F2 → _ MgF2

• a. 1:2:1 (Balanced equation: 1 Mg + 2 F2 → 1 MgF2).

Question 11: Which statement correctly compares synthesis and decomposition reactions?

• b. Synthesis and decomposition reactions are opposites of each other. Synthesis reactions are in the form A + B → AB, while decomposition reactions are in the form AB → A + B.

Feel free to ask if you have any further questions!