Section 1
Answer the following questions about alkali metals.
1.
How many outer electrons do their atoms have? ............................................................................
2.
Why do the alkali metals have to be stored in oil?
3.
What is formed when an atom loses an electron? ..........................................................................
4.
Give three ways that Group 1 metals are different from other metals.
.........................................................................
i)
...........................................................................................................................................................
ii)
...........................................................................................................................................................
iii)
...........................................................................................................................................................
5.
Which gas is made when alkali metals react with water? .................................................................
6.
How would you test for this gas? ........................................................................................................
7.
Complete each chemical equation.
a)
sodium (Na)
+
water
→
(H2O)
b)
potassium (……)
+
water
sodium hydroxide
+
(NaOH)
→
(……)
……………….
……………….
(H2)
+
……………….
……………….
……………….
(KOH)
c) ........................... (Li)
+
………
(H2O)
→
……………….
……………….
+
……………….
……………….
……………….
8.
In each of the above equations one of the substances will turn universal indicator from green
to purple, what does this tell us about the substance? ........................................................................
Group 1 – the alkali metals
Task 2
Before watching a demonstration of the reaction of alkali metals with water predict the following.
1.
Which metal’s reaction were you expect to be most vigorous? ......................................................
2.
Which one would be the least vigorous? .................................................................................................
3.
Suggest reasons for your answers to questions 1 and 2. ....................................................................
...........................................................................................................................................................................
Task 3
The table below gives data on some of the physical properties of the alkali metals.
Alkali
metal
Symbol
Lithium
Atomic
number
Atomic
mass
3
Sodium
Boiling point
o
C
Melting
point
o
C
Density
g/cm3
1342
181
0.535
880
98
0.971
63
0.862
Potassium
Rubidium
Rb
Caesium
Cs
688
133
671
1.53
28
1.87
a)
Complete the symbol, atomic number and atomic mass columns.
b)
Use the table to predict the boiling point of potassium. . ....................................................................
c)
Why did you choose this value? ................................................................................................................
d)
Use the table to predict the melting point of rubidium. ......................................................................
e)
Why did you choose this value? ................................................................................................................
...........................................................................................................................................................................
f)
Use the table and what you know about the reactivity of the alkali metals to make 4
generalisations about the trends in Group 1 metals.
i)
As you move down the table the ...................................................................................................
ii)
.................................................................................................................................................................
iii)
.................................................................................................................................................................
Group 1 – the alkali metals
iv)
g)
.................................................................................................................................................................
Suggest why the alkali metals become more reactive as you move down the table.
...........................................................................................................................................................................
...........................................................................................................................................................................
Worksheet from the experiment - Reactivity of Metals: Li, Na, and K
1. Why was it necessary to keep the quantity of alkali metal in the classroom to a minimum?
2. Why was it essential for all equipment that came in contact with the alkali metal samples to be coated
with mineral oil?
3. Why was lithium safer for students to use than potassium?
4. Why a safety shield required for the demonstration?
5. Why was phenolphthalein added to the water?
6. Explain why leftover pieces of metal must NOT be discarded in the trash or the sink.
7. What are possible fire hazards when working with the alkali metals?