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Reaction of Alkali Metal with Water Lab Answers

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Reaction of
Alkali Metals
with Water
Observations
Li
Appear
Hardness
Behaviour
Splint
Litmus
Na
Shiny / Lustre
Soft
Softer
floats/surface, melts,
bubbles/moves/fizz
Pop
Blue/base
K
Softest
Flame
Nothing
Answers to Questions 1-4
1. K was most reactive, Li was least.
2. Li
Na
K
3p+
4n0 2 1
11p+
2 81
0
12n
19p+
2 881
0
20n
3. The outer electron. Because positive and
negative charges attract, but this attraction
decreases with distance (like magnets).
4. K was most reactive because it’s outer
electron is further away and thus easier to
remove. Li is least reactive because its outer
electron is closer and harder to remove.
Answers to Questions 5-7
5. Rb, Cs, or Fr is more reactive
There is not one that is less reactive
6. Litmus tested for hydroxide
A flaming splint tested for hydrogen gas
7. The K beaker did not react because the
hydrogen was already used up
Misconceptions
3. Electrons are attracted to protons with an
electrostatic force, not magnetism or gravity.
4. K is not more reactive than Li because it has
more electrons, it is because it’s outer
electron is further from the nucleus.
7. CO2 is not a product when a metal burns or
when H2 burns, only when the original
substance contains C. In this case H2 was
burning and producing H2O. Excess N2 and
no H2 (or O2) can explain the splint going out.
Observations
Li
Appear
Hardness
Behaviour
Splint
Litmus
Na
K
Shiny / Lustre (1)
Soft
Softer
Softest (1)
floats/surface, melts,
Flame (1)
bubbles/moves/fizz (3)
Pop (1)
Nothing (1)
Blue/base (1)
Mark: /9
Answers to Questions 1-4
1. K was most reactive, Li was least (1)
2. Li
Na
K
3p+
4n0 2 1
11p+
2 81
0
12n
19p+
2 881
0
20n
(1)
(1)
(1)
3. The outer electron (1). Because positive and
negative charges attract, but this attraction
decreases with distance (like magnets).
4. K was most reactive because it’s outer
electron is further away and thus easier to
remove. Li is least reactive because its outer
electron is closer and harder to remove.(1) /6
Answers to Questions 5-7
5. Rb, Cs, or Fr is more reactive (1)
There is not one that is less reactive (1)
6. Litmus tested for hydroxide (1)
A flaming splint tested for hydrogen gas (1)
7. The K beaker did not react because the
hydrogen was already used up (1)
This slide: /5
Total: /20
For more lessons, visit
www.chalkbored.com
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