2.6 Describe the reactions of these elements with water and understand that the reactions provide a basis for their recognition as a family of elements

By "these elements", they mean group 1 metals.

Lithium (Li), Sodium (Na) and Potassium (K) all react vigorously with water. The rest further down the group...well...it's probably not safe to experiment with those in a lab (or anywhere, really...)

Lithium

• Floats
• Fizzes
• Solid eventually disappears
• Produces some heat but doesn't melt

Sodium

• Floats
• Heat given off, causing it to melt into a ball
• Gradually disappears
• Sometimes a white trail of sodium hydroxide can be seen, but it usually ends up dissolved in the water
• Moves around (due to hydrogen given off)
• If it gets stuck on the side of the container, it will burn with an orange flame.

Potassium

• Burns with a lilac flame
• Reacts similarly to sodium but quicker
• Gives off heat, causing it to melt into a ball

As you go down the group, the reactions become more vigorous. There's plenty of videos on YouTube :) (even of the super reactive ones...they're pretty impressive)