How to lower the intensity of the Bunsen burner

Adjusting the Flame. Use the needle valve to control the flame's size. The needle valve on the bottom of the Bunsen burner adjusts the gas flow rate, which determines the height of the flame. More gas will create a larger flame, and less gas gives you a smaller flame.

Explanation:

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you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

it's all four options.