Science Bell Ringers for Grades 9–12
This page collects every science bell ringer we have posted for grades 9–12: 2 bell ringers so far, newest first, with a new one added each school day. Each is a 3–5 minute warm-up for high school students covering predict-and-explain questions and short problems from life, earth and physical science. The answer and teacher notes sit in the collapsed box under each prompt, so you can project the page without giving anything away.
Balancing the equation for burning methane
Natural gas is mostly methane (CH4). When it burns completely, it reacts with oxygen to make carbon dioxide and water. Balance the equation, then prove it is balanced by counting atoms on each side.
__ CH4 + __ O2 → __ CO2 + __ H2O
Answer and teacher notes
CH4 + 2 O2 → CO2 + 2 H2O
Atom count: carbon 1 = 1. Hydrogen 4 = 2 × 2 = 4. Oxygen 2 × 2 = 4 on the left; 2 (in CO2) + 2 × 1 (in water) = 4 on the right. Tip: balance C and H first, then O last, since oxygen shows up in both products. Students who change subscripts (writing H4O) have changed the substance, not balanced it.
Source: U.S. Energy Information Administration: Natural Gas Explained
The physics of a 66-kilometer-per-second meteor
Orionid meteors enter Earth's atmosphere at about 66 kilometers per second. (a) How far does one travel in 3 seconds? (b) The grains are about the size of sand. Why do they glow and burn up instead of reaching the ground?
Answer and teacher notes
(a) 66 km/s × 3 s = 198 km.
(b) At that speed the grain slams into the air in front of it. That air is squeezed and heated so fast that the grain heats up and vaporizes, which is the streak of light we see. Students often say "friction"; that is part of it, but compressed, superheated air does most of the work.
Source: NASA: Orionids Meteor Shower
Free to use. Copy, print, project or adapt any of these for your students. If you share them online, please credit Daily Bell Ringers with a link. Not for resale. License: CC BY-NC 4.0.
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Want more? See our ready-made list of science bell ringers and how to run bell ringers in high school, or make a custom one with the free bell ringer generator.