Dalton's initial models with water
According to Dalton's initial atoms key, which element is represented by a solid black circle • ?
Carbon
True or False: Boiling water and electrolysis of water both produce hydrogen gas.
False
What is the main purpose of an MRE?
To give people a portable meal that can be eaten anywhere
Which two metals listed in the MRE heater ingredients react with salt to produce heat when water is added?
Magnesium and iron
what does the term "atom" mean?
uncuttable
Dalton used symbols instead of colors for elements. Give one good reason why symbols are helpful when drawing models of atoms or molecules.
To differentiate them.
Say one main difference between boiling water and electrolysis of water (short sentence).
Boiling changes liquid water to water vapor (physical), electrolysis breaks water into different substances (chemical).
Name three situations where MREs can be used.
Outdoor adventures, military missions, emergencies
What gas is released by the MRE heater during the reaction?
Steam and hydrogen gas
Say the full name for the atom symbol: Na.
Sodium
Dalton's model suggests that samples of pure Sodium (Na) and pure Chlorine (Cl) are mainly made of what?
atoms
What supplies the energy in the electrolysis process described in the exam?
Energy from a battery (electrical energy)
Which is a shared ingredient between MRE heaters and hand warmers?
Iron and salt
The MRE heater reaction is classified as exothermic or endothermic? Explain what that term means in one sentence.
Exothermic — it releases heat into the environment.
What is the symbol used to represent Magnesium?
Mg
Name the two gases produced when water is broken down in Dalton's Atomic Models table after adding energy from a battery.
Hydrogen and oxygen
When water undergoes electrolysis, what happens to the chemical bonds in water molecules?
Chemical bonds between hydrogen and oxygen atoms are broken and new bonds are not formed to make the same water molecules (atoms rearrange into H2 and O2).
Why are MREs not recommended for long-term daily use?
They contain high levels of sodium and preservatives
List 3 ingredients named in the passage that are in the MRE heater.
magnesium, iron salt
How many elements have scientists discovered so far?
118
Draw (describe in words) a simple particle model showing one water molecule
H20 it has two atoms of hydrogen and one atom of oxygen
Explain why boiling water is a physical change and electrolysis is a chemical change. Use one example sentence for each.
Boiling is physical because the substance (H2O) stays as H2O, only its state changes; electrolysis is chemical because new substances (H2 and O2) form.
Give two safety precautions someone should take when handling an MRE heater.
Example safety precautions: avoid inhaling powdered components; keep heater pouch sealed until ready; follow manufacturer instructions and avoid ingesting heater contents.
Describe, in 2–3 sentences, how water causes the MRE heater to produce heat (use the words: react, exothermic, steam, hydrogen if possible).
Water activates the powdered metals and salt, enabling oxidation reactions that release energy as heat (exothermic), producing steam and hydrogen gas as by-products.
Give two examples of compounds
Iron oxide, sodium chloride