Hand warmers and cool packs

What type of reaction occurs in hand warmers?

• Exothermic
• Endothermic

In disposable warmers what chemical is oxidised?

• Chromium
• Iron
• Potassium
• Lead

Which salt is often used in re-usable handwarmers?

• sodium chloride
• ammonium nitrate
• sodium ethanoate
• sodium nitrate

The salt Sodium Ethanoate is used in re-usable warmers. A supersaturated solution is prepared of the salt. What does this mean?

• Dissolve as much salt in water as possible
• Dissolved as much salt in acid as possible

How does the metal disc work in a re-usable handwarmer

• Starts endothermic change
• Small metal particles 'seed' the crystallisation
• Metal heats up
• Disc cools down

How do you re-use the warmer?

• Boil it - to re-dissolve crystals
• Boil it - to heat up the metal disc
• Put it in the freezer

What chemical reaction takes place in a self-heating can?

• Calcium + water --> watery calcium
• sodium oxide + water --> sodium hydroxide
• calcium oxide + water --> calcium hydroxide

Why are cold packs used in sports injuries?

• To cool the blood
• To slow the heart
• To reduce swelling and numb pain

What chemicals are used in the cold pack?

• ammonium nitrate + water
• potassium nitrate + water
• iron sulphate + water

Can instant cold packs be re-used again?

• NO
• YES
• MAYBE