C7.2 - Using energy transfers from reactions Flashcards
What can chemical hand and body warmers be?
Chemical:
1. Hand
2. Body
warmers can be very useful
Chemical hand and body warmers can be very useful.
What do these products use to warm you up?
These products use exothermic reactions to warm you up
What can people do with hand warmers?
People can take hand warmers to places they know will get very cold
People can take hand warmers to places they know will get very cold.
Example
For example, spectators at outdoor sporting events in winter can warm their hands
What do people usually use chemical body warmers to do?
People usually use chemical body warmers to help ease:
- Aches
- Pains
What can some hand warmers be?
Some hand warmers can only be used once
Some hand warmers can only be used once.
What do these hand warmers make use of?
These hand warmers make use of the energy transferred to the surroundings in the oxidation of iron
Some hand warmers can only be used once.
These hand warmers make use of the energy transferred to the surroundings in the oxidation of iron.
What happens to iron, in an exothermic reaction?
In an exothermic reaction, iron turns into hydrated iron(III) oxide
Some hand warmers can only be used once.
These hand warmers make use of the energy transferred to the surroundings in the oxidation of iron.
Iron turns into hydrated iron(III) oxide in an exothermic reaction.
What is the reaction similar to?
The reaction is similar to rusting
Some hand warmers can only be used once.
These hand warmers make use of the energy transferred to the surroundings in the oxidation of iron.
Iron turns into hydrated iron(III) oxide in an exothermic reaction.
What is used as a catalyst?
Sodium chloride (common salt) is used as a catalyst
Some hand warmers can only be used once.
These hand warmers make use of the energy transferred to the surroundings in the oxidation of iron.
Sodium chloride (common salt) is used as a catalyst.
What is this type of hand warmer?
This type of hand warmer is disposable
Some hand warmers can only be used once.
What can other hand warmers be?
Other hand warmers can be used many times
Some hand warmers can only be used once.
Other hand warmers can be used many times.
What are these based on?
These hand warmers are based on the formation of crystals from solutions of a salt
Some hand warmers can only be used once.
Other hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
What is the salt used often?
The salt used is often sodium ethanoate
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
The salt used is often sodium ethanoate.
A supersaturated solution is prepared by doing what?
A supersaturated solution is prepared by dissolving as much of the salt as possible in hot water
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
What is used to start the exothermic change?
A small metal disk in the plastic pack is used to start the exothermic change
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
A small metal disk in the plastic pack is used to start the exothermic change.
What happens when you press the small metal disk?
When you press the small metal disk a few times, small particles of metal are scraped off
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
A small metal disk in the plastic pack is used to start the exothermic change.
When you press the small metal disk a few times, small particles of metal are scraped off.
These ‘seed’ (or start off) the crystallisation.
What do the crystals do?
The crystals spread throughout the solution, transferring energy to the surroundings in an exothermic change
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
How do you reuse the warmer?
To reuse the warmer, you simply put the solid pack into boiling water to re-dissolve the crystals
What happens during the recrystallization of sodium ethanoate in a hand warmer?
During the recrystallization of sodium ethanoate in a hand warmer, energy is transferred from the reaction system to the surroundings
Where are exothermic reactions also used, other than in chemical hand and body warmers?
Other than in chemical hand and body warmers, exothermic reactions are also used in self-heating cans that makes drinks like hot coffee without any external heating device, like a kettle
Other than in chemical hand and body warmers, exothermic reactions are also used in self-heating cans that makes drinks like hot coffee without any external heating device (like a kettle).
What is the reaction used to transfer energy to the food or drink usually?
The reaction used to transfer energy to the:
1. Food
Or,
2. Drink
is usually:
Calcium oxide + Water —> Calcium hydroxide
How do self-heating cans work?
Self-heating cans work by you pressing a button in the base of the can
What did development of the self-heating coffee can do?
Development of the self-heating coffee can:
- Took years
- Cost millions of pounds
Development of the self-heating coffee can took years and cost millions of pounds.
Even then, what was over a third of the can?
Even then, over a third of the can was taken up with the reactants needed to transfer enough energy to the coffee
Development of the self-heating coffee can took years and cost millions of pounds.
Even then, over a third of the can was taken up with the reactants needed to transfer enough energy to the coffee.
Also, what happened in some early versions?
Also, in some early versions, the temperature of the coffee did not rise high enough in cold conditions
Development of the self-heating can in the USA took how many years?
Development of the self-heating can in the USA took about 10 years
What can be used to cool things down?
Endothermic processes can be used to cool things down
Endothermic processes can be used to cool things down.
Example
For example, chemical cold packs usually contain:
1. Ammonium nitrate
2. Water
,sometimes present in a gel
Endothermic processes can be used to cool things down.
For example, chemical cold packs usually contain ammonium nitrate and water, sometimes present in a gel
What happens when ammonium nitrate dissolves?
When ammonium nitrate dissolves, it absorbs energy from its surroundings
Chemical cold packs usually contain ammonium nitrate and water.
When ammonium nitrate dissolves, it absorbs energy from its surroundings, making them colder.
Why are chemical cold packs used?
Chemical cold packs are used as emergency treatment for sports injuries
Chemical cold packs usually contain ammonium nitrate and water.
How are the ammonium nitrate and water kept in the chemical cold pack?
The:
1. Ammonium nitrate
2. Water
are kept separate in the pack
Chemical cold packs usually contain ammonium nitrate and water.
The ammonium nitrate and water (sometimes present in a gel) are kept separate in the pack.
What happens when squeezed or struck?
When: 1. Squeezed Or, 2. Struck ,the bag inside the water pack breaks
How often can instant cold packs be used?
Instant cold packs can only be used once
Instant cold packs can only be used once, but when are they ideal?
Instant cold packs can only be used once, but they are ideal where there is no ice available to treat a:
1. A knock
Or,
2. Strain
Instant cold packs can only be used once, but they are ideal where there is no ice available to treat a knock or strain.
Where are instant cold packs often included?
Instant cold packs are often included in the first aid kit at venues used for:
1. Amateur sports
Or,
2. Outdoor pursuits
Endothermic processes can be used to cool things down.
For example, chemical cold packs usually contain ammonium nitrate and water.
What can the same endothermic change also be used to do?
The same endothermic change can also be used to chill cans of drinks
When can instant cold packs be applied?
Instant cold packs can be applied as soon as an injury occurs to minimise damage
Some hand warmers can only be used once.
These hand warmers make use of the energy transferred to the surroundings in the oxidation of iron.
Sodium chloride (common salt) is used as a catalyst.
This type of hand warmer is disposable.
It can be used only once, but it what?
It can be used only once, but it lasts for hours
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
The salt used is often sodium ethanoate.
A supersaturated solution is prepared by dissolving as much of the salt as possible in hot water.
The solution is then what?
The supersaturated solution is then allowed to cool
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
A small metal disk in the plastic pack is used to start the exothermic change.
When you press the small metal disk a few times, small particles of metal are scraped off.
These do what?
These: 1. 'Seed' Or, 2. Start off the crystallisation
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
A small metal disk in the plastic pack is used to start the exothermic change.
When you press the small metal disk a few times, small particles of metal are scraped off.
These ‘seed’ (or start off) the crystallisation.
The crystals spread throughout the solution, transferring energy to the surroundings in an exothermic change.
They work for how long?
They work for about 30 minutes
Some hand warmers can be used many times.
These hand warmers are based on the formation of crystals from solutions of a salt.
To reuse the warmer, you simply put the solid pack into boiling water to re-dissolve the crystals.
Once it has cooled down, the pack is what?
Once it has cooled down, the pack is ready to activate again
During the recrystallization of sodium ethanoate in a hand warmer, energy is transferred from the reaction system to the surroundings, increasing what?
During the recrystallization of sodium ethanoate in a hand warmer, energy is transferred from the reaction system to the surroundings, increasing the temperature of the surroundings, your hand
Self-heating cans work by you pressing a button in the base of the can.
This does what?
You pressing a button in the base of the can breaks a seal and lets the water and calcium oxide mix
Self-heating cans work by you pressing a button in the base of the can.
You pressing a button in the base of the can breaks a seal and lets the water and calcium oxide mix.
Then what?
Then the exothermic reaction can begin
Endothermic processes can be used to cool things down.
For example, chemical cold packs usually contain ammonium nitrate and water.
When ammonium nitrate dissolves, it absorbs energy from its surroundings, doing what?
When ammonium nitrate dissolves, it absorbs energy from its surroundings, making them colder
Chemical cold packs usually contain ammonium nitrate and water.
When ammonium nitrate dissolves, it absorbs energy from its surroundings, making them colder.
Why are chemical cold packs used as emergency treatment for sports injuries?
Chemical cold packs are used as emergency treatment for sports injuries, because the decrease in temperature:
- Reduces swelling
- Numbs pain
Chemical cold packs usually contain ammonium nitrate and water.
The ammonium nitrate and water (sometimes present in a gel) are kept separate in the pack.
When squeezed, or struck, the bag inside the water pack breaks, releasing what?
When: 1. Squeezed Or, 2. Struck ,the bag inside the water pack breaks, releasing ammonium nitrate
Chemical cold packs usually contain ammonium nitrate and water.
The ammonium nitrate and water (sometimes present in a gel) are kept separate in the pack.
When squeezed, or struck, the bag inside the water pack breaks, releasing ammonium nitrate.
The instant cold packs work for how long?
The instant cold packs work for about 20 minutes
