Conservation Of Mass D. Crowley, 2007. Conservation Of Mass To be able to explain why mass is...
-
Upload
stewart-barrett -
Category
Documents
-
view
214 -
download
0
Transcript of Conservation Of Mass D. Crowley, 2007. Conservation Of Mass To be able to explain why mass is...
Conservation Of MassConservation Of Mass
D. Crowley, 2007D. Crowley, 2007
Conservation Of MassConservation Of Mass
To be able to explain why mass is conserved when substances dissolve
To be able to explain why mass is conserved when substances dissolve
Wednesday, April 19, 2023
DissolvingDissolving
See if you can identify as many facts about dissolving as you can…
What do you think will happen to the mass of water if salt is added to it?
Using these facts, write a small paragraph in your book why salt dissolves
See if you can identify as many facts about dissolving as you can…
What do you think will happen to the mass of water if salt is added to it?
Using these facts, write a small paragraph in your book why salt dissolves
Salt DissolvingSalt Dissolving Some substances are soluble meaning they dissolve They are able to mix completely with a liquid, forming a
transparent mixture
Salt (the solute) dissolves in water (the solvent), and its particles become completely mixed in our newly formed solution.
But the mass stays the same - we do not loose any salt or water particles, they are just mixed up, which is why they become difficult to see
Some substances are soluble meaning they dissolve They are able to mix completely with a liquid, forming a
transparent mixture
Salt (the solute) dissolves in water (the solvent), and its particles become completely mixed in our newly formed solution.
But the mass stays the same - we do not loose any salt or water particles, they are just mixed up, which is why they become difficult to see
Solute Solvent Solution
ParticlesParticles
Look at the particle model for the soluble sugar: -Look at the particle model for the soluble sugar: -
Sugar, added to the water
Water
ParticlesParticles
Look at the particle model for the soluble sugar: -Look at the particle model for the soluble sugar: -
Water
Sugar, added to the water
Sugar and water solution
ParticlesParticles
DemonstrationDemonstration What will happen to the rice and peas when they are
placed in water?
Can you identify what will happen in our particle model?
What can you say about the mass of the water and the peas?
What will happen to the rice and peas when they are placed in water?
Can you identify what will happen in our particle model?
What can you say about the mass of the water and the peas?
MassMass Remember - the mass always stays the same - even if
the solute dissolves
Both substances are still there, however the solute may have mixed with the solvent forming a solution
Remember - the mass always stays the same - even if the solute dissolves
Both substances are still there, however the solute may have mixed with the solvent forming a solution
Getting Salt BackGetting Salt Back
Imagine you added some salt to water
The salt would dissolve in the water
How could you get your salt back?
Imagine you added some salt to water
The salt would dissolve in the water
How could you get your salt back?
FiltrationFiltration Filtration is great at seperating insoluble solids (like our
pea) from the liquid It does this by creating a barrier which the larger
insoluble particles cannot pass
E.g. the large peas cannot pass through the filter (like using a sieve at home)
Why is this process no use in seperating salt from water (something which has dissolved)?
Filtration is great at seperating insoluble solids (like our pea) from the liquid
It does this by creating a barrier which the larger insoluble particles cannot pass
E.g. the large peas cannot pass through the filter (like using a sieve at home)
Why is this process no use in seperating salt from water (something which has dissolved)?
Large peas do not dissolve (their particles remain
together), so can be easily filtered using a sieve
FiltrationFiltration When something dissolves, the solute particles become
spread throughout the solvent
Because the particles are so spread out, a barrier will not stop them (they pass straight through)
This is why filtration is no use
Instead we must use evaporation – boiling off the water and leaving the salt behind
You task it to dissolve 1 gram of salt in water and via evaporation get the salt back – most accurate wins!
When something dissolves, the solute particles become spread throughout the solvent
Because the particles are so spread out, a barrier will not stop them (they pass straight through)
This is why filtration is no use
Instead we must use evaporation – boiling off the water and leaving the salt behind
You task it to dissolve 1 gram of salt in water and via evaporation get the salt back – most accurate wins!
DissolvingDissolving
Remember, when something dissolves its particles spread throughout the solvent, forming a solution
This is a lot like diffusion, where the particles (net) went from an area of high to low concentration
How could you speed up dissolving?
Remember, when something dissolves its particles spread throughout the solvent, forming a solution
This is a lot like diffusion, where the particles (net) went from an area of high to low concentration
How could you speed up dissolving?
Heat!Heat! The particles diffused quicker when they were heated -
more heat gives them more energy, so they move quicker
This can be applied to diffusion - heat the particles and they will diffuse quicker
Try it yourself - get an equal quantity of water and sugar for two cups
With one cup, use tap water With the other use boiling water Add the sugar, and see which dissolves quicker!
H/W - explain this to someone at home!
The particles diffused quicker when they were heated - more heat gives them more energy, so they move quicker
This can be applied to diffusion - heat the particles and they will diffuse quicker
Try it yourself - get an equal quantity of water and sugar for two cups
With one cup, use tap water With the other use boiling water Add the sugar, and see which dissolves quicker!
H/W - explain this to someone at home!