Simply put - you observe them. They look very different.
The best way to learn is by doing test-tube tests in the lab and comparing the way they look.
Gelatinous ppt: This looks exactly as the name suggests - like jelly.
Adding one reagent to a test tube to a depth of about 1.5cm, then tilting the test tube at an angle of about 45° and carefully, dropwise, sliding down the second reagent usually allows a delicate, thin film to appear which can support the second reagent without it mixing with the first reagent. shaking the test tube makes the reagents mix and a jelly like ppt forms.
Alternatively, quickly squirting a small amount of the second reagent into the first causes a jelly like “swirl” of ppt. (Take care not to add too much since, depending on the reaction, some precipitates redissolve in excess sodium hydroxide.)
Example: Aluminium sulfate + ammonium hydroxide
N.B. If using NaOH, add the NaOH slowly to see the gelatinous ppt which redissolves in excess NaOH. A common mistake is to add too much NaOH too quickly and miss the formation of the ppt altogether.
White ppt: This usually looks like a powder and, depending on the concentrations and nature of the ppt, may appear as a milkiness in the solution (such as bubbling CO2 through Ca(OH)2 solution (= lime water) OR you may get a powdery deposit which settles to the bottom of the test tube leaving a clear solution above it. Occasionally, you may get fine crystals being produced such as when you add sodium sulfate to calcium chloride solution.
CAUTION: Most reactions are instantaneous, but not all are. Record your observations then save the test tube for several minutes before checking again. SOmetimes nothing happens immediately (such as the last example, above) but a ppt may form later.
NOTE You are correct to specify “white” ppt. When it comes to describing solutions a common mistake is to use “Clear” instead of “colourless” since white ppts produce colourless solutions. However a blue solution may be “clear” as may a red or green solution. “Clear” only means that the solution is transparent and says nothing about its colour.
Simply put - you observe them. They look very different.
The best way to learn is by doing test-tube tests in the lab and comparing the way they look.
Gelatinous ppt: This looks exactly as the name suggests - like jelly.
Adding one reagent to a test tube to a depth of about 1.5cm, then tilting the test tube at an angle of about 45° and carefully, dropwise, sliding down the second reagent usually allows a delicate, thin film to appear which can support the second reagent without it mixing with the first reagent. shaking the test tube makes the reagents mix and a jelly like ppt forms.
Alternatively, quickly squirting a small amount of the second reagent into the first causes a jelly like “swirl” of ppt. (Take care not to add too much since, depending on the reaction, some precipitates redissolve in excess sodium hydroxide.)
Example: Aluminium sulfate + ammonium hydroxide
N.B. If using NaOH, add the NaOH slowly to see the gelatinous ppt which redissolves in excess NaOH. A common mistake is to add too much NaOH too quickly and miss the formation of the ppt altogether.
White ppt: This usually looks like a powder and, depending on the concentrations and nature of the ppt, may appear as a milkiness in the solution (such as bubbling CO2 through Ca(OH)2 solution (= lime water) OR you may get a powdery deposit which settles to the bottom of the test tube leaving a clear solution above it. Occasionally, you may get fine crystals being produced such as when you add sodium sulfate to calcium chloride solution.
CAUTION: Most reactions are instantaneous, but not all are. Record your observations then save the test tube for several minutes before checking again. SOmetimes nothing happens immediately (such as the last example, above) but a ppt may form later.
NOTE You are correct to specify “white” ppt. When it comes to describing solutions a common mistake is to use “Clear” instead of “colourless” since white ppts produce colourless solutions. However a blue solution may be “clear” as may a red or green solution. “Clear” only means that the solution is transparent and says nothing about its colour.
To change a saturated solution to an unsaturated solution:
To change a saturated solution to an unsaturated solution:
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Simply put - you observe them. They look very different.
The best way to learn is by doing test-tube tests in the lab and comparing the way they look.
Gelatinous ppt: This looks exactly as the name suggests - like jelly.
Adding one reagent to a test tube to a depth of about 1.5cm, then tilting the test tube at an angle of about 45° and carefully, dropwise, sliding down the second reagent usually allows a delicate, thin film to appear which can support the second reagent without it mixing with the first reagent. shaking the test tube makes the reagents mix and a jelly like ppt forms.
Alternatively, quickly squirting a small amount of the second reagent into the first causes a jelly like “swirl” of ppt. (Take care not to add too much since, depending on the reaction, some precipitates redissolve in excess sodium hydroxide.)
Example: Aluminium sulfate + ammonium hydroxide
N.B. If using NaOH, add the NaOH slowly to see the gelatinous ppt which redissolves in excess NaOH. A common mistake is to add too much NaOH too quickly and miss the formation of the ppt altogether.
White ppt: This usually looks like a powder and, depending on the concentrations and nature of the ppt, may appear as a milkiness in the solution (such as bubbling CO2 through Ca(OH)2 solution (= lime water) OR you may get a powdery deposit which settles to the bottom of the test tube leaving a clear solution above it. Occasionally, you may get fine crystals being produced such as when you add sodium sulfate to calcium chloride solution.
CAUTION: Most reactions are instantaneous, but not all are. Record your observations then save the test tube for several minutes before checking again. SOmetimes nothing happens immediately (such as the last example, above) but a ppt may form later.
NOTE You are correct to specify “white” ppt. When it comes to describing solutions a common mistake is to use “Clear” instead of “colourless” since white ppts produce colourless solutions. However a blue solution may be “clear” as may a red or green solution. “Clear” only means that the solution is transparent and says nothing about its colour.
Simply put - you observe them. They look very different.
The best way to learn is by doing test-tube tests in the lab and comparing the way they look.
Gelatinous ppt: This looks exactly as the name suggests - like jelly.
Adding one reagent to a test tube to a depth of about 1.5cm, then tilting the test tube at an angle of about 45° and carefully, dropwise, sliding down the second reagent usually allows a delicate, thin film to appear which can support the second reagent without it mixing with the first reagent. shaking the test tube makes the reagents mix and a jelly like ppt forms.
Alternatively, quickly squirting a small amount of the second reagent into the first causes a jelly like “swirl” of ppt. (Take care not to add too much since, depending on the reaction, some precipitates redissolve in excess sodium hydroxide.)
Example: Aluminium sulfate + ammonium hydroxide
N.B. If using NaOH, add the NaOH slowly to see the gelatinous ppt which redissolves in excess NaOH. A common mistake is to add too much NaOH too quickly and miss the formation of the ppt altogether.
White ppt: This usually looks like a powder and, depending on the concentrations and nature of the ppt, may appear as a milkiness in the solution (such as bubbling CO2 through Ca(OH)2 solution (= lime water) OR you may get a powdery deposit which settles to the bottom of the test tube leaving a clear solution above it. Occasionally, you may get fine crystals being produced such as when you add sodium sulfate to calcium chloride solution.
CAUTION: Most reactions are instantaneous, but not all are. Record your observations then save the test tube for several minutes before checking again. SOmetimes nothing happens immediately (such as the last example, above) but a ppt may form later.
NOTE You are correct to specify “white” ppt. When it comes to describing solutions a common mistake is to use “Clear” instead of “colourless” since white ppts produce colourless solutions. However a blue solution may be “clear” as may a red or green solution. “Clear” only means that the solution is transparent and says nothing about its colour.
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