Any ideas? (1 Viewer)

[+GriM ReApeR+]

"At home, you are required to find 3 common everyday substances which can be used as indicators..."

I know that I can use a red cabbage/flower indicator, but are there any others? More unique ones?

Thanks

 

[Xayma]

Rose petals, and there are a number of flowers which change colour depending on soil aciditity.

 

[danif]

black tea is also an indicator (apparently)

 

[grimreaper]

red wine is also an indicator, and yes, tea is an indicator as well

 

[CM_Tutor]

Hydrangeas are an example of a flower that changes colour with soil pH - in fact, you can buy 'hydrangea pinking compound' and 'hydrangea bluing compound', which are simple an acid and a base.

 

[Xayma]

Speaking of the bluing compounds with soil acidity, will lime only neutralise the acidity of the soil and not make it more basic (as in not raise it above 7) since its a Carbonate?

 

[CM_Tutor]

Isn't lime calcium oxide, CaO, rather than CaCO₃, which is limestone?

 

[Xayma]

It is to, so it forms a basic salt, makes sense. My Engineering studies teacher told me that they were the same thing when we were doing the composition of concrete *rants

 

[CM_Tutor]

It is usual practice not to call oxides salts...

As for concrete, remember that calcium oxide is basic, and carbon dioxide is acidic, so lime slowly absorbs CO₂ from air becoming limestone:

CaO_(s) + CO_{2 (g)} ---> CaCO_{3 (s)}

It is for this reason that most metal oxides only have short shelf-life, as they are slowly converted to carbonates in air. This may mean that are considered interchangeable at times.

Remember, also, that non-scientists tend to be a bit reckless with chemical concepts, and engineers are a prime example of this problem!

 

[xiao1985]

oh yea... i heard from somewhere that they add limes to increase the pH so that the soil is suitable for some plant's growth...

hehe, yea... engineerin sucks... all my fwnds either dun talk abt it, or said it sucked bit time... (well, apparently, they ain't good programmers, n they need to do software... n i was like, AHAHAHAH each time... =(... )

hey, cm_tutor, are you in that school tutorin program??i mean, u must be ^^seein u r like so good and all...

 

[CM_Tutor]

Originally posted by xiao1985
hey, cm_tutor, are you in that school tutorin program??i mean, u must be ^^seein u r like so good and all...

If you mean the one at USyd, then no.

 

[Xayma]

Originally posted by xiao1985
oh yea... i heard from somewhere that they add limes to increase the pH so that the soil is suitable for some plant's growth..

It is also used on salinity affected soils, but I dont know what effect it would have there, unless some of the compounds that are brought up with the ground water are non-metal oxides.

 

[kalinda]

you can always use cabbage which is an obvious one