Temperature effects on solubility
To investigate the dissolution of substances and introduce the concept of solubility.
Cosa imparano gli studenti
La scienza alla base di questo esperimento
How and why does a solute dissolve in water? Have you ever noticed that hot water cleans better? This experiment examines what happens to a number of substances when they are mixed with water, and what effect temperature has on dissolution.
When a crystalline salt is placed in water, the water molecules surround the ions and weaken the bonds holding the ions together in the solid and allow ions to move into solution.
The solubility of a substance determines the tendency of its particles to go into solution and is defined as the mass of solute which will saturate 100 g of solvent. When the solvent is water, 100 g is often replaced by 100 ml but this is not recommended as good practice.
Substances dissolve to a point where the solution is saturated and no more solid can dissolve.
In some cases, the solubility may be very high and a large amount of solid will dissolve before the solution becomes saturated.
Solubility of various solutes in water covers a very wide range.
Some highly soluble salts dissolve very easily, as is the case with potassium nitrate, copper sulphate and sucrose.
Other salts don’t seem to dissolve at all (1×10–15 g in 1 kg water), whatever the temperature. The description "very soluble" generally means sufficiently soluble to form 0.1 to 1.0 molar aqueous solutions. Salts which are less soluble in water than this at room temperature are called slightly soluble salts.
Attrezzatura utilizzata
- Provette — 1473,60
- Portaprovette — 1680.06
- Portaprovette — 5423.30
- Spatula double end — 5460.34
- Spirit burner — 5414.10
- Tripod stand — 5533.10
- Iron stand — 5404.51
- Wire gauze — 5534.25
- Beaker 250 ml — 1118.35
- Thermometer — 2245.15
- Glass rod — 1444.10
Sostanze chimiche e reagenti
- Calcium carbonate — R:37/38-41 S:26-36/37/39
- Solfato di rame — R:22-35/38-50/53 S:22-60-61
- Cloruro di sodio
- Sucrose
- Acqua distillata
Note sulla sicurezza
- Prestare attenzione durante l'uso del bruciatore e degli oggetti in vetro caldi.
Domande per gli studenti
- Which substance has dissolved?
- What does the water do to the substances?
- What happens on increasing the temperature?
- Why does calcium carbonate not dissolve?
Cosa aspettarsi
<p>Sodium Chloride dissolves Copper Sulphate dissolves Sucrose dissolves.</p><p>Water molecules surround salt ions weakening their attraction.</p><p>As water is a polar molecule, it tends to orientate itself around the ions according to the sign.</p><p>At the higher temperature, sodium chloride and copper Sulphate and sucrose dissolve faster. Calcium Carbonate does not dissolve appreciably yet.</p><p>At higher temperatures, there is faster movement of the particles in the solution and therefore the dissolution is easier.</p><p>Calcium carbonate is a very low soluble salt.</p>
Smaltimento
Smaltire le soluzioni nel contenitore per i rifiuti liquidi.
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