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Chemistry Core Practicals - Coggle Diagram
Chemistry Core Practicals
Chromatography
:!:it is used to separate mixtures of soluble substances and provide information on the possible identity of the substances
Equipment:
pencil, chromatography paper, pipette, ink, beaker, solvent, ruler, eye protection
The Science:
the paper id the stationary phase and the solvent is the mobile phase. Each substance has different attractions to the stationary phase and the mobile phase causing the mixture to separate. The substance that is most attracted to the solvent/ lack of attraction to the paper will travel the furthest.
Method:
1.Draw a pencil line with a ruler on the paper. 2.Use a pipette to drop some ink on the pencil line. 3.Place solvent in the beaker and set paper in the solvent but not touching the ink.
4.Allow solvent to rise up paper, causing the mixture to separate.
5.Leave to dry out of the beaker then measure and record your results
Control Variable and Risk Factor:
you have to keep the temperature of the room and the solvent volume the same. Materials found in the lab can be corrosive, flammable, toxic or explosion hazard. Therefore you have to wear eye protection and gloves so you don't get eye damage or skin burns.
Neutralisation
:!:to investigate the change in pH when adding calcium powdered hydroxide to a fixed volume of dilute hydrochloride acid
Equipment:
measuring cylinder, beaker, glass rod, spatula, universal indicator paper
The science:
when an acid and base is mixed a chemical reaction happens called neutralisation and the pH changes to 7.
Method:
1.Use a measuring cylinder to add dilute hydrochloric acid and put in a beaker. 2.Use the glass rod to add a drop of the acid onto the universal indicator on a white tile and wait 30 seconds then match and record the colour of the pH level. 3.Add a level spatula of calcium hydroxide powder to the beaker. 4.Stir then estimate and record the pH level (as in step 2). 5.Repeat steps 3 and 4 until there are no change in pH.
Control Variable and Risk Factor:
you have to keep the enzyme concentration and volume and the pH table reference the same. Hydrochloric acid is corrosive so use dilute acid, calcium hydroxide powder can cause skin and eye eye irritation so wear eye protection and gloves and it can also cause respiratory irritation so avoid making dust.
Preparing a Salt
:!:to prepare a dry pure sample of a soluble salt
Equipment:
eye protection, beaker, measuring cylinder, spatula, glass rod, Bunsen burner, tripod, gauze, filter funnel, filter paper, evaporating basin.
The Science:
a salt is produced when an acid reacts with a metal, alkali, base or metal carbonate. The salt depends on the acid used for example: sulfuric acid forms sulphate, hydrochloric acid forms chloride and nitric acid forms nitrate.
Method:
1.Measure 50cm^3 of dilute sulphuric acid and pour in a beaker.
2.Place beaker on tripod and gauze and warm gently to speed up reaction.
3.Add copper oxide in small amounts and stir. 4.Stop adding when some unreacted copper oxide remains.
5.Filter the mixture add heat the beaker using a water bath until crystals begin to form. 6.Pour it into an evapourating basin and leave in warm place until crystals have formed. 7.Scrape the crystals onto filter paper and pat dry.
Control Variable and Risk Factor:
you have to keep the same volume of solution, same mass of copper oxide, same temperature of reaction and same particle size of copper. The acid can be corrosive if concentrated and cause skin damage so use dilute acid, the boiling water bath can cause skin burns so ensure it is stable and hot copper can spit out during crystallisation causing skin or eye damage so wear eye protection and avoid standing over apparatus.
Electrolysis
:!:to investigate what products are produced when different aqueous solutions are electrolysed
Equipment:
eye protection, solutions of potassium, bromide, calcium nitrate, copper nitrate and copper chloride, graphite electrodes, electrical circuit, electrolysis cell, two small text tubes
The Science:
aqueous solutions of iconic compounds conduct electricity because ions are free to move and graphite is inert. The positive ions move to the negative electrode (cations to cathode) and either hydrogen or the metal in the ionic compound is formed here. The negative ions move to the positive electrodes (anions to anode) and either oxygen or a halgen is formed here.
Method:
1.Set up apparatus.
2.Pour one of the solutions (electrolytes) into the cell.
3.Turn on the d.c supply.
4.Collect any gases produced in the test tubes and note observations at the electrodes.
Control Variables and Risk Factors:
you have to keep the aluminium electrodes, electrode size, power supply, electrolyte amount, concentration and temperature the same. Copper sulphate solution can cause serious skin and eye irritation so wear gloves and glasses and propanone is highly flammable so keep away from flames.
