FEINA 18 DE NOVEMBRE: RESUMIR I FER ELS DIBUIXOS DE LES TÈCNIQUES DE SEPARACIÓ DE MESCLES DEL pdf tseparacio
P1: PRESENTACIÓ DEL CRÈDIT
P2: NORMES DEL LABORATORI
1-NORMES_DE_SEGURETAT_EN_EL_LABORATORI
P3: MATERIAL DE LABORATORI
zonaClic – activitats – Utillatge i operacions al laboratori de química
5-TEORIA_Material_de_Laboratorio
Fireproof balloon
You need: 2 balloons, a candle, matches, water.
The experiment: Fill the first balloon with air and hold it over a lit candle to demonstrate to the kids that the flame will cause it to burst. Then fill the second balloon with tap water, light the candle and hold the balloon over it once again. You’ll see that in this case the balloon can withstand the heat of the flame.
Explanation: The water in the balloon absorbs the heat given out by the candle, so the material of the balloon itself doesn’t burn and then burst.
Colourful cabbage
You need: 4 glasses with water in them, food colouring, some cabbage leaves.
The experiment: Add different coloured food colouring to each glass of water, then place a single cabbage leaf in them. Leave them overnight. In the morning the leaves will have changed colour.
Explanation: Because plants absorb water, their leaves also absorb the colour of that water. This is known as the capillary effect, whereby the water will pass into the tiniest tubules of the plant. This happens with flowers, grass and even trees.
Crystallised candy
You need: 2 glasses of water, 5 glasses of sugar, small wooden kebab sticks, some thick paper, some clear glasses, a saucepan, food colouring.
The experiment: Make some sugar syrup by adding a couple of teaspoons of ordinary sugar to a quarter glass of water. Sprinkle a piece of paper with some sugar. Dip the kebab sticks in the mixture, stirring them so that pieces of sugar start to stick to them. Make sure the mixture is spread evenly along the stick, then lay them out on the paper.
Leave the sticks to dry out overnight. In the morning, dissolve five glasses of sugar in two glasses of water in a heated saucepan. Leave the resulting syrup to cool down for 15 minutes, although not for too long as otherwise the crystals won’t form. Then pour it into some empty jars and add food colouring in different colours. Place the now-ready kebab sticks in the jars, but make sure they touch neither walls or bottom – use a clothes peg to do this.
Now wait and observe what happens.
Explanation: The solubility of the syrup-water declines as its temperature falls, which produces a sediment of sugar grains on the sticks.
SABEM EL QUE MENGEM ?
Llegim les etiquetes dels productes que consumim? En parlem amb Claudi Mans, químic especialista en l’anàlisi d’etiquetes.
LABORATORI: DISSECCIÓ D’UN PEIX OSSI, dv 18 de maig
www.iesabastos.org/archivos/daniel_tomas/laboratorio/Pez/pez.html