Chromatography at Home

You will need:

  • Kitchen roll
  • Felt tip pens
  • Water
  • Bowl or cup
  • Scissors

What to do:

  1. Cut a long strip from one sheet of kitchen roll. It should be 2 cm or 1 inch wide.
  2. Choose one felt tip pen and draw a big dot at the bottom of your kitchen roll strip. IMPORTANT: Do not draw the dot all the way at the bottom, leave about 2 to 3 cm from the bottom to the dot.
  3. Pour some water into a bowl or cup.
  4. Place the bottom of your kitchen roll strip in the water and watch what happens. IMPORTANT: When you do this, the dot must be above the water.
  5. Repeat the method with other felt tip pens.

Background

The inks in felt tip pens are made by mixing different colouring materials, called “pigments”. We can use chromatography separate the different colours because some are soaked up the kitchen roll faster than others.

The reason is that the different pigments have different solubilities in water. The further the colour travels, the more soluble it is. Less soluble colours stay at the bottom.

You can watch a video of this experiment here:

Red Cabbage Indicator

You will need

  • 1 Sauce pan
  • 1 Chopping board
  • 1 Knife
  • 1 large glass jar
  • 4 small glass jars
  • 1 Red Cabbage
  • Vinegar, lemon juice, water and bicarbonate of soda to test

What to do

  1. Carefully chop the red cabbage leaves into small pieces on the chopping board.
  2. Put the red cabbage in a sauce pan and add water until the red cabbage leaves are completely covered.
  3. Gently boil the red cabbage for 10 to 15 minutes.
  4. After the sauce pan has cooled down, collect the water in a large jar.
  5. To better see the red cabbage water’s colour add some water to dilute it.
  6. Transfer the red cabbage water into the 4 small jars.
  7. Add a dash of vinegar to the first small jar with red cabbage juice and observe what happens.
  8. Repeat step 7 for the other substances you want to test. Each substance goes into a new small jar with red cabbage juice.
  9. What colour changes do you observe?

Background

Red cabbage juice is a pH indicator. This means it changes colour depending on if it is in an acidic, alkaline or neutral environment. In this experiment you are testing some acids (vinegar and lemon juice), some alkalis (bicarbonate of soda) and a neutral substance (water).

Which colour changes can you observe in your experiment? What colour does red cabbage indicator have in acids, bases or with neutral substances?

You can watch this experiment as a video here:

Candle Experiment

You will need

  • Candle
  • Matches or lighter
  • 3 Jars of different sizes
  • Heatproof base, for example a ceramic plate
  • Stopwatch/timer (your mobile phone will do)

What to do

  1. Put the candle on the heatproof base and light it.
  2. Put the smallest jar upside down over the candle and start the timer.
  3. Time how long it takes for the candle to go out and record the time.
  4. Repeat steps 2 and 3 for the medium sized jar and the large jar.
  5. Record for each candle how long it burns. Under which jar does the candle burn longest?

Background

Oxygen is needed for a fire to burn. This is also true for candles. The oxygen is normally supplied by the air.

When placing a jar over the candle, the amount of oxygen for the candle is limited. The candle goes out when all oxygen in the jar is used up. The amount of oxygen depends on the size of the jar.

Under which jar does the candle burn longest? Why do you think that is?

You can watch a video of this experiment here:

Grow a Crystal

You will need

  • Short length of wool or string
  • Warm water
  • 2 Paperclips
  • 1 Plate
  • 1 Spoon
  • 2 Glass jars
  • Washing soda

What to do

  1. Fill both jars with warm water. (From the tap is fine.)
  2. Add washing soda to both jars and stir until no more washing soda dissolves.
  3. Attach a paperclip to each end of the string or wool.
  4. Place the ends of the string in the jars, so the string hangs between the jars.
  5. Place a plate between the jars to catch the drips of the solution flowing along the string or wool.
  6. Leave the jars for one to two weeks in a safe place and observe what happens.

Background

The washing soda solution slowly soaks the string or wool and flows along it. As the solution drips off some washing soda is deposited slowly forming a crystal.

Water flowing underground dissolves minerals when it seeps through rocks. The minerals are deposited when the water drips of a cave roof. A crystal is formed that hangs off the cave rood which we call “stalactite”. When the water drips to the floor it deposits minerals there forming a crystal growing up from the ground which we call “stalagmite”.

In your experiment a stalactite grows hanging from the string or wool.

You can watch a video of this experiment:

Combustion of Christmas Nuts

You will need

  • 1 Sharp knife
  • Matches
  • Heat proof surface, for example a pan or a ceramic plate
  • 1 Potato
  • 1 Peanut
  • 1 Almond
  • 1 Walnut
  • If you are allergic to nuts you can use sunflower and pumpkin seeds instead.

What to do

  1. Cut a potato into a long cylinder or a tall rectangular cube.
  2. Carefully cut a long thin strip from the peanut, almond and walnut.
  3. Stick 1 peanut strip into the top of the potato. The potato will hold the peanut while it is burning.
  4. Light the peanut strip with a match. Let it burn until it goes out.
  5. Repeat steps 3 and 4 with one almond and one walnut strip.
  6. Which nut burns longest? Which nut is easiest to light?

Background

Nuts contain oil that can be lit to create a fire. The oil and the oxygen from the air undergo a chemical change during the fire turning them into carbon dioxide gas and steam. This type of reaction producing a fire is called “combustion”.

The nut that lights fastest and burns longest contains most oil. Which nut contained most oil?

You can watch a video of the experiment here:

Vinegar and Baking Soda Bomb

Background

Vinegar is an acid and reacts with baking soda to form salt, water and carbon dioxide gas. The extremely fast formation of carbon dioxide gas will cause your zipper back bomb to explode.

You will need

  • Plastic zipper bag
  • Vinegar (any kind will do, but you will need quite a lot of it)
  • Baking soda
  • Cup, glass or mug
  • Table spoon

What to do

  1. Go outside to do this experiment.
  2. Check your zipper bag to make sure that it does NOT have any holes or rips before the experiment.
  3. Fill your glass or mug completely with vinegar
  4. Pour the vinegar from your glass or mug into the plastic zipper bag.
  5. Place the zipper bag on the ground.
  6. Add one heaped table spoon of baking soda and quickly close the bag.
  7. Quickly step away from the zipper bag and watch what happens.

You can watch this experiment here:

How to use our Mobile Devices more Sustainably

Image Credit: Yutaka Tsutano, US. CC by 2.0.

To most people mobile devices like smartphones are so much more than simple everyday objects. In personal messages, music, notes and calendars they basically contain our entire lives.

Despite the deep relationship to our smartphone, many do not hesitate to replace it with the newer model as soon as they get the chance. A report from 2016 suggests that in the UK smartphones are replaced by a newer version every two years.

Many people are not ware what the costs of this tech consumerism are. Smartphones, laptops and other consumer electronics contain up to 92 different elements and the origin of some is very problematic.

One example is the metal cobalt which is used in the lithium-ion batteries powering our devices. Cobalt normally comes from mines in African countries like the Democratic Republic of  Congo (DRC). Cobalt miners in these countries have to endure harsh working conditions with little to no safety regulations to protect them. The cobalt mines in DRC have also been linked to the use of child labour.

Other metals in mobile devices that have the same issues are gold, tantalum and tin. Gold and tantalum are used in the electric circuits while tin is contained in touch screens.

These metals, cobalt, gold, tantalum and tin, are also called ”conflict minerals”. The reason is that their trade has been linked to funding killings and violence in the DRC and other places.

In addition, the large scale mining and extraction of the metals needed to make a mobile device causes pollution and devours large amounts of energy, which in turn fuels global warming. And it does not stop there. After extraction the metals are mostly transported to China where the devices are assembled often by workers with low pay and poor working conditions.

So, what can we do as consumers to make sure our beloved smartphones do not have a negative impact?

1) Don’t upgrade your device unless you really have to. Even though it is tempting to replace your device as soon as the new version is released, it is best to use your old device until it really stops working.

2) Try to repair your device when it is broken. The two things that are most likely to break in your smartphone are the battery and the screen. Both can be replaced. Even though many current phone models cannot be taken apart and repaired easily, you can still try to repair the device yourself using YouTube tutorials. You can also send it to a shop for repair.

3) When you do have to part with your device, donate it to charity or sell it for example to a refurbishing shop. A lot of environmental problems are caused by mobile device disposal. Recycling is difficult because electronci devices contain so many different elements. Often they are sent to countries like Ghana, Nigeria or Vietnam for recycling. The easiest way to extract the valuable metals like copper, gold and aluminium is to take the devices apart and burn them. This process releases toxic chemicals into the air and the soil.

4) Consider buying a refurbished phone. From refurbishing companies you can get sturdy and cheap smart phones. None of the problems discussed above regarding mining and disposal are associated with them.

5) When buying a new device think carefully about what you want. Greenpeace’s ”Guide to Greener Electronics” is very useful if you want to buy a phone that has been produced sustainably. The guide rated the 17 world leading mobile device producers in the categories, Energy, Resource Consumption and Chemicals. The most sustainable device in their rating was the Fairphone made by a Dutch company with a grade B. It was followed by Apple in place two with a grade B-. A relatively young company producing more sustainable mobile devices is Shiftphone. This German start-up focusses on repairability and extending the lifespan os consumer electronics.

Match Boats

You will need

  • 1 Bowl
  • Washing-up liquid
  • 1 Match
  • Water
  • 1 Knife

What to do

  1. Fill the bowl with water.
  2. Split the match slightly at its lower end using the knife.
  3. Smear the split end with some washing-up liquid.
  4. Place the match in the water and watch what happens.
  5. The soap will dissolve slowly in the water which causes a backwards movement of the water molecules. This lets the boat move forward.
  6. If you want to repeat the experiment, change the water in the bowl and use a new match.

You can also watch this experiment here:

M&M Diffusion Experiment

Background

Diffusion is the movement of particles from a place of high concentration to a place of low concentration. We can also say that particles move from where there are lots of particles to where there are less particles.

In this experiment we are going to look at the diffusion of colour particles. You will observe the colour moving away from the sweets where lots of colour particles are found to places with less colour particles in the middle of the plate.

You will need

  • M&Ms or Smarties
  • Plate
  • Water

What to do

  1. Once you start this experiment, you cannot move it. So, make sure you choose a good spot to start.
  2. Pour the bag of M&Ms or Smarties onto your plate.
  3. Remove the sweets that landed in the middle of your plate.
  4. Place the remaining sweets in a circle around the outside of your plate.
  5. Remove any remaining M&Ms or Smarties that do not fit in the circle.
  6. Slowly add water to your plate. It needs to reach the M&Ms, but they should not float. From now on you cannot move the experiment.
  7. Observe what happens to the colour of the sweets.

You can also watch this experiment on YouTube:

Reading Exercise: Titration

Titration experiments can be used to produce pure salts by reacting acids and alkalis in a very controlled way. A neutralization reaction takes place where acid and alkali react to form the neutral products salt and water.

In a titration, the acid is added to a fixed volume of alkali, for example sodium hydroxide, in a conical flask. A burette is used to slowly drip the acid into the conical flask. The burette is a tall apparatus with a tap at the bottom that controls the flow of the acid (see image above).

A few drops of indicator are added to the alkali, so you can follow the reaction. The end-point is when the indicator changes colour. A single indicator like phenolphthalein is used because it shows only one very obvious colour change and gives you a sharp end-point. Phenolphthalein will change from pink to colorless at the end-point.

To obtain the pure salt, the water needs to be evaporated from the solution after the end of the titration by heating.

In industry, titration is used in many fields not only to produce pure salts, but also to test the amount of acids or alkalis in materials. For example, titration is very common to determine the amount of acids and alkalis in foods like chocolate. The method is also applied by construction companies to investigate the quality of building materials.

Questions

  1. What is produced by a titration experiment?
  2. Which reaction takes place generally during a titration experiment?
  3. Name the tall apparatus used to add the acid to the conical flask with the alkali.
  4. Which indicator can be used to identify the end-point of a titration experiment.
  5. Why is universal indicator not used to identify the end-point?
  6. What are the colours of phenolphthalein in an acid and in an alkali?
  7. What needs to be done after the titration to obtain the pure salt?
  8. Name two uses of titration experiments in industry.