Kategori: Chemistry Education

Solubility Experiment

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Background

The general ruls of solubility is that ”like dissolves like”. This means that polar solvents like water will dissolve more polar compounds such as ionic compounds like salts (e.g. sodium chloride). Less polar solvents such as organic solvents (e.g. propanone) will dissolve non-polar compounds such as plastics.

Nail polish contains non-polar compounds. Nail polish remover is made from propanone, a non-polar solvent which will dissolve nail polish, but not the polar ionic compound sodium chloride.

Method

1. Collect two watch glasses.
2. Brush some nail polish into the middle of the two watch glasses and let it dry.
3. Collect one beaker with water and fill a second beaker with propanone or nail polish remover.
4. Drop ¼ spatula of salt into the beaker containing water and stir. Observe what happens.
5. Drop ¼ spatula of salt into the beaker containing propanone and stir. Observe what happens.
6. Drop water onto one watch glass with nail polish and watch what happens.
7. Then drop some propanone or nail polish remover onto the 2nd watch glass with nail polish and watch what happens.

Results Table

Create your own results table.

Analysis

1. Explain your results.
2. What are weaknesses of the experiment?
3. How could you improve the experiment?

Make Your Own Ice Cream

Publicerat i Chemistry Education, Chemistry in the Home, Experiments at HomeLämna en kommentar

You will need:

  • Drinking chocolate powder
  • Salt
  • Cream
  • Ice cubes
  • Tea towel
  • Table spoon
  • Glass
  • Bowl
  • Milk

What to do:

  1. Mix one table spoon of drinking chocolate powder, two table spoons of milk and one table spoon of cream in the glass.
  2. Stir vigorously to dissolve the chocolate powder.
  3. Put some ice cubes in the bowl and sprinkle a lot of salt over them.
  4. Place the glass of ice cream mixture in the large bowl, on top of the salted ice cubes.
  5. Build up more layers of ice cubes and salt around the glass.
  6. Place the tea towel over the bowl for insulation. Leave the ice cream mixture to set for an hour.
  7. Take the glass out of the bowl and taste your homemade chocolate ice cream.

Background

Adding salt to ice will lower the temperature of the ice even more. This is a good way to freeze things without the freezer.

You can watch a video of this experiment here:

Chromatography at Home

Publicerat i Chemistry, Chemistry Education, Chemistry in the Home, Experiments at Home, Experiments/practicals for science lessonsLämna en kommentar

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:

Test the Flow of Liquids

Publicerat i Chemistry Education, Chemistry in the Home, Experiments at Home, Experiments/practicals for science lessonsLämna en kommentar

You will need

  • 3 Glass jars (empty and cleaned)
  • 3 Marbles (cleaned and dried)
  • If you don’t have marbles, use small rocks instead.
  • Water
  • Vegetable oil, for example olive oil or sunflower oil
  • Syrup or honey
  • Cooking oil and syrup or honey can still be used or eaten after this experiment.

What to do

  1. Fill each glass jar with a different liquid at least half full. Make sure that the liquids have the same height in each jar.
  2. Drop a marble into each one and observe how fast the marble falls through the liquid inside.
  3. The slower the marble falls, the higher is the viscosity of the liquid. Which liquid in this experiment has the highest and which the lowest viscosity?

Background

It takes much longer to pour syrup into a glass than to pour water. This is because syrup has a high “viscosity”. This means that it does not flow easily. The higher the viscosity of a liquid, the slower it will flow.

You can test the viscosity of a liquid by dropping a marble into it. The slower the marble falls, the higher is the viscosity of the liquid.

You can watch this experiment as a video here:

Red Cabbage Indicator

Publicerat i Chemistry, Chemistry Education, Chemistry in the Home, Experiments at Home, Experiments/practicals for science lessonsLämna en kommentar

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

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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

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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

Publicerat i Chemistry, Chemistry Education, Chemistry in the Home, Experiments at Home, Experiments/practicals for science lessons1 kommentar

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:

Home Experiment: Halloween Slime

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You will need

  • Bowl
  • Measuring cup
  • Spoon
  • 1 cup of cornflour
  • ½ cup of water
  • Food colouring (you can choose which colour)
  • Plastic container with lid for storage

What to do

  1. Measure out 1 cup of cornflour and place it in a bowl.
  2. Measure out ½ cup of water.
  3. Slowly add some of the water to the cornflour and mix with your hands.
  4. Then add some more water and keep mixing with your hands.
  5. Continue adding water and mixing until your slime has the right consistency.
  6. If gets is too runny you can add some more cornflour.
  7. Add about 10 drops of food colouring until your slime and mix it.
  8. You can store your slime in a plastic container with a lid. Your slime might still dry out a bit over time. If this happens you can just add some more water.

Background

Mixing cornflour and water gives you a slime that behaves very peculiar. If you touch it very lightly it feels liquid like water. If you hit it very hard and fast it feels solid like a rubber ball. The slime reacts differently depending on the force that acts on it. The bigger the force, the harder the slime. The smaller the force, the more liquid the slime behaves. These kind of liquids are called “non-Newtonian”.

You can watch the experiment as a video here:

Air Pressure Experiments

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You will need:

1st experiment:

  • Glass bottle
  • Balloon

2nd experiment:

  • One piece of card board
  • Glass
  • Water

What to do:

1st experiment:

  1. Stretch the opening of the balloon over the rim of the bottle’s mouth. Make sure that the body of the balloon is inside the bottle.
  2. Try to blow up the balloon.
  3. The air in the bottle has nowhere to go and pushes on the balloon. This increases the pressure in the bottle when you try to blow up the balloon and you will not be able to blow it up.

2nd experiment:

  1. Pour water into the glass until it reaches the rim of the glass.
  2. Place the piece of card board on the glass. Hold it down so the card board covers the rim all the way around.
  3. Still holding the card board, move above a sink.
  4. Turn the glass upside down while still holding the card board. Then let go of the card board.
  5. Air pressure forces the card upwards, against the glass. The pressure is strong enough to stop the weight of the water pushing the card away.

You can watch a video for this experiment here: