SOLIDS

Let’s grow a solid

Supports National Curriculum, Key Stages 1 and 2, Units 4D, 5C and 5D

Suitable for years 4,5 and 6.

The time for the session is approximately 1 hour. The length of the session can be varied by modifying the PowerPoint presentation once downloaded.

Outline of content

  • Establish what the children already know, using a demonstration
  • Explain differences between solids and liquids
  • (Different materials change from liquid to solid at different temperatures)
  • Solids remember how they grew
  • There are two types of frozen water, formed in different ways: a) snow and b) ice
  • a) Formation of snowflakes using an on-line computer simulation
  • b) Formation of (close packed) crystalline solids using a game and bubble rafts
  • Bubbles are very different to either water or air because they are a sandwich
  • Special solids can be grown using MB(Molecular Beam Epitaxy) which are used in computer chips etc.

Points to note:

Please read the notes about risks and agree the assessment with the teacher before the session!

Cross References

  • The slides in the PowerPoint presentation are referenced in the plan.
  • As the presentation may be running throughout the session some simple slides provide a suitable background, alternatively switch to a black screen
  • Apparatus details are below the table and are linked to the relevant sections.
  • Risk assessments are below the table
  • Vocabulary: The presentation uses expressions included in the KS 1&2 strategies
  • (NB It also uses terms not introduced until KS 3.)

Misconceptions to be corrected

  • Crystal surfaces are not formed naturally
  • Ice, snow and water are different materials
  • Solids such as crystals cannot be melted
  • Freezing and melting are not reversible
  • Children often confuse melting and dissolving. This presentation explains melting.

Let’s Grow a Solid

The children can take advantage of a ‘live’ demonstration by asking lots of questions – please use the ‘discussion’ notes to encourage them to do this!

Activity / Discussion / Aims/Facts
Slide 1.Start by an activity to attract their attention.
Use a spray bottle to spray water onto a cloth that changes shade of colour when it is wet.
Then try to spray using the bottle containing the ice.
(apparatus list for activity 1.) / Ask them what changes they see. Encourage answers about liquids being able to change shape so is squeezed out of the spray.
Ask what is different. Encourage statements about solids not changing shape therefore it is not possible for the ice to be sprayed from the bottle. / Aim to find out what they know and to establish the difference between liquids and solids..
Use slide 2to reinforce that solids do not change shape when you move them.
The natural object is Stannage Edge in Derbyshire, a natural rock formation.
The crown links well with crystals shown later in the presentation. / There are numerous different sorts of solids.
(Be prepared for questions about paper or springs which are flexible and solid.
Solids can be forced to change shape.) / Solids have a fixed shape.
Show a melted candle or piece of chocolate.
(apparatus list for activity 3.)
Use slide 3to reinforce that liquids have no shape. The atoms in the liquid can move around freely.
Talk about atoms being very tiny particles. / Ask what happens when they keep chocolate in their pocket on a hot day. Use this to lead into a discussion about melting being the change from a solid to a liquid. (Different solids melt at different temperatures. Ice melts at 0oC, iron at 1535oC.) / Liquids take the shape of the container. A solid melts to form a liquid.
Tell that solids are amazing because they ‘remember’ how they grew.Slide 4
Eg as water freezes it can form 2 types of solid –snow/frost and ice / Ask them whether they have seen frost on car windscreens on frosty mornings and icicles etc
Use slides 5 and 6 to encourage the children to recount what they have seen and link the solids with water. / The same material can exist as both solid and liquid.
Show two glasses of water and explain that one is water from the tap and the other from melted ice. Ask whether they can tell the difference. Slide 7 / Discuss how the water in each is formed. The melted ice was solid before it melted. The water from the tap was rain so formed from condensed water vapour. / Liquids do not have a memory of how they are formed.
Explain that during the session they will learn about two ways solids grow.Slide 8 / This is useful because scientists can grow solids atom by atom in special ways to do special tasks.
Type 1 Slide 9Snow flakes
The atoms add on exactly where they hit.Slide 10 / Talk about the formation of clouds- that water vapour rises and forms clouds. When it is cold the water vapour freezes. Snowflakes grow as water molecules add onto others. / Liquids can be changed to a solid by cooling and this is freezing or solidifying.
Computer simulation
(slide, 11, 12 )
(Arrangein advance with the teacher that the site can be reached easily during the presentation the school may have to load java.) Show the molecules adding slowly at first so they see the molecules adding one by one. Then let them watch the fractal pattern building until there are about 100 molecules. Point out that it is not much like a snowflake. So add more. It begins to look like a flake when 10 000 molecules are in the flake.You can often minimise this program and then return to it at the end of the session to see how big it has grown. Note the easiest way to find the site is to put ‘DLA apricot’ into google –
Show slide 13 / Discuss the huge number of molecules in a flake. Thepattern produced on the site is a fractal.
Ask how they make snowballs. They will talk about squeezing the snow. Bring out that there are a lot of spaces in the snow. / Snowflakes are made of many thousands of ice molecules.
Solids formed in this way have spaces in them.
Type 2, ice
Slide 15
Emphasise that ice is hard. Slide 16 Explain that this is because of the way the ice was formed from water. / Ask whether they have ever jumped on a frozen puddle. Ask what the flakes of ice are like:hard, see-through, sharp edges, flat sides. Ask them if they have ever felt under the ice from a puddle and noticed how very smooth it is. Compare with the pictures of crystals. Slide 16 / Solids formed in this way have very smooth sides and are very hard.
Slide 17 Explain that the crystals have atoms in layers- that just as they have learned that atoms are very small- the layers are very thin. About 10,000 layers are needed to get the thickness of a piece of paper. / They are impressed by the large numbers. Explain that in the large piece of quartz crystal shown there will be 100 million layers! / The layers of atoms are very, very thin.
Slide18,19 Growing solids atom by atom artificially.
The temperature has to bejust correct to get the best structure. A beam of atoms is sprayed onto a surface and they move around to find the closest position / Discuss crystal growing kits (available from toy shops). Ask if they have ever grown crystals- they would have warmed the powder in the water and then leaved it to cool. Explain that just at the temperature where a liquid changes to a solid, the atoms can move around to find the best place so that they are all very close together. Show the BBC clip to show that some VERY big crystals can grow – if you leave them long enough! / Different solids melt at different temperatures.
On an Overhead projector, show discs being packed as close as possible together.
(apparatus list for activity 11)
Explain that when they are packed closely they form a solid – crystal. Slide 19 / When the discs all touch each near disc- there is only one possible pattern.
Class group activity.
(apparatus list for activity12)
Hand out about 12 discs per group. Ask them to place them together so that they are as close as possible. Do this on the OHP at the same time. Give them three narrow strips of paper and ask them to place them over the lines they can see. Use slides 21,22,23, 24to reinforce this. / They may suggest other structures but this is the closest packed and known as ‘close packed hexagonal’. Ask if they know the word hexagonal- some may link this with a hexagon. Talkabout the six sides and point out that each disc touches six others. / Atoms in a solid (crystal) are in a pattern which repeats many, many times.
Bubble rafts-slide 25
(apparatus list for activity 13)
Explain that we can find out more using bubbles. Go through the instructions with them using slide 26. Explain that they will need to be very sensible if this is to work because if they do not do it very carefully they will not get the effect. / The children will see that the pattern formed by the bubbles is similar to that formed in the previous exercise. They should slide the bubbles around carefully with their fingers to form a large raft.
Safety: If they ask can they do it at home, warn them to ask an adult to make the hole in the yogurt pot as it is difficult to push the pin through. / The atoms move so that they are packed closely in the pattern.
Such solids are hard.
Show slide27 and ask what they can see. Use slide 28to emphasise that the bubbles slide around to reach the best place. If a bubble bursts others will move so there is no gap.
Use slides 29 and 30 to show the rows clearly. / In the discussion compare with other natural structures. Ask where they have seen similar patterns and show the picture of the honeycomb- if available, take in a piece of honeycomb to show them.
Slide 30 / The close packed pattern formed by the atoms occurs many times in nature.
Discuss the bubbles. They are not like the soapy water, nor the air. The layers of bubbles could be built up to form a structure that is very different to either the water or theair. Show slide 32, then the picture of the foam dance. / They will mention bubble baths- task if they have been in a jacuzzi in the swimming baths- ask what would happen if bubble bath liquid were to be put into a jacuzzi. This emphasises that the structure of the water is different to that of air or water.
Slide 33Reinforce thatsoap films are very thin.
A thin film of water is very different from water in a bucket or glass.
We have a very thin sandwich
‘air- water –air’.
The bubbles behave like layers of atoms – which can build a crystal. / Talk about foam from soapy water. Bring out in the discussion that the bubbles will build something that cannot be made from just water or just air. / The bubbles behave like atoms building a solid.
Sandwich crystals can be made with the very special machine. Slide 35 These have different sorts of atoms in layers. These can do very special jobs.
Explain that computer ‘chips’ are made from these very special crystals.
‘Chips’ are used in lots of different items that they use. / Ask if they can spot some ofthem onslide 35?
iPods, games consoles, play stations, mobile phones etc all need these special crystals.
They make it possible for very complicated electrical circuits to be made that take up very little space. / Artificial crystals are used to make computer ‘chips’ which have numerous everyday uses.
Re-cap session / Slide 37 / Revise
Finish off saying scientists do amazing things.
Maybe leave them with some saturated salt solution and tell them that if the water evaporates very slowly they will get bigger crystals.
Slide 38 / Explain that early computers took up a large room which was filled with racks of equipment These computers could do about the same as a ‘calculator’.
Then asked whetheriPods made by the same technology be any use – as they would take up several rooms! / Scientists find out things and make new amazing things possible.
Explain that scientists find answers to questions.
They should keep asking questions.

IMPORTANT NOTES ABOUT HAZARDS AND RISKS

Water is used in the first demonstration because both the solid and liquid forms can be handled safely by the children. The original contents of the spray bottles are NOT suitable, so the bottles and spray heads must be washed thoroughly.

For the activity with counters or washers etc, the items used should not be so small that they might be swallowed. Washers are good because they have a hole in the centre which would allow air through if swallowed. Pennies are so familiar they unlikely to be tasted.

The bubble raft experiment uses washing up liquid which is safe for hands.

Care should be taken to ensure that the water is not spilled on the floor causing a child to slip.

If the children suggest that they would like to make bubble rafts in the bath, they should be warned that an adult should make the hole in the bottom of the yogurt pot.

APPARATUS

A data projector and white board/screen to show power point slides are required as well as an overhead projector. It is helpful if the overhead projector can be used at the same time as the power point slides.

Before the session connect to the website

ready for the computer simulation in activity 7. Arrange in advancethat the webpage can be downloaded and that the applet will run.If you use Goggle to search for ‘DLA apricot’ then the website comes up as nmber1.

The simulation shows fractals growing and has the options- Grow, Pause, Resume, Reset and Grow slowly. Practice before the session. It helps to start by showing the fractal growing slowly at first so the children see the particles adding slowly. Then explain that a snowflake has many, many more particles and show the quicker rate of growth. Stop it a few times to discuss whether there is sufficient detail for the structure to look like a snowflake.

Activity 1

  • 2 empty spray bottles of the sort for cleaning materials – well washed out.
  • Half fill with water
  • Bubble pack or other heat insulation material

Unscrew the top of one and squeeze some air out. Tighten the top and place the bottle in a freezer. Before the presentation, remove the bottle of ice from the freezer and insulate it with several layers of bubble pack or other good heat insulator to prevent the ice melting before the presentation.

Activity 3

Optional items to help to explain melting:

Melted candle,

soft chocolate

piece of pumice stone

Other items to help later explanations if available

  • crystals
  • honeycomb

Activity 5

Two transparent tumblers

  1. containing water which is melted ice and
  2. containing tap water.

Activities 12and 13

Demonstration

  • Overhead projector (OHP)
  • 3 narrow strips of paper (about 15 cm x 0.3 cm)
  • Discs to represent atoms
  • These could be washers about 1cm in diameter

or transparent discs, pennies, ‘tiddlywinks’, buttons etc

  • They must all be the same size.
  • Washers or transparent discs allow the strips of paper to be seen clearly during the demonstration on the OHP
  • Pennies are easily obtained for class use.

Linked class activity

  • small bags containing about 12 discs – one bag per group of children
  • 3 thin strips of paper or coloured plastic per group

Activity 14

Bubble rafts

  • washing up liquid
  • teaspoon
  • water
  • yogurt pots – 1 per group of children
  • large bowl – 1 per group of 3 or 4 children

[eg. washing up bowls, large ice-cream tubs (at least 3 litres), etc ]

  • Paper towels – for mopping up

Before arriving at the school make a small pin hole in the centre of the base of each yogurt pot. (Note: the hole should be made in advance because it is difficult to push the pin through. The hole should be as small as possible so that the bubbles are small. )

Before the session fill the bowls to a depth of about 8cm.

The detergent must be added very slowly to the water (NOT the water to the detergent) so no bubbles are formed. It is best to do this in advance and hand the bowls round at the appropriate time.

The water must be deep enough for the base of the up-turned yogurt pot to be below the surface of the water. If shallow containers are used then a small fromage-fraise pot is better.

Once the air trapped air has left the yogurt pot, a child can lift it carefully and put it back in the water to form more bubbles from the trapped air.

The children should guide the bubbles with their hands so they see them form a single layer and move to become close packed (anneal).