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pupils writing their own definitions of the terms matter , compress , volume and property ( slide 35 ). You could add other words of your own to this list if there are terms children muddled during the lesson. Assessment Can you draw a model for the particles in a solid, liquid and gas? WEEKS 3-6 Learning objective l Why do materials change state? Lesson three, or rather three lessons. This sequence is a set of five different investigations that explore how materials can change state. The running order below is one example, but the investigations are not sequential, so can be swapped about as staffing and time allow. There are a few introductory slides on the PowerPoint you may wish to share with your class before starting the series ( slides 36-43 ). Investigation 1 – Melting chocolate Time needed: 20 mins for the investigation and 40mins for de-rigging and writing. How better to get children excited and engaged than by putting chocolate in front of them? Read through slide 45 , introducing how the process of melting and tempering works, then start the investigation ( slides 46-50 ). First, get pupils to observe a square of chocolate floating in a bowl of water (make sure each group has water at a different temperature, so results can be compared). As you will be using boiled water, you may want a second adult for safety. I also recommend buying some small foil pie or cake cases for this (or you can fold your own from tin foil). You may want to try this out at home first, especially if using cheap chocolate; some budget own-brand chocolates are surprisingly difficult to melt. Given that each group only needs one square, you could stretch the budget for a better-quality chocolate. For the investigation, set your little chocolate-filled boat on the water. Record the starting temperature of the water, then ask children to observe the chocolate every two mins, making note of what happens to it using terms such as unchanged , changed shape , making a puddle and completely melted . It is important that all children use the same terms and quantify what these mean before and during the investigation. Allow time at the end for collating data on the class board for each group and get the children to copy it down (or provide a printout – see I1 in the downloadable resources for a table). Children can then write a few summary sentences. Investigation 2 –How do different materials melt? Time needed: 35mins for observing and 25mins for writing and setup. This activity is akin to watching paint dry for adults, yet somehow children love it. Over 35 minutes, watch how ice cubes made from squash, vinegar, cooking oil and milk melt, and make notes ( slides 51-55 ). I recommend putting food colouring or glitter in the water so you can tell it apart from the vinegar. There is a recording sheet, with suggested descriptive terms, in the download ( I2 ). Note: you will need to prepare the ice cubes in school. Vinegar melts rapidly and oil needs a very low temperature to freeze. The first time I did this, I made the ice cubes at home and assumed they would stay frozen in a cool bag during my 15min drive to work. I was wrong and it took ages to get the smell of vinegar out of my car! For watching the ice cubes melt, I recommend using a paint pallet, so the melting liquids don’t mix and cause other ice cubes to melt more quickly. Give the children stopwatches or put one up on your board. Children can observe every five mins using the given descriptive language. They could also try measuring the ice cubes in millimetres to give quantified measurements. After completing the investigation, children should summarise their observations. See slide 55 for prompts. Assessment Can you see any patterns in your collected data? Investigation 3 - How do we freeze ice cream? Time needed: Less than one hour. May need more depending on age of children or adult support available. Yes, we are making ice cream in the classroom – and it won’t be chaos! This is an experiment you may have already tried at home. All you need is: milk and sugar; two zip lock bags (one bigger than the other); ice and salt; and gloves. Put the sugar and milk in the smaller bag and ice in the larger. Then, put the smaller bag in the bigger one and cover the ice with salt. Gently shake the bags so that the salt (and then salty water) covers the ice, causing the ice to rapidly melt. Explain that the rapidly melting ice takes energy from its surroundings to change state, and that it is not the ice making the milk cold and creating ice cream, but rather the melting ice taking F EATURE S S C I ENC E www.teachwire.net | 23