Protecting Polymers

Protecting Polymers Organiser’s Card About the activity This activity is designed to get children thinking about polymers and their different properties. Dr Polly Murs has asked for help to decide which cling film is best to cover her lunch. The foil she has been using keeps spilling her food! Can the children help by seeing which cling film is best? Through this activity you will support your group to: • Learn about polymers • Test the strength and durability of different kinds of cling film • Record and present their findings to the rest of the group Kit list • A selection of cling films (including PVC free cling film) • Aluminium foil • Lunch boxes or other containers • 50 gram masses to act as ‘weights’ • Rulers • Video camera or other equipment (e.g. mobile phone) to video the investigation • Freezer • Microwave What to do 1. Introduce the activity using the story. 2. Give out activity cards and equipment to the children. 3. Set the scene by discussing the email from Polly. Encourage the children to talk about cling film and foil. Do they use either at home? How do they bring packed lunches to school? 4. Give out samples of cling film and foil for the children to investigate. What similarities or differences can they notice? Encourage the children to make predictions. Do they think cling film will help solve Polly’s lunchtime problem? 5. Support children to conduct their investigation and make their own records of their results. Give each group a selection of weights, a container to stretch the materials over and a ruler. If possible allow each group to put a sample of their best material into a freezer to see what happens. They could microwave the cling film too. It is not safe to put foil in the microwave. Make sure children wrap each material being tested around the whole container. 6. Ask the children to present their findings to the rest of the group, they can be as creative in their presentation as they want.

Things to think about Testing foil and cling film against paper will help children understand the useful properties of polymers. For example water resistant, light weight and mouldable. Aluminium foil is more practical than cling film for protecting food in the freezer. It will hold its seal and is more likely to prevent freezer burn. The static electricity that helps cling film to stick can be demonstrated by hanging a piece of cling film off the edge of a table. Rub a plastic pen with fabric, then hold it close to the sheet of cling film. Can the children see the cling film move towards the pen? Keywords • Static • Durability • Polymers • Weights • Measures • Strength Watch out! Very important: do not put foil in the microwave. Find out more Cling film first entered the domestic market in the 1950’s. Cling film is made from thin plastic, so it is a good insulator. When you pull cling film off the roll, some of the electrons from one layer are pulled onto another layer, creating areas of positive and negative charge. The cling film holds this charge, causing it to be attracted to areas of opposite charge on other non-conductive materials such as ceramic plates. Aluminium foil has been used as a food covering since the 1930’s. Foil does not stick to other materials but can hold its shape when wrapped around food or other substances. Foil acts as a very good barrier to bacteria and odour. Cling film and foil are both used for many things other than food protection. Cling film is especially useful in medical settings. Often cling film is used to help treat burns, but it has many other uses. British Science Association Registered Charity No. 212479 and SC039236