Food Can Science
How children can work together and improve the environment.

Teacher Briefing

This unit links with QCA Science Curriculum concerned with the Characteristics of materials (Unit 3C).

It can also be used in conjunction with the unit Recycling Steel Cans also on this website to fulfil most of the objectives of that unit.

In addition this unit promotes Education for Sustainable Development. It introduces children, in simple terms, to the idea that some materials we use are finite and will eventually be used up, while others are renewable and can be replaced. Though aimed at younger Key Stage 2 children the worksheets in this unit could be used and extended with older pupils.

Teaching about materials and their properties by using food containers

Looking at food containers is a useful method of helping primary aged children identify different materials and understand some of their properties.

Materials such as paper, glass, metal, cardboard, plastic, wood and fabric are all used to package food products. However, whichever material is chosen to package the food there is a key concept that young children need to learn in order to understand the purpose of the packaging. i.e. Unprotected food is spoiled and contaminated by organisms that share our environment.

Although some of these contaminating organisms are clearly visible (flies, cockroaches etc.) many, such as fungi and bacteria, are microscopic.

Humanity learned to destroy contaminating micro-organisms by cooking food and to inhibit their growth by pickling, salting, sun drying etc.. However, as urban populations expanded and people travelled to parts of the planet remote from fresh food production, new methods of food preservation were needed.

At the turn of the 19th century it was discovered that fresh food sealed in containers and then cooked could be stored and used many months later.

The original preserving containers were made of glass but the weight and fragility of this material was an obvious problem. Iron and subsequently steel containers were stronger.

However in the presence of both moisture and oxygen these ferrous materials would both rust. This problem was solved by an electrolytic bonding of a thin layer of tin to the inside surface of the container and the "tin can" was born.

This product revolutionised the preservation and distribution of fresh food. The nutrients were sealed in the can and the product could be consumed many months later in an uncontaminated state. Subsequently other methods of packaging and preservation using different materials have developed.

Other packaging materials

Aluminium cans are used for some products such as carbonated drinks. These are made from a single metal and share many of the properties of steel cans. i.e. They are light, strong and durable. However much more energy is used in the construction of aluminium cans than their steel counterparts.

Plastic packaging has enabled many products to be temporarily protected from contamination during distribution. However it is difficult to heat food and destroy micro-organisms in plastic containers because the later would melt! Similar problems would affect paper and card packaging.

Other food preservation methods

Refrigeration is now widely used to keep food fresh. When fresh food is frozen micro-organisms become inactive. Often the food is heated before freezing to destroy these organisms but the food will only be preserved while the freezing process is active.

Finite and Renewable materials

Many of the materials we currently use are finite and will be effectively exhausted at some unknown date in the future. It makes sense for children, in a simple way, to know the origins of the materials they use and then to sort out those that are finite from those that are renewable.

The finite raw materials are minerals from out of the ground. i.e. metals, most plastics, bricks, stone and cement and importantly fossil fuels (coal, crude oil, natural gas).

Renewable raw materials are those that are grown and derived from animals and plants. They include paper, wood, a few plastics and fabrics such as cotton, wool and hemp.

Of course at a more sophisticated level most of the products made from renewable materials have finite materials embodied in their manufacture. For example it is quite likely that a great deal of fossil fuel is used converting wood into paper. Then, if waste paper is recycled more finite fossil fuel is consumed in that process too.