Gr7 Technology (2024)

Right now, you are sitting at a desk on a chair. Soon, you will write things in a book with a pen or a pencil. The book rests on your desk. All these objects are called structures. If you look around the classroom, you will see many other structures. For example, the classroom and the school buildings are structures.

In this chapter, you will learn about natural and man-made structures. You will also learn about shell structures, solid structures and frame structures.

Things called structures

Look around you in the classroom. Choose any object, for example a cupboard, a table, a chair, a basket, a bottle, a shoe, a pencil case or a brick. Then answer the following questions about this object.

1. What is this object called?

2. What is it used for?

3. Can it be used to keep certain things in one place, so that they do not lie around all over the classroom?

4. Can it be used to protect something, for example to protect it from sunlight or wind?

5. Is it used to support something?

   

   This man is sitting comfortably on the chair. You can say that the chair supports the man and keeps him from falling off.

6. Describe two other objects that are different from chairs, but are also used to support something or someone.

A bridge that crosses a stream or a river from one end to the other helps people to cross it without getting wet. You can say that the bridge spans the stream.

A small business situation

Suppose you want to set up a stall at a market to sell food such as sugar, flour, maize, rice, eggs, beans and cooking oil. So you buy one large bag each of sugar, flour, maize and rice, and a 20-litre drum of cooking oil.

1. Make a list of the things you can see in this picture.

2. What else do you need to set up your stall before you can sell the goods?

   See Also

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3. What type of container will the eggs you sell come in?

   

4. Why are eggs packed in special containers such as the one you see in this picture?

5. If you wanted to make a table from the two empty crates, what else would you need?

6. Suppose a woman wants to buy 2 kg of flour from you. Will you ask her to hold out her hands so that you can put the flour in her hands, or will you make another plan?

7. What will you use as containers when you sell maize, rice, sugar and flour to people?

   A container is something that you use to keep things together in one place, like a paper bag for rice.

8. What will you use as a container to sell oil?

9. What did you decide to use to span the two crates to form a table, when you answered question 5 above?

   The table you will make, the crates that you use to make the table, the containers in which you get the eggs and the plastic bottles in which you sell the oil are all called structures.

   There are many other things that are also called structures.

10. How will you protect yourself and the goods you sell when it rains? Draw the structure that you will use for protection.

    

    People design and make structures for different reasons. Many structures can help you to do one or more of the things below.

    To contain or hold something, so that it is not all over the place, and to keep it apart from other things.
    To protect something, so that it is not damaged.
    To support something and hold it up.
    To span the space between two objects so that they are connected.

11. Can you think of a structure that can do more than one of these things?

Man-made and natural structures

Have you ever looked closely at a termite mound? It really is wonderful how it contains and protects termites and their food against the weather and against their enemies. There is a whole city in there!

The material (soil) is reworked by them to make it harder so that it can withstand shocks, while its shape allows rain to flow off it easily. It is an example of a natural structure and it is not man-made.

Man-made shelters have the same functions - to protect people and their belongings. Before man-made shelters such as houses and tents existed, people used caves or trees for protection.

There are lots of different structures around us. Some are built by us and some are already there in nature. The termite mound is a structure, but it is not built by people. We call structures like that natural structures.

A cup that you use to drink tea or coffee is also a structure. It is a man-made structure because it was made by people.

Look at the structures on the next two pages, then classify them as man-made structures or natural structures.

Classify structures

1. Classify the 12 structures on the previous two pages as man-made or as natural structures.

   Man-made structures	Natural structures

2. What other natural structures can you think of?

3. Name any three man-made structures that provide protection.

4. Name any three man-made structures that provide support.

5. Name any three man-made structures that contain things.

Types of structures

There are three basic types of structures: shell structures, frame structures and solid structures. But some structures are a combination.

Shell structures

Most containers used to hold liquids or small solids are shell structures. Examples are coffee mugs, bowls for peanuts and bags for rice or sugar.

The strength of a shell structure is on its outside - in the shell.

Chicken eggs and empty ostrich eggs are examples of natural shell structures. Soccer balls or balloons are man-made shell structures.

Frame structures

A frame structure consists of different parts. These parts are combined in such a way to make the structure strong. A ladder and a bicycle are good examples of man-made frame structures. Spiderwebs are natural frame structures.

Solid structures

Structures like rocks, bricks and cement poles are solid. They do not consist of different parts with open spaces between them. A stone is a natural solid structure and is one piece of material. A brick is a man-made solid structure.

Combined structures