Explanations

Using passive voice to organise information

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The use of passive voice in Cement

The following text from a science textbook tells how cement is made. The words in bold are verbs in passive voice .

Cement

Cement is made by mixing together three parts of broken up limestone and one part of clay with water.

The mixture passes into a long revolving kiln which slopes downwards. The mixture is heated and the water evaporates at 100^oC.

Further down the kiln, powdered coal or fly ash waste from electric power stations is added and the temperature is raised to 900^oC. Carbon dioxide is given off.

At the bottom of the kiln, the temperature is about 1500^oC, and a chemical reaction takes place between the limestone and clay which forms cement.

The cement is cooled and ground to a fine powder. A small amount (1-3%) of gypsum (calcium sulphate) is added. The cement powder is packed into bags and sealed.

(Adapted from Cheng, W.L. and Yeung, M.S. (1991) Modern Integrated Science 3. Oxford University Press, p 97.)

	Introduction
	The use of passive voice in Cement
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