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Grade 9

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Dear students,

Your midterm exam is coming very soon. With this, please answer the following questions as part of our revision and submit/upload your answer under classwork - TASK 5: Science Revision - Chemical Reaction, Changes and Equations.

Task 5: Science Revision

Directions: answer the following questions listed below and upload your work under the classwork section of the google classroom and be ready to discuss your examples in the online class.

1. Every chemical change alters the identifying properties of the original substance. Other signs are the following listed below. Explain and give examples of each of the evidence of chemical change. (10 points)

1.1 Evolution of heat and light -

1.2 Evolution of gas -

1.3 Formation of a precipitate -

1.4 Production of mechanical energy -

1.5 Production of electrical energy -

2. Look around your house, like in the kitchen and in the garden. Observe and list at least 5 changes and point out evidence which prove that a chemical reaction has taken place. (5 points)

3. PHASE CHANGES IN PRESENT-DAY TECHNOLOGY (School Theme: World of Technology)

For example: water, when heated to its boiling point, changes to vapor or steam. The steam can be used to run machines like the steam engine in boats or trains. On large-scale technology, water from the ground changes to geothermal steam and is used to power turbine generators producing electricity.

3.1 Give one specific example of PHASE CHANGE in present-day technology. Indicate the project or the technology applied. (2 points)

3.2 Briefly explain the processes and functions. (5 points)

3.3 State the importance of the technology in everyday living. (5 points)


Most industries make use of chemical reactions that change raw materials into more useful products. To mention just a few, these are the industries which produce soap, paper, glass, rubber, plastics, cement and textile.

4.1 Identify one specific example of any manufacturing industry using chemical changes. (5 points)

For example: Manufacturing of "CEMENT" - cement, as you are very well aware of, is one of the materials used in making concrete. In common usage, cement refers to 'portland cement'.

'Portland cement' is a closely controlled chemical combination of limestone (calcium carbonate) and clay (silica and alumina) with iron oxide and small amounts of other ingredients. Gypsum is added to this mixture in the final grinding process in order to regulate the setting time of the cement when mixed with water.

There are three stages in the commercial manufacture of cement, namely: (1) preparation of the natural materials; (2) heat treatment; and (3) clinker cooling and grinding.

Transformation of cement into concrete is done by mixing it with sand, gravel and water. The addition of water triggers a series of chemical changes that bind the materials together. The result is concrete, a product of such hardness and resistance to compression and tension that it has become one of the most useful structural materials of this industrial age. Home made concrete materials have improved our quality of life. Compared to one made of wood which is not environmentally friendly, concrete takes even a lifetime before a concrete house to deteriorate. Concrete houses or buildings can also withstand harsh elements of weather.

5. Explain the "Law of Mass Conservation" Give one example of chemical reactions indicating the reactants and the product(s). (5 points)

All the best.

See you in our synchronous learning.

Mr. Elmar Rubio

Secondary Science Teacher

Thanyaboon Boonkoed

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