Some other substances find great difficulty to react with oxygen like silver, platinum and gold since they are not active; so these substances are used in making jewels. Also substances, like gold and silver, which are chemically poor active are used to cover other substances which rapidly gain rust, as iron to protect them from corrosion. Life Applications
1. Painting metallic bridges and the light posts in streets from time to time in order to protect them against rust. 2. Spare parts of cars are coated with grease to protect them getting rust. 3. Cooking aluminum pots are washed using a rough material to remove any layer formed on the pot surface.
Optional Activities: Choose one of the following activities, share a group of classmates to perform, then ask your teacher to evaluate and add it to your portfolio. 1. Write a list of some substances then compare their characteristics. 2. Write a report about life applications of some substances 3. Write a scientific essay about the negative impact of iron rust which causes economic loss and how to overcome.?
Summary • Density: mass of unit volume of a substance • Melting point: it is the temperature at which a substance changes from a solid state into a liquid one. • Boiling point: it is the temperature at which a substance changes from a liquid state into gaseous one. • Substances differ in their characteristics as: colour, taste, smell, density, melting and boiling points, hardness, thermal conduction, and electric conduction. • Substances have different chemical activities. First Term