Read the following descriptions and guess the name of the element

1. ___________ is an alkaline earth metal and one of the most abundant elements found in the Earth's crust in terms of mass. This soft gray element is rather hard, and it is important for life on earth. It is the main component in the mineralization of shells and bones, and the most abundant element of all by mass in many living organisms. The element is an important constituent of teeth, leaves, and bone.

2. ___________ is a chemical element and the most abundant and lightest element of all. It constitutes about 75 percent of the elemental mass in the universe. This element, found in plasma state, is the main element in the composition of stars in the main sequence. It is the main component of all organic matter and water.

3. _____is a solid metal that belongs to the group of the alkaline earth metals and has no stable isotopes. Naturally occurring element is found in animals, plants, water, soils, and rock. While the element is present in uranium ores, it is a scarce one. The element was discovered in 1898 by Marie and Pierre Curie.

4. ___________ is a member of the alkali group of metals. It is soft, silvery-white in color and the least dense and least heavy element of all the solid elements. It is highly flammable and reactive, which is why it is usually conserved in mineral oil. This element never occurs freely in nature, It is often obtained from clay.

5. ___________ is the only metal in a liquid state at standard conditions for pressure and temperature apart from bromine. This element is a fair conductor of electricity, but at the same time, it is a poor conductor of heat. The metal is used in scientific instruments, barometers, and thermometers.

6. ___________ is a chemical element, which is tetravalent and nonmetallic. It is among the few elements that have been known to people since antiquity. It has several allotropes. Depending on the allotropic form, its physical properties can vary widely. It is an element with key importance to all living systems and life, in its present form, would not exist without it.

7. ___________ occurs as a pure crystal as well as in many minerals. This element is a metalloid and is found in different allotropes. Metallic form is mainly used to strengthen alloys of lead (e.g. in automotive batteries) and copper. IT is also among the most commonly used semiconductors. Is compounds are employed in the production of insecticides, herbicides, and pesticides. It has a toxic effect on more complex life forms.

8. ___________is a chemical element and an inert noble gas, which gives a red-orange glow to advertising signs, low-voltage glow lamps, and high-voltage discharge tubes. This element is the 2nd lightest noble gas, with the narrowest liquid range of all elements.

9. ___________is a halogen element, poisonous greenish-yellow gas. Occurs widely in nature as a sodium compound in seawater. One of its compounds is widely known as everyday table salt. It ion itself is part of the salt in the earth and in the oceans. In fact, almost 2 percent of the seawater mass is made of its ions

 

Speaking: Work in pairs. Give similar descriptions of three chemical elements.

UNIT IV. MATTER.

1. Discuss the following questions:

1. What is matter?

2. What states of matter can you name?

 

Read Text A. What is the meaning of the expressions in bold?

Text A. States of matter.

There are four main states of matter: solids, liquids, gases and plasmas. Each of these states is also known as a phase. Elements and compounds can move from one phase to another phase when special physical forces are present. One example of those forces is temperature. The phase or state of matter can change when the temperature changes. Generally, as the temperature rises, matter moves to a more active state.

Phase describes a physical state of matter. The key word to notice is physical. Things only move from one phase to another by physical means. If energy is added (like increasing the temperature or increasing pressure) or if energy is taken away (like freezing something or decreasing pressure) you have created a physical change.

One compound or element can move from phase to phase, but still be the same substance. You can see water vapor over a boiling pot of water. That vapor (or gas) can condense and become a drop of water. If you put that drop in the freezer, it would become a solid. No matter what phase it was in, it was always water. It always had the same chemical properties. On the other hand, a chemical change would change the way the water acted, eventually making it not water, but something completely new.

 

3. What is a ‘phase transition’? Read Text B and fill in the gaps with the following terms:

a) ionization

b) sublimation

c) freezing

d) deionization

e) melting

f) vaporization

g) deposition

h) condensation