User talk:KADARI

Chemistry (Elements, Compounds and Mixtures) 1. A compound forms when two or more elements combine. A chemical change takes place when elements combine to form a compound. In a chemical change, new substances with new properties are formed.

2. A physical change is a change in which the appearance of substance changes, but the properties stay the same.

3. Molecules of the same compound always contain the same elements. The atoms in the molecules of the same compound always combine in the same numbers.

4. An electron moves in a certain energy level around the nucleus of an atom. Each energy level can hold only a certain number of electrons. Electrons fill the energy levels in order.

5. Different elements have electrons in different numbers of levels. Atoms share, borrow, or lend electrons to other atoms in order to form compounds.

6. An atom that has a charge is called an ion. Ions with opposite charges attract each other.

7. A chemical formula is used to show many atoms of each kind are in a compound.

8. A radical is a group of elements that behaves as if it were one element.

9. In naming a compound, use the name of the first element and the name of the second element with the ending changed to –ide.

10. Acid are compounds that contain hydrogen, react with metals to form hydrogen, and have a sour taste.

11. Bases are slippery compounds that contain hydrogen, react with metals to form hydrogen, and have a sour taste.

12. Bases are slippery compounds that contain the hydroxyl radical, and have a bitter taste.

13. Indicators can be used to test for acids and bases.

Write the meaning of the following words as used in science.

1. Chemical change	2. Chemical formula

3. Indicator			4. pH	5. Radical

6. ion 		7. Physical change  8. Subscript

9. Base		10. Acid