CHAPTER 2 ( SCIENCE ) : Elements, compounds and mixtures

Question 1

What is an element?

Answer 1

A substance that is made up of just one kind of atom

Question 2

What is a compound?

Answer 2

A pure substance made from more than one type of element that is chemically bonded together.

Question 3

What is a mixture?

Answer 3

A substance that is made of two or more different types of atoms that are not chemically bonded together

Question 4

Examples of elements :

Answer 4

Hydrogen, Carbon, Aluminium, Zinc, Magnesium

Question 5

Examples of compounds :

Answer 5

Water, carbon dioxide, sodium chloride, magnesium oxide

Question 6

Examples of mixtures :

Answer 6

Blood, soil, air, lemonade, alloys

Question 7

Each compound has a chemical name. The chemical name usually tells us the elements that the compound is made of.

Answer 7

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Question 8

• If the compound contains a metal, then the name of the metal comes first in the name of the compound.
• If the compound contains a non-metal, the non-metal name is usually changed. For example, the compound made from sodium and chlorine is not sodium chlorine, but sodium chloride.
• When two elements form a compound the name often ends with “ide”.

Answer 8

.

Question 9

Carbon dioxide -

Answer 9

CO2 - Carbon, Oxygen

Question 10

Magnesium oxide -

Answer 10

MgO - Magnesium, Oxygen

Question 11

Water -

Answer 11

H2O - Hydrogen, Oxygen

Question 12

Ammonia -

Answer 12

NH3 - Nitrogen, Hydrogen

Question 13

Sodium Chloride -

Answer 13

NaC1 - Sodium, Chlorine

Question 14

• Sometimes, compounds contain two different elements, plus a third element - oxygen. These compounds have names that end with “ate”.
• For example, a compound of calcium, carbon and oxygen is called calcium carbonate.

Answer 14

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Question 15

Which two elements are combined in hydrogen sulfide?

Answer 15

Hydrogen and Sulfur

Question 16

Which two elements are combined in magnesium oxide?

Answer 16

Magnesium and Oxygen

Question 17

A student wrote this name for a compound which was made of calcium and sulfur : sulfur calcium. What is wrong with this name? Write the correct name for the compound.

Answer 17

Calcium is a metal, therefore Calcium must come first. So, it is Calcium Sulfide.