CHAPTER 17 – COMPOUNDS, MIXTURES AND SEPARATION OF MIXTURES Molecules
When atoms are chemically joined together by bonds, they sometimes form molecules. A molecule is a group of two or more atoms bonded together. A molecule is the smallest part of an element or compound that has the chemical properties of that element or compound.
Oxygen molecule
Water molecule :Fig. 17.2 Molecules
• Oxygen is an example of an element made up of molecules. It is made up of two oxygen atoms bonded together.
• Water (two atoms of hydrogen bonded to one atom of oxygen) and carbon dioxide (one carbon atom bonded to two oxygen atoms) are examples of compounds made up of molecules, as they contain two different types of atoms.
Mixtures
A mixture is made up of two or more elements or compounds that are physically combined. For example, seawater is a mixture of water and salt. The substances in a mixture can be separated easily from each other without a chemical reaction taking place.
:Fig. 17.3 Model of a mixture
? TEST TUBE
3. Copy the following table and use your knowledge of elements, compounds and mixtures to classify the following substances into the categories in the table below: magnesium air
water hydrogen Element
saltwater iron oxide
Compound
chlorine sulfur
diet cola Mixture :Fig. 17.4 Seawater is a mixture
Carbon dioxide molecule
4. Copy the following table and name the elements that make up the following compounds. Use the periodic table to help you with this activity.
Compound Water Carbon dioxide Sodium chloride (table salt)