Classifying Chemical Compounds What are the properties of Ionic compounds, molecular compounds, acids, bases and salts?

Ionic compounds are made up of ions Molecular compounds are made of molecules containing atoms that are covalently bonded. Ionic and molecular compounds have different properties Ionic compounds form hard crystals with high melting points and conduct electric current when dissolved in water or melted. Molecular compounds do not conduct electric current when melted or dissolved in water and have lower melting and boiling points

Ionic compounds form solids by building up repeating patterns of ions Ionic compounds form solids by building up repeating patterns of ions. They form a 3 dimensional arrangement called a crystal. Many crystals of ionic compounds are hard and brittle. Ions in an ionic compound must break apart for the compound to melt. It takes huge amount of thermal energy to separate the ions in a crystal. Compared to an ionic compound, a molecular compound needs less heat to separate the molecules because the forces holding them together are weaker. Molecular compounds have much lower melting and boiling points.

In essence: A typical ionic compound is a crystal, hard and brittle. Melting points of ionic compounds are high. They conduct electricity when they are dissolved in water or melted. Molecular compounds do not conduct electric currents and have lower melting points and boiling points

Electrical conductivity(property of ionic compounds): electric current is the flow of charged particles. Example: what happens to salt when it is dissolved in water? The ions of sodium and chlorine become far apart that their opposite charges don’t hold them in fixed position anymore. The ions can move carrying current. In general any food containing saltwater could be used to conduct electric current

Page 377 – apply it. Students working in groups answer questions 1,2,3

Acids are compounds with specific characteristic properties. An acid reacts with metals and carbonates, tastes sour and turns blue litmus paper red. A compound that changes color when it comes into contact with an acid is called an indicator. Many common items contain acids. Folic acid is in green vegetables. Hydrochloric acid is in your stomach helping with your digestion. Sulfuric acid is in batteries. Acids react with metals to produce hydrogen gas.(examples: iron, copper, zinc. Gold and platinum do not react).That is why acids are described as corrosive. Sour taste is a characteristic of acids( lemons, vinegar, grape juice, tomatoes)

Bases another group of compounds is the opposite of acids A base tastes bitter, feels slippery and turns red litmus paper blue. Common bases include ammonia found in household cleaners, and baking soda. Unlike acids, bases don’t react with metals or carbonates. Bitter taste: example tonic water. Slippery feel: soaps, shampoos, and detergents that contain bases. Indicators: bases turn red litmus paper blue. Main difference between acids and bases is that acids release hydrogen ions when dissolved whereas bases release hydroxide ions when dissolve. A common misconception is that only acids not bases can cause physical injury. Example a drain cleaner that contains a very strong base and that can injure the skin, eyes, nose mouth.

Neutralization is a reaction between an acid and a base Neutralization is a reaction between an acid and a base. It produces salt and water. It involves a positive ion of a base and a negative ion of an acid which cancel out or neutralize each other. Salts are made of ions and share the properties of ionic compounds, i.e. crystal shape, high melting and boiling points, and electric conductivity. Students work in groups on page 380 .Answer question about how can bonding determine the properties of a compound and water H2O.

Acids and bases can be measured using the pH scale. The pH scale ranges from 0 to 14. Most acidic substances are found at the low end of the scale while bases are found at the high end. You can find the pH of a substance using indicator paper, which changes color for each pH value. A pH lower than 7 is acidic. A pH higher than 7 is basic..If it is exactly 7 is neutral, neither acid nor base. Water and salts are neutral. Students work in groups on page381 to answer section “assess your understanding”.

Home learning: Create a poster that shows examples of common acids and bases. Create your own art. Review the properties of acids and bases so you can make appropriate selections. Use a cardboard or construction paper.