Acids and Bases Science 9 PDF

Acids and Bases Science 9 After this lesson I will be able to… - Compare acids and bases - Identify acids and bases based on pH - List pH indicators and describe ways to use them - Discuss the effects of acid rain and ways to neutralize acids  What are acids and bases? Acids:...

Acids and Bases Science 9 After this lesson I will be able to… - Compare acids and bases - Identify acids and bases based on pH - List pH indicators and describe ways to use them - Discuss the effects of acid rain and ways to neutralize acids  What are acids and bases? Acids: Bases: ◻ Chemicals that produce ◻ Chemical s that produce acidic substances -pH less basic substances- pH more than 7 than 7 What are the properties of acids and bases? Acids Bases ◻Taste: Sour ◻ Taste: Bitter ◻Feels: Stings ◻ Feels: Slippery ◻Acidic: adjective ◻ Basic: adjective used to describe acids used to describe bases Tasting and feeling unknown chemical are UNACCEPTABLE methods of identification. Indicators ◻ Are substances that have a colour change when they react with acids and bases ◻ What is an example will we seen this year? ⬜ Bromothymol Blue ⬜ Universal Indicator (has a range of colours based on pH) Litmus- A chemical indicator ◻ Mixture of plant compounds ◻ extracted from certain lichens ◻ Looks light pink before reactions ◻ In the presence of acid it turns red. ◻ In the presence of base it turns blue ◻ This is not an exact value… it just give an approximation of how acidic or basic a substance is Neutralization Acids and bases react together when they are mixed. This type of reaction is called Neutralization. Both the acid and the base are used up in this type of reaction. A salt and water are produced. pH Scale ◻ More specific way of comparing acids and basis ◻ Scale is from 0-14 ◻ pH: 7.0 is neutral ◻ Lower than 7 is acidic, higher than 7 is basic ◻ Each pH unit represents a 10 fold increase in acidity or alkalinity pH Scale Universal indicator or pH paper will change a colour characteristic of a certain pH ⬜ Colours are matched against a chart that shows the range of colours for known pH values. Rainwater is naturally slightly acidic. When this water combines with chemicals in the atmosphere such as sulfur dioxide or nitrogen dioxide, the effect results in Acid Rain(with a pH as low as 3 ­in some parts of Canada) This can have devastating effects on living organisms. Normal Rain/Snow = pH of 5.6 Anything lower than the normal is to be considered ACID RAIN/SNOW ∙ When acid rain/snow enters the water system it affects the acidity of the water, resulting in a decrease of diversity among surrounding plants and animals ** When acidic deposits build up over the winter and melt in the spring this can dramatically lower the pH of the water 12 ** Process is referred to as SPRING ACID SHOCK What is Acid Rain? ◻ Rain and Snow containing acidic compounds ⬜ H2SO3(aq) Sulfurous Acid ⬜ H2SO4(aq) Sulfuric Acid ⬜ HNO2(aq) + HNO3(aq) Nitrous and Nitric Acid ⬜ H2CO3(aq) Carbonic acid Neutralizing Acid Using Chemistry to Control Acid Effects ◻ Scrubbers ⬜ Use limestone mixed with water. ⬜ Toxic gases are passed through this mixture that absorbs sulfur particles, preventing them from entering the atmosphere.  Using Chemistry to Control Acid Effects Catalytic converters ⬜ They contain a ceramic or wire honeycomb coated in a metal such as platinum that act as a catalyst for complete combustion ⬜ The converter aids in the formation of carbon dioxide and water so that less carbon monoxide and nitrogen oxides are produced 20 Check and Reflect (pg.195, see next slide) Questions: 1-5 19