Acids, Bases and Alkalis

Material Changes

Sec 1

​Learning Objectives

​1. Recognize the properties of acids and alkalis.

​2. Use a pH scale

​3. Understand neutralization and some of its application

​4. Use indicators to distinguish acid and alkali solutions

What is acid?​

Can you give an example?​

​Acids are everywhere

Many things contain acid. Some foods also contain acid.

1. ​They have sour, sharp and tangy taste

2. ​Examples: Lemons and limes, because they contain citric acid (weak acid)

3. ​Common acid in the laboratory: hydrochloric acid, sulfuric acid and nitric acid

Open Ended

Name a food surround you that contains an acid. Describe the test of it.

​Some acids are dangerous

1. ​Strong and corrosive

2. If strong acid gets on your skin it will dissolve it. You will get a chemical burn.

3. ​Acids can be diluted with water, this makes them less dangerous, but they still irritant and harmful.

4. ​Thus, if you spill the acid, wash the area with lots of water.

5. ​Can you notice something on the figure?

​

Multiple Choice

Acid in our stomach?

• Hydrochloric acid

• Acetic acid

• Sulfuric acid

• Carbonic acid

Multiple Choice

Acid in soft drink?

• Hydrochloric acid

• Sulfuric acid

• Carbonic acid

• Acetic acid

What is alkalis?​

​Can you give an example?

​Alkalis are everywhere

​Many cleaning products contain

1. Taste (often) bitter and feel soapy or slippery

2. ​Examples: toothpaste and households cleaning products

3. ​Common alkalis found in the laboratory are sodium hydroxide, pottasium hydroxide and calcium hydroxide.

​​Some alkalis are dangerous

1. ​​Strong alkalis are corrosive

2. If strong alkalis gets on your skin it will dissolve it. You will get a chemical burn.

3. ​Alkalis can be diluted with water, this makes them less dangerous, but they still irritant and harmful.

4. ​Always wear eye protection when using alkalis.​

5. ​Can you notice something on the figure?

Acids and alkalis are chemical opposites.​

They can cancel each other out when they are mixed together.​

Multiple Choice

Which substance is alkali?

• Toothpaste

• Lemon juice

• vinegar

• soft drink

Open Ended

What does corrosive mean?

Working safely with acids and alkalis.

Can you tell what are the tips?​

​Working safely with acids and alkalis.

1. ​Stand up to work. why?

2. ​wear safety glasses. why?

3. ​take the top off the bottle and place it upside down. why?

4. ​replace the bottle top as soon as you finish using the bottle. why?

​Deciding acid or alkali substance

We can use:

1. Handmade indicator, and

2. Litmus​ paper

​Let's see your course book page 92.

​

​Indicators can be made from brightly colored berries, flowers and other parts of plants, ex: red cabbage, blackcurrant and beetroot

​Litmus is an indicator that turns red in acids, blue in alkalis and purple in neutral (pure water).

Multiple Choice

What is the solution tested by litmus paper?

• an acid

• a base

• A pH-neutral substance

• a buffer

​The pH scale

Litmus shows if a substance is an acid or an alkali, while

Universal indicator shows how acidic or alkaline a substance is. This indicator can change to many different color

The strength of acids and alkalis is measured on the pH scale.

​Universal indicator changes color and shows the pH of a substance

Multiple Choice

Apart from litmus paper, what other laboratory substance can you use to test if colourless substance is an acid or an alkali?

• Catalyst

• universal indicator

• salt

• water

Multiple Choice

What is the pH of distilled (pure) water?

• 12

• 3

• 7

• 8

Multiple Choice

Which pH level indicates a weak acid?

• 1-3

• 4-6

• 8-11

• 12-14

Multiple Choice

Which pH levels indicated a strong acid?

• 1-3

• 4-6

• 8-11

• 12-14

Multiple Choice

Which pH level indicates a weak alkali?

• 1-3

• 4-6

• 8-11

• 12-14

Multiple Choice

Which pH level indicates a strong alkali?

• 1-3

• 4-6

• 8-11

• 12-14

Multiple Choice

7 on the pH scale means that it is...

• acid

• base

• neutral

Multiple Choice

Soap is a weak base.  What is true about the taste of bases?

• they taste sour

• they taste bitter

• Incorrect

  they taste sweet

• Incorrect

  they taste salty

Multiple Choice

A common alkali used in the lab is

• hydrochloric acid

• hydrogen sulphate

• sodium chloride

• sodium hydroxide

What is ​neutralisation?

​

​Neutralisation in life

​1. Indigestion

​when stomach produces too much acid (hydrochloric acid) it can cause indigestion. To heal the pain we can use antacids which is an alkalis that can neutralize the excessive acid in stomach.

​​Neutralisation in life

​2. Toothpaste

​There are million bacteria in your mouth. This bacteria feed on the food pieces left on your teeth. The bacteria produce acid when they feed and cause them to decay. Toothpaste is alkali and help to neutralize the acid on your teeth.

​Investigating acid and alkali

​1. Asking questions

​

​2. Planning an investigation

​

​3. Result

​