Which of the following statements about acids is incorrect?

When litmus solution is exposed to an acidic pH, it turns red; when it is exposed to a basic pH, it turns blue. 

Properties of acids are

• Acids are sour to taste. 
• A litmus test is used to confirm the presence of an acid. 
• They are able to change the colour of litmus. 
• Acids are able to change the colour of the litmus paper from blue litmus to red when they are in contact with it.