4 What have I learned about acids and alkalis?

Summary: Tags: science oxford-science student-book-7 chemistry Created: 2026-05-19 Last Updated: 2026-05-19

In this chapter, you have:

• learned about Acids, Alkalis, and bases
• practised using indicators and the pH scale to find out how acidic or alkaline a solution is
• understood how to work safely with acidic and alkaline solutions
• explored Neutralization Reactions and how you can use these to make beautiful crystals
• learned about the important role of acid in the stomach, and how environmental scientists use bases to neutralize harmful acids in soils and lakes.

Journey through acids and alkalis What do I already know? - Chemical Formulae

• Elements and symbols This chapter - 4.1 Acids and alkalis
• 4.2 Indicators and pH
• 4.3 Neutralization
• 4.4 Making salts What comes next? - Chemical changes
• Useful Chemical Reactions

Table 2

1. Give the definitions of the key words. acid (1 mark)base (1 mark)alkali (1 mark)neutralization (1 mark)
2. A scientist measures the pH of samples of sweat, blood, and urine from one person. Copy Table 1. Decide if each sample is acidic, alkaline, or neutral. Table 1Name of mixture pH Acidic, alkaline, or neutral? sweat 5.3 blood 7.4 urine 6.8 (3 marks)
3. Joe wants to make a red-cabbage indicator. He has the equipment below. Full text alternative to the contentFull text alternative to the contentFull text alternative to the contentFull text alternative to the content First, Joe heats a mixture of chopped red cabbage and water. Write the letter of the best piece of equipment for this. (1 mark)Next, Joe filters the mixture. He keeps the solution. Write the letters of the best two pieces of equipment for this. (2 marks)Finally, Joe adds the red-cabbage solution to acidic and alkaline solutions. Write the letter of the best piece of equipment for this. (1 mark)
4. Figure 1 shows particles in two alkaline solutions. The dark blue circles represent alkali particles. The Light blue circles represent water particles. Figure 1 Full text alternative to the content Give the letter of the more concentrated alkaline solution. (1 mark)Explain your decision. (1 mark)
5. Table 2 gives the preferred soil pH of some fruit plants. Table 2Fruit plant Preferred soil pH blueberry 1.0–5.0 sweet cherry 6.0–7.5 cranberry 4.2–5.0 pineapple 5.0–6.0 strawberry 5.0–6.5 Name the plant that can grow well in alkaline soil. (1 mark)Name the plant that can grow in the most acidic soil. (1 mark)The soil pH in Andy’s garden is 6.0. Name three fruit plants that might grow well in this soil. (3 marks)The soil pH in Clare’s garden is 8.0. She wants to grow strawberry plants. State the type of substance she should add to the soil so that the pH is suitable. Explain your answer. (2 marks)
6. Describe and explain the stages in making magnesium chloride crystals from an acid and a metal. Include the names of the acid and the metal. (6 marks)