Acids and Bases - Free Printable

Let’s go step by step to solve this worksheet.

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Part 1: Match the information with the correct term.

We’ll read each clue and match it to the best letter from A–O.

1. Color litmus paper changes to when dipped in an acid
→ Litmus turns RED in acid → M red

2. The type of ions released in a base
→ Bases release hydroxide ions (OH⁻) → H hydroxide

3. Color litmus paper changes to when dipped in a base
→ Litmus turns BLUE in base → D blue

4. Different substances used to determine a base or an acid
→ These are called indicators → I indicators

5. Naturally occurring plant used as an indicator
→ Turmeric is a common natural indicator → O turmeric

6. Naturally occurring indicator orange in color
→ China rose gives pink/orange colors → E China rose

7. Type of liquid that releases hydrogen ions
→ Acids release H⁺ ions → B acid

8. Hydrogen and hydroxide ions are equal in this type of liquid
→ That’s neutral water → L neutral

9. Litmus is made from organisms that come from alga and fungus
→ Those are lichens → J lichens

10. Type of liquid that releases hydroxide ions
→ Bases do this → C base

11. The type of ions released in an acid
→ Hydrogen ions → G hydrogen

12. A scale used to determine the level of acidity or base
→ pH scale → N pH

13. Found in the stomach of a person used for digestion
→ Stomach has hydrochloric acid → F hydrochloric acid

14. A Latin word that is translated to acid
→ “Acere” means sour/acid in Latin → A acere

15. Type of paper used for measuring the acidity or base of a liquid
→ Litmus paper → K litmus

✔ So matching answers:

1 – M
2 – H
3 – D
4 – I
5 – O
6 – E
7 – B
8 – L
9 – J
10 – C
11 – G
12 – N
13 – F
14 – A
15 – K

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Part 2: Compare liquids — circle whether more or less acidic/basic

We need to know relative strengths:

- Gastric acid = very strong acid (pH ~1.5)
- Urine = slightly acidic (pH ~6)
→ So gastric acid is more acidic than urine → more

- Milk of Magnesia = weak base (antacid, pH ~10.5)
- Bleach = strong base (pH ~12–13)
→ Milk of Magnesia is less basic than bleach → less

- Soapy water = mild base (pH ~9–10)
- Ammonia = stronger base (pH ~11–12)
→ Soapy water is less basic than ammonia → less

- Black coffee = acidic (pH ~5)
- Orange juice = more acidic (pH ~3.5)
→ Coffee is less acidic than orange juice → less

Wait — question says: “Black coffee is (more or less) acidic than orange juice.”
Orange juice is MORE acidic → so coffee is LESS acidic → less

But let’s double-check: lower pH = more acidic.
Orange juice pH ≈ 3.5, Coffee ≈ 5 → yes, coffee is less acidic → less

- Lemon juice = very acidic (pH ~2)
- Orange juice = also acidic but less so (pH ~3.5)
→ Lemon juice is more acidic → more

- Sea water = slightly basic (pH ~8.1)
- Baking soda solution = more basic (pH ~8.3–9)
→ Sea water is less basic → less

- Bleach = very basic (pH ~12.5)
- Ammonia = basic but less than bleach (pH ~11.5)
→ Bleach is more basic → more

- Gastric acid = pH ~1.5
- Lemon juice = pH ~2
→ Gastric acid is more acidic → more

- Orange juice = pH ~3.5
- Lemon juice = pH ~2 → lemon is more acidic
→ So orange juice is less acidic than lemon juice → less

- Baking soda = pH ~8.3
- Soapy water = pH ~9–10? Wait — actually, soap can be around 9–10, baking soda is about 8.3 → so baking soda is less basic than soapy water? Let me check standard values:

Actually, typical values:
- Baking soda (sodium bicarbonate) solution: pH ~8.3
- Soapy water: depends, but often pH 9–10
→ So baking soda is less basic → less

Wait — question 25: “Baking soda is (more or less) basic than soapy water.”

If soapy water is more basic, then baking soda is less basic → less

But some sources say soap can be pH 9–10, baking soda 8.3 → yes, so baking soda is less basic.

However, sometimes people confuse — let’s stick with standard science:

Standard comparison:

Acidity order (most to least acidic):
Gastric acid > lemon juice > orange juice > black coffee > urine > sea water > milk of magnesia > baking soda > soapy water > ammonia > bleach? No — wait, bleach is strongest base.

Actually, bases from weakest to strongest:
Milk of Magnesia < baking soda < soapy water < ammonia < bleach

So:

16. Gastric acid vs urine → gastric acid is more acidic → more

17. Milk of Magnesia vs bleach → MoM is less basic → less

18. Soapy water vs ammonia → soapy water is less basic → less

19. Black coffee vs orange juice → coffee is less acidic → less

20. Lemon juice vs orange juice → lemon is more acidic → more

21. Sea water vs baking soda → sea water is less basic → less

22. Bleach vs ammonia → bleach is more basic → more

23. Gastric acid vs lemon juice → gastric acid is more acidic → more

24. Orange juice vs lemon juice → orange juice is less acidic → less

25. Baking soda vs soapy water → baking soda is less basic → less

Wait — I think I have a mistake on #25.

Let me verify pH values quickly (standard approximations):

- Baking soda (NaHCO₃) solution: pH ≈ 8.3
- Soapy water: typically pH 9–10 (depending on soap)
→ So baking soda is less basic → answer is less

Yes.

Final Answers for Part 2:

16. more
17. less
18. less
19. less
20. more
21. less
22. more
23. more
24. less
25. less

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Final Answer:

Matching:
1-M, 2-H, 3-D, 4-I, 5-O, 6-E, 7-B, 8-L, 9-J, 10-C, 11-G, 12-N, 13-F, 14-A, 15-K

Comparisons:
16. more
17. less
18. less
19. less
20. more
21. less
22. more
23. more
24. less
25. less