Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 24 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
3. 3.True or false: putting the iron away is a job a child can do. (a) False (b) True
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a mirror (c) a small bowl (d) an adult with an iron
5. 5.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) no, it stays brown (d) yes, if cooled
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the ironing time (c) the same paper (d) the same cotton bud
7. 7.True or false: ironing the paper is a job for an adult. (a) True (b) False
8. 8.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) plugging in the iron
9. 9.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is magnetic (d) it is sticky
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a balloon (d) white paper
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
12. 12.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) heat adds colour (d) paper turns lemony
13. 13.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
14. 14.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
15. 15.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) magnetic (d) physical
16. 16.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
17. 17.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) a balloon (d) a small bowl
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False
20. 20.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
21. 21.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) writing the message (d) plugging in the iron
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a magnet (d) a small bowl
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a battery cell (c) a cotton bud (d) a small bowl
25. 25.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
26. 26.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) putting the iron away (d) letting the paper dry
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
28. 28.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) it gets darker (d) writing stays faint
29. 29.True or false: reading the message is a job a child can do. (a) True (b) False
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) turmeric powder (d) an adult with an iron
32. 32.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
34. 34.True or false: white paper is needed for the secret lemon message. (a) True (b) False
35. 35.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) reading the message
36. 36.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) lemon juice (d) a battery cell
37. 37.True or false: plugging in the iron is a job a child can do. (a) True (b) False
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the kind of juice (c) the iron setting (d) the same cotton bud
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
40. 40.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed

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