Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 422 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
2. 2.True or false: cutting the lemon is a job for an adult. (a) False (b) True
3. 3.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) letting the paper dry (c) putting the iron away (d) cutting the lemon
4. 4.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) cutting the lemon (d) writing the message
5. 5.⚖️ 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) False (b) True
6. 6.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
7. 7.True or false: reading the message is a job a child can do. (a) False (b) True
8. 8.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
9. 9.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) putting the iron away
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) a small bowl (d) turmeric powder
11. 11.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) how dark the writing is (c) the kind of juice (d) the iron setting
13. 13.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) white (d) brown
14. 14.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
15. 15.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) lemon juice (c) an adult with an iron (d) a small bowl
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
18. 18.⚖️ 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
19. 19.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) dipping the cotton bud
20. 20.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) musical (d) magnetic
21. 21.🧺 Which of these is not needed for the secret lemon message? (a) turmeric powder (b) lemon juice (c) white paper (d) a cotton bud
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
23. 23.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
24. 24.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) letting the paper dry
25. 25.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) lick your fingers (d) wash your hands
26. 26.True or false: putting the iron away is a job a child can do. (a) True (b) False
27. 27.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the ink is magnetic (d) the paper ate it
28. 28.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) reading the message
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a balloon (d) an adult with an iron
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a balloon (d) a cotton bud
31. 31.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
32. 32.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
34. 34.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
35. 35.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
36. 36.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
37. 37.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
39. 39.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
40. 40.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a battery cell (c) an adult with an iron (d) yeast

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