Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 291 · 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.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) lick your fingers (d) skip washing
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) a cotton bud (d) white paper
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the kind of juice (c) the same paper (d) the same cotton bud
4. 4.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
5. 5.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) brown (d) white
8. 8.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
9. 9.True or false: white paper is needed for the secret lemon message. (a) True (b) False
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
11. 11.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the iron setting (c) how dark the writing is
13. 13.True or false: letting the paper dry is a job a child can do. (a) True (b) False
14. 14.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, if shaken (d) yes, in the dark
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
16. 16.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
17. 17.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) an adult with an iron (c) a cotton bud (d) white paper
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a magnet (c) white paper (d) lemon juice
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) a small bowl (d) an adult with an iron
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) turmeric powder (c) a cotton bud (d) white paper
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
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) True (b) False
23. 23.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) how dark the writing is (c) the same paper
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) white paper (c) lemon juice (d) an adult with an iron
26. 26.True or false: ironing the paper is a job a child can do. (a) True (b) False
27. 27.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) plugging in the iron (d) putting the iron away
28. 28.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
30. 30.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) writing the message (d) ironing the paper
31. 31.True or false: yeast is needed for the secret lemon message. (a) True (b) False
32. 32.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
33. 33.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) cutting the lemon (d) putting the iron away
34. 34.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) white paper (d) a mirror
36. 36.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) an adult with an iron (c) a mirror (d) a battery cell
37. 37.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a small bowl (c) a balloon (d) a battery cell
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) True (b) False
39. 39.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
40. 40.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through

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