Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 416 · 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 iron setting is kept the same. (a) False (b) True
2. 2.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) a balloon (d) a magnet
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
4. 4.🔮 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
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) True (b) False
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a magnet (d) a small bowl
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a balloon (d) lemon juice
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a balloon (d) lemon juice
9. 9.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
10. 10.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) green (d) brown
11. 11.⚖️ 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) False (b) True
12. 12.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
13. 13.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) the youngest child (d) any child
14. 14.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) ironing the paper (d) dipping the cotton bud
15. 15.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) lemon juice (c) a small bowl (d) a cotton bud
17. 17.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) physical (d) magnetic
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) yeast (d) lemon juice
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) lemon juice (d) a mirror
21. 21.True or false: reading the message is a job a child can do. (a) False (b) True
22. 22.⚖️ 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
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) yeast (d) white paper
24. 24.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
25. 25.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) reading the message (d) putting the iron away
26. 26.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) plugging in the iron (d) letting the paper dry
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
28. 28.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) dipping the cotton bud (d) ironing the paper
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a battery cell (d) white paper
30. 30.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) writing the message (d) plugging in the iron
31. 31.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
32. 32.⚖️ 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
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a magnet (c) white paper (d) an adult with an iron
34. 34.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
35. 35.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
36. 36.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
38. 38.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) cutting the lemon (d) writing the message
39. 39.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) white paper (c) turmeric powder (d) a mirror
40. 40.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, in the dark (d) yes, if cooled

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