Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 596 · 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? Which of these is what we measure? (a) the same cotton bud (b) the iron setting (c) the ironing time (d) how dark the writing is
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
3. 3.True or false: yeast is needed for the secret lemon message. (a) False (b) True
4. 4.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) plugging in the iron (d) reading the message
5. 5.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) white paper (d) turmeric powder
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
8. 8.⚖️ 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 same cotton bud (c) how dark the writing is
9. 9.⚖️ 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) True (b) False
10. 10.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
11. 11.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) skip washing (d) lick your fingers
12. 12.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) writing the message (c) cutting the lemon (d) ironing the paper
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) an adult with an iron (d) a magnet
14. 14.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
15. 15.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
16. 16.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) putting the iron away (d) plugging in the iron
17. 17.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) turmeric powder (d) white paper
19. 19.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
20. 20.⚖️ 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 change it (c) we measure it
21. 21.True or false: white paper is needed for the secret lemon message. (a) False (b) True
22. 22.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) a magnet (d) white paper
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
25. 25.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) dipping the cotton bud (d) ironing the paper
26. 26.True or false: writing the message is a job for an adult. (a) False (b) True
27. 27.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a battery cell (d) lemon juice
29. 29.🍋 Which of these steps is a job a child can do? (a) reading the message (b) cutting the lemon (c) putting the iron away (d) ironing the paper
30. 30.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
31. 31.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
32. 32.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a magnet (c) a balloon (d) turmeric powder
33. 33.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
35. 35.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) putting the iron away (d) reading the message
36. 36.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
37. 37.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
38. 38.⚖️ 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 iron setting (c) the kind of juice (d) the ironing time
39. 39.True or false: ironing the paper is a job for an adult. (a) False (b) True
40. 40.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False

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