Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 631 · 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 battery cell is not needed for the secret lemon message. (a) True (b) False
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) lemon juice (d) a balloon
3. 3.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) reading the message (d) plugging in the iron
4. 4.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) writing the message
5. 5.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
6. 6.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) rub your eyes (d) wash your hands
7. 7.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it is cold (d) it can burn skin
8. 8.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) chemical (d) musical
9. 9.🧺 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) lemon juice
10. 10.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) how dark the writing is (d) the iron setting
13. 13.True or false: reading the message is a job a child can do. (a) True (b) False
14. 14.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
15. 15.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
17. 17.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
18. 18.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
19. 19.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
20. 20.⚖️ 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
21. 21.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) plugging in the iron (c) cutting the lemon (d) putting the iron away
22. 22.⚖️ 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 same cotton bud (c) how dark the writing is (d) the iron setting
23. 23.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
24. 24.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) ironing the paper
25. 25.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) plugging in the iron (d) dipping the cotton bud
26. 26.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) writing the message (d) letting the paper dry
27. 27.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
28. 28.⚖️ 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
29. 29.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) white paper (d) a balloon
30. 30.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
31. 31.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
32. 32.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) whoever is fastest (d) only an adult
33. 33.🔮 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
34. 34.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
35. 35.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) ironing the paper (c) putting the iron away (d) plugging in the iron
36. 36.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the paper ate it (c) the ink is magnetic (d) it turned into air
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same cotton bud
38. 38.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) almost nothing (d) blue words
39. 39.True or false: letting the paper dry is a job for an adult. (a) True (b) False
40. 40.⚖️ 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

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