Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 880 · 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.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is sticky (d) it is magnetic
2. 2.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
3. 3.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
4. 4.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) putting the iron away
5. 5.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
6. 6.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a mirror (c) a magnet (d) a balloon
7. 7.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) reading the message (d) putting the iron away
8. 8.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
9. 9.⚖️ 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
10. 10.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) rub your eyes (d) lick your fingers
11. 11.True or false: cutting the lemon is a job for an adult. (a) False (b) True
12. 12.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) putting the iron away (d) writing the message
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) an adult with an iron (d) a mirror
14. 14.True or false: yeast is needed for the secret lemon message. (a) False (b) True
15. 15.⚖️ 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
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) white paper (d) an adult with an iron
17. 17.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we measure it (c) we keep it the same
19. 19.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) ironing the paper (d) dipping the cotton bud
20. 20.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
21. 21.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a cotton bud (d) yeast
23. 23.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
24. 24.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
25. 25.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
26. 26.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) an adult with an iron (c) lemon juice (d) a small bowl
28. 28.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
29. 29.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if cooled (d) yes, if shaken
30. 30.⚖️ 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
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) how dark the writing is (c) the same cotton bud (d) the same paper
32. 32.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) white (d) brown
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the same paper (c) the kind of juice (d) how dark the writing is
34. 34.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
35. 35.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
36. 36.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
37. 37.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) letting the paper dry (d) ironing the paper
38. 38.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) any child (d) whoever is fastest
39. 39.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) writing the message
40. 40.⚖️ 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

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