Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 544 · 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: white paper is not needed for the secret lemon message. (a) False (b) True
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) an adult with an iron (d) turmeric powder
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) ironing the paper (c) reading the message (d) letting the paper dry
5. 5.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
6. 6.⚖️ 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) False (b) True
7. 7.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
9. 9.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) reading the message (c) cutting the lemon (d) putting the iron away
10. 10.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
11. 11.True or false: writing the message is a job for an adult. (a) True (b) False
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) how dark the writing is (c) the iron setting (d) the same cotton bud
13. 13.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
14. 14.⚖️ 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 keep it the same (c) we measure it
15. 15.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) dipping the cotton bud (d) writing the message
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a balloon (c) lemon juice (d) a small bowl
17. 17.🍋 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
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a mirror (d) lemon juice
19. 19.⚖️ 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 ironing time (c) the same paper (d) the same cotton bud
20. 20.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
21. 21.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) letting the paper dry (d) cutting the lemon
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
23. 23.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) letting the paper dry
24. 24.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
25. 25.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) ironing the paper (d) writing the message
26. 26.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) an adult with an iron (d) a magnet
28. 28.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
30. 30.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it can burn skin (d) it is magnetic
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
32. 32.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) dipping the cotton bud
33. 33.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
34. 34.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
35. 35.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
36. 36.⚖️ 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
37. 37.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) only an adult (d) the youngest child
38. 38.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
39. 39.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) almost nothing (d) a rainbow
40. 40.True or false: plugging in the iron is a job for an adult. (a) False (b) True

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