Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 617 · 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.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) a battery cell (d) white paper
2. 2.⚖️ 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 iron setting
3. 3.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) putting the iron away
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) an adult with an iron (d) a magnet
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a balloon (d) a cotton bud
6. 6.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) writing the message (d) ironing the paper
7. 7.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) lick your fingers (d) skip washing
8. 8.True or false: letting the paper dry is a job a child can do. (a) True (b) False
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) yeast (c) lemon juice (d) white paper
10. 10.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) blue words (d) dark brown words
11. 11.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
12. 12.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) the kind of juice (c) how dark the writing is
14. 14.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, in the dark (d) yes, if shaken
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the kind of juice (c) the same paper (d) the same cotton bud
16. 16.⚖️ 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
17. 17.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is cold (d) it is magnetic
18. 18.⚖️ 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
19. 19.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
20. 20.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
21. 21.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
22. 22.⚖️ 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
23. 23.True or false: writing the message is a job for an adult. (a) True (b) False
24. 24.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is
26. 26.🔮 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
27. 27.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
28. 28.True or false: reading the message is a job for an adult. (a) False (b) True
29. 29.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) white paper (d) a magnet
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
34. 34.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
35. 35.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a mirror (c) yeast (d) a small bowl
36. 36.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) dipping the cotton bud (d) cutting the lemon
37. 37.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
38. 38.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) plugging in the iron (d) cutting the lemon
39. 39.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) physical (d) musical
40. 40.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True

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