Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 233 · 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 ironing time (b) the same paper (c) the iron setting (d) how dark the writing is
2. 2.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) lemon juice (d) a battery cell
4. 4.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) an adult with an iron (d) a cotton bud
6. 6.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) blue words (d) almost nothing
7. 7.⚖️ 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 same paper (c) the same cotton bud (d) the kind of juice
8. 8.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) ironing the paper
9. 9.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) ironing the paper (d) writing the message
10. 10.⚖️ 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
11. 11.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
12. 12.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) white (d) green
13. 13.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
14. 14.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) it turned into air (d) the paper ate it
16. 16.⚖️ 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) False (b) True
17. 17.True or false: plugging in the iron is a job for an adult. (a) False (b) True
18. 18.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
19. 19.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) cutting the lemon (d) plugging in the iron
20. 20.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) reading the message (d) letting the paper dry
21. 21.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
22. 22.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
23. 23.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
24. 24.⚖️ 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
25. 25.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) writing the message
26. 26.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
27. 27.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
28. 28.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) no, it stays brown (d) yes, if cooled
29. 29.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a balloon (c) a magnet (d) turmeric powder
30. 30.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) reading the message
31. 31.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
32. 32.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
33. 33.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
34. 34.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) physical (d) musical
35. 35.True or false: writing the message is a job for an adult. (a) True (b) False
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
37. 37.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
38. 38.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
39. 39.🧺 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) yeast (d) lemon juice
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True

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