Two students decided to investigate the effect of water and air on iron objects under identical experimental conditions. They measured the mass of each object before placing it partially immersed in 10 ml of water. After a few days, the object was removed and dried and their masses were measured. The table shows their results. Student Object Mass of Object before Rusting in g Mass of the object coated object in g A Nail 3 . 0 3 . 15 B Thin Plate 6 . 0 6 . 33 a) What might be the reason for the varied observations of the two students? (b) In another set up the students coated iron nails with zinc metal and noted that, iron nails coated with zinc prevents rusting. They also observed that zinc initially acts as a physical barrier, but an extra advantage of using zinc is that it continues to prevent rusting even if the layer of zinc is damaged. Name this process of rust prevention and give any two other methods to prevent rusting.

a) When iron objects are exposed to air and moisture, it undergoes rusting. In this case two students measuring the effect of air and water on the iron objects. Student A took an iron nail and student B has taken the thin plate. In this experiment both have immersed their respective iron objects as half of the portion of an iron object was immersed in water, whereas the other portion of the object was exposed to air. After few days the iron objects of respective student A and student B, where weighed. The results showed of the iron nails and thin plate eventually increased than their actual weight by 3 . 0 to 3 . 15 and 6 . 0 to 6 . 33 . So we can clearly see that the weight of thin plate was more increased than the iron nail because as we can see the surface area of thin plate was more exposed to the water and air compared to the iron nail. So we can conclude that as the surface area of iron objects increase, increases the rusting. b) We can prevent rusting by coating zinc over iron objects. This process is known as galvanisation. Zinc is more reactive than iron, initially, zinc physically acts as a barrier to iron, but later zinc will react with air and form an oxide layer, that will also protect iron objects. We can prevent rusting by painting iron objects. Greasing is also one of the methods by which we can prevent rusting.

In which of the following application of iron, rusting will occur most? Support your answer with valid reason. A - Iron Bucket electroplated with Zinc B - Electricity cables having iron wires covered with aluminium C - Iron hinges on a gate D - Painted iron fence

Iron rusts when it comes in direct contact with air and water. Rusting is an oxidation reaction. The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust. Coating of other metals such as zinc, aluminium or chromium, oiling or greasing, painting and alloying are methods used to prevent or slow down the process of rusting. Hence, as A- An iron bucket is electroplated with zinc it will not get rust easily. B- Electricity cables having iron wires covered with aluminium it will also protect from rust. And D - painted iron fence, also has a protected covering to prevent from rust. But, C - Iron hinges on a gate which are in contact with both the atmospheric oxygen and moisture or water vapour are likely to rust easily.

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10th Uttar Pradesh Board

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Science Crash Course (Based on Revised Syllabus-2023)>Chapter 14 - Sample Paper 1>Exercise>Q 29

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Identify the type of reaction mentioned above in (i) and (ii). Give one example for each type in the form of a balanced chemical equation.

MEDIUM

10th Uttar Pradesh Board

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Science Crash Course (Based on Revised Syllabus-2023)>Chapter 14 - Sample Paper 1>Exercise>Q 40

What is the role of concentrated sulphuric acid, when it is heated with ethanol at $443 K$ ? Give the reaction evolved.

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10th Uttar Pradesh Board

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Science Crash Course (Based on Revised Syllabus-2023)>Chapter 14 - Sample Paper 1>Exercise>Q 41

Reshu by mistake forgot to label the two test tubes containing Ethanol and Ethanoic acid. Suggest an experiment to identify the substances correctly? Illustrate the reactions with the help of chemical equations

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10th Uttar Pradesh Board

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Science Crash Course (Based on Revised Syllabus-2023)>Chapter 14 - Sample Paper 1>Exercise>Q 43

Sexual maturation of reproductive tissues and organs are necessary link for reproduction. Elucidate.

MEDIUM

10th Uttar Pradesh Board

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Science Crash Course (Based on Revised Syllabus-2023)>Chapter 14 - Sample Paper 1>Exercise>Q 44

How are variations useful for species if there is drastic alteration in the niches?

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10th Uttar Pradesh Board

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Science Crash Course (Based on Revised Syllabus-2023)>Chapter 14 - Sample Paper 1>Exercise>Q 45

Explain how the uterus and placenta provide the necessary conditions for proper growth and development of the embryo after implantation.

MEDIUM

10th Uttar Pradesh Board

IMPORTANT

Science Crash Course (Based on Revised Syllabus-2023)>Chapter 14 - Sample Paper 1>Exercise>Q 47

Two students decided to investigate the effect of water and air on iron objects under identical experimental conditions. They measured the mass of each object before placing it partially immersed in 10 ml of water. After a few days, the object was removed and dried and their masses were measured. The table shows their results.

Student	Object	Mass of Object before Rusting in g	Mass of the object coated object in g
A	Nail	$3.0$	$3.15$
B	Thin Plate	$6.0$	$6.33$

a) What might be the reason for the varied observations of the two students?
(b) In another set up the students coated iron nails with zinc metal and noted that, iron nails coated with zinc prevents rusting. They also observed that zinc initially acts as a physical barrier, but an extra advantage of using zinc is that it continues to prevent rusting even if the layer of zinc is damaged. Name this process of rust prevention and give any two other methods to prevent rusting.

HARD

10th Uttar Pradesh Board

IMPORTANT

Science Crash Course (Based on Revised Syllabus-2023)>Chapter 14 - Sample Paper 1>Exercise>Q 48

In which of the following application of iron, rusting will occur most? Support your answer with valid reason.

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A - Iron Bucket electroplated with Zinc

B - Electricity cables having iron wires covered with aluminium

C - Iron hinges on a gate

D - Painted iron fence

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