Science 2009 CBSE [ Delhi ] Set I
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Q1
Fresh milk has a pH of 6. When it changes into curd (yogurt) will its pH value increase or decrease? Why?
Marks:1View AnswerAnswer:
When milk is changed into curd, its pH value decreases due to the increase in the concentration of lactic acid.
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Q2
Draw the given diagram in your answer book and complete it for the path of ray of light beyond the lens.
Marks:1View AnswerAnswer:
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Q3
Name two tissues that provide control and coordination in multicellular animals.
Marks:1View AnswerAnswer:
Nervous tissue and Muscular tissue are the two tissues that provide control and coordination in multicellular animals.
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Q4
Name a reducing agent that may be used to obtain manganese from manganese dioxide.
Marks:1View AnswerAnswer:
Sodium, being more reactive than manganese, can be used to reduce manganese from manganese dioxide.
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Q5
Balance the following chemical equation:
Marks:1View AnswerAnswer:
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Q6
Why does sky look blue on a clear day?
Marks:1View AnswerAnswer:
The sky appears blue on a clear day because air scatters short-wavelength light more than longer wavelengths. So, blue light is of short wavelength present at the end of the visible spectrum, and is more strongly scattered in the atmosphere than long wavelength red light.
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Q7
Why does a ray of light bend when it travels from one medium into another?
Marks:1View AnswerAnswer:
The speed of light is different in different media. When the ray of light travels from one medium into another it bends because the speed of the light changes.
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Q8
What will happen to a plant if its xylem is removed?
Marks:1View AnswerAnswer:
Water will not be transported from roots to other parts.
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Q9
What are the two main components of our environment?
Marks:1View AnswerAnswer:
Biotic (living organisms) and abiotic( non-living) components.
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Q10
What are natural resources? State two factors that work against an equitable distribution of these resources.
Marks:2View AnswerAnswer:
Natural resources are defined as resources that are naturally present in the environment and that can be used for human development and welfare. The two factors that work against an equitable distribution of these resources are:
1. Variation in economical conditions.
2. Geographical variation.
