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Give reasons for the following: (i) Most metals conduct electricity well. (ii) The reaction of iron (III) oxide [Fe2O3] with heated aluminium is used to join cracked machine parts.

(i) The outer electrons of metal atoms are not tied to any one atom. Therefore, these electrons are free to move within the structure of metal... View Article

List in tabular form three chemical properties on the basis of which we can differentiate between a metal and a non-metal.

METALS NON- METALS They react with oxygen to form basic oxides. 2Mg + O2 → 2MgO They react with oxygen to form acidic or neutral... View Article

What is water harvesting? List two main advantages associated with water harvesting at the community level. Write two causes for the failure of sustained availability of groundwater.

Rainwater harvesting is the simple process or technology used to conserve Rainwater by collecting, storing, conveying and purifying of Rainwater... View Article

Define an ecosystem. Draw a block diagram to show the flow of energy in an ecosystem

The ecosystem is a self-contained unit of living things(plants, animals, and decomposers), and their nonliving environment (soil, air, and... View Article

What is a rainbow? Draw a labelled diagram to show the formation of a rainbow.

The rainbow is an arch of seven colours (violet, indigo, blue, green, yellow, orange, and red) visible in the sky. When the sun is shining and... View Article

Name the plant Mendel used for his experiment. What type progeny was obtained by Mendel in F1 and F2 generations when he crossed with tall short plants? Write the ratio he obtained in F2 generation plants.

The plant that Mendel used was the pea plant. Mendel crossed a tall and a short pea plant. The progeny he obtained were all tall. This was the F1... View Article

What are plant hormones? Name the plant hormones responsible for the following: (i) Growth of stem (ii) Promotion of cell division (iii) Inhibition of growth

Plant hormones are the chemicals or hormones that perform the function of control and coordination in plants. They are present in very low... View Article

Trace the sequence of events that occur when a bright light is focused on your eyes.

When a bright light is focused on our eye, the receptor cell receives the message and passes it on to the sensory neuron, then it goes to the... View Article

Write three types of blood vessels. Give one important feature of each.

The three types of blood vessels are: Arteries carry oxygen-rich blood away from the heart to all of the body's tissues. Arteries branch... View Article

Based on the group valency of elements state the formula for the following giving justification for each: (i) Oxides of 1st group elements. (ii) Halides of the elements of group 13. (iii) Compounds formed when an element of group 2 combines with an element of group seventeen.

Based on the group valency of elements states the formula are: (1) Let the elements of the first group is A and let its oxide be denoted by 'O'.... View Article

Identify the acid and the base from which sodium chloride is obtained. Which type of salt is it? When is it called rock salt? How is rock salt formed?

Acid: Hydrochloric acid Base: Sodium hydroxide Sodium chloride is a neutral salt. It is known as rock salt in crystalline form. It is the result... View Article

Identify the type of reactions taking place in each of the following cases and write the balanced chemical equation for the reactions. (a) Zinc reacts with silver nitrate to produce zinc nitrate and silver. (b) Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead iodide.

(a) Zinc reacts with silver nitrate to produce zinc nitrate and silver. Zn(s) + AgNO3(aq) → Zn(NO3)2(aq) + 2Ag(s) It is a displacement reaction.... View Article

2g of silver chloride is taken in a china dish and the china dish is placed in sunlight for some time. What will be your observation in this case? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction.

Silver chloride is a light-sensitive compound i.e. it reacts in presence of light. When silver chloride is exposed to sunlight, being light... View Article

Define the term power of accommodation. Write the modification in the curvature of the eye lens which enables us to see the nearby objects clearly?

The term 'power of accommodation' refers to the ability of the eye to focus the distant objects as well as the nearby objects on the retina by... View Article

Write two different ways in which glucose is oxidized to provide energy in the human body. Write the products formed in each case.

The different ways in which glucose is oxidized to provide energy in various organisms are Aerobic respiration Anaerobic respiration The... View Article

The electronic configuration of an element is 2, 8, 4. State its: (a) group and period in the Modern Periodic Table. (b) name and write its one physical property.

The given element’s electronic configuration is 2, 8, 4. This means that there are 14 electrons in this element. (a) The element belongs to the... View Article

How it can be proved that the basic structure of the Modem Periodic Table is based on the electronic configuration of atoms of different elements?

The modern periodic table was given by Henry Mosely. The modern periodic law states that the periodicity of elements is a function of their... View Article

Why is biogas considered excellent fuel?

Biogas is considered an excellent fuel because it is a clean fuel (smoke-free) with a high calorific value. Its burning does not emit harmful... View Article

What is the function of a Galvanometer in a circuit?

The function of a galvanometer in a circuit is to detect or measure the presence of a small amount of current flowing in a circuit. A... View Article

A person suffering from myopia (near-sightedness) was advised to wear corrective lens of power – 2·5 D. A spherical lens of same focal length was taken in the laboratory. Draw a ray diagram to show the position and nature of the image formed at a distance of 10 cm from the lens

As the power of the lens is −ve, the lens used is concave/diverging. The position of the image is on the same side as that of the object (on the... View Article

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