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The size of an ostrich egg is 170 mm × 130 mm. It is the largest cell. It is a single cell called “fertilized egg cell” or “zygote”.

The various parts of the cell are colorless and hence, difficult to distinguish. So, various stains are used to colour the parts of the cell to study the detailed structure through a microscope.

The dyes (stains ) which are used in the study of cell structure are methylene blue, dilute iodine solution, etc.

Nucleus is the largest floating body generally in the centre of a cell. It is the control centre of the cell and is a membrane bound organelle found in eukaryotic cell. The nucleus contains DNA with histones that form the chromosome.

Nucleus is the largest floating body generally in the center of a cell.

D. ostrich 

The largest cell measuring 170 mm ×130 mm, is the egg of an ostrich.

C. A and C 

Cell wall is a characteristics of plant cell only and absent in animal cell. It is an outer, rigid, protective and supportive covering of plant cells. The cell wall lies outside of the plasma membrane. Epidermal cell and mesophyll cell are examples of plant cells. Thus, they have cell wall.

Plant and animal specimens are usually stained with dyes before observing them because they are transparent and will not be visible to naked eye. Hence, they are stained and then observed under a microscope, staining makes them clearly visible. Animal cells are stained with methylene blue and plant cells are stained with iodine.

B. red blood cell 

Red blood cell does not have a nucleus.

Few additional features of plant cell are that they possess cell wall and have chloroplast, which are not found in animal cells. Both, animal and plant cells have nucleus, cytoplasm, plasma membrane, Golgi apparatus, mitochondria, endoplasmic reticulum and ribosomes.

Yes, all organisms have a cell membrane. It is one of the basic component of cell that encloses the other basic components-cytoplasm and nucleus. The cell membrane separates the cells from one another and controls the movement of materials in and out of the cell. Both plant and animals have cell membrane. In plants it is inside the cell wall and in animals it is the outer layer of the cell.

The organisms made up of many cells are called multicellular organisms. 

Examples: Animal and plant.

The organisms made up of single cell are called unicellular organisms. 

Examples: Amoeba, Paramecium.

A. A and B 

An amoeba cell and white blood cell present in human blood can change their shape.

Dialysis is the artificial method of removal of wastes from the blood. 

Dr. William Kolff a Dutch physician in the year 1947 constructed dialysis machine. 

Dialysis machine works on principle of diffusion and filtration across a semi permeable membrane.

Osmosis is the principle involved in dialysis and reverse osmosis.

C) A is true but R is false

(d) Bakelite

(a) Melamine

(d) polyester and cotton

(b) I-(iii), II-(i), III-(ii) 

The characteristics of the particles of matter are:

(1) Particles of matter have space between them:

All matter consists of particles which have space between them. Hence when two different substances are mixed, the particles of one substance get into the spaces between particles of the other. The intermixing of particles of two different types of matter on their own is called diffusion.

(2) Particles of matter attract each other: 

The particles of matter are held together by forces of attraction. These inter-molecular forces of attraction are responsible for the physical and chemical nature of the substance.

The strength of the force of attraction between particles of matter increase in the order:

Gases<Liquids<solids

(a) When gas is stored in a container, the fast moving particles of the gas collides with each other thus exerts pressure on the walls of container 

(b) They have high kinetic energy and negligible force of attraction so it can move constantly moving with high speed in all directions 

(c) Gases are easily compressible as they have large inter-molecular spaces. The gas particles can come closer when external pressure is applied on gases.

(a) Diffusion: 

(i)Matter is made up of tiny particles 

(ii)The particles of matter are constantly moving. 

(b) Brownian motion: 

(i) The particles of matter is very small. 

(ii) The particles of matter are constantly moving.

(a) Matter is anything that occupies and has mass. Wood, air, water are the examples for matter. 

(b)1. Matter is made up of tiny particles 

2. The particles of mater attract each other. 

3. The particles of matter have spaces between them.

4. The particles of matter are constantly moving.

Air, water, exhaust from chimneys, chalk, cotton, honey, iron.

The price of anything depends on how much of it is available and how essential it is. Both coal and petroleum are exhaustible resources but we need them, both as fuel and as starting material for synthesising new compounds. Since supply is limited and becoming more expensive as the demand for petrol increase.

Bitumen, a petroleum product, is used in place of coal-tar for metalling the roads.

Engine must be stopped in the traffic signals or in heavy traffic.

1. Temperature is less,

2. Pressure is low.

The SI unit of pressure is Pascal (Pa). 

Its value in 1 atmospheric pressure is: 

1 atmosphere (atm) = 1.01 × 10⁵ Pa 

Note: Atmospheric pressure is the pressure of air in the atmosphere. The atmospheric pressure at sea level is 1 atm.

We should use fossil fuels only when absolutely necessary because fossil fuels are non-renewable (exhaustible) source of energy. As we know that non-renewable resources are those resources whose amount in nature is limited. We have to save them now for our coming future generation and use them only when absolutely necessary.

(d) dead remains of living organisms.

Coal tar is the source from which naphthalene balls are obtained. Coal tar is a
black thick oily liquid with bad smell. Products made from coal tar are used as starting materials for making objects used in everyday life. Naphthalene balls are used to repel insects.

Naphthalene balls used to repel moths and other insects are obtained from coal tar.

L.P.G. which is used for cooking. In the cylinder petrol is in liquid form. When it is lighted it becomes gas.

We can save petrol/diesel while driving by following the tips given below:

• Drive at a normal speed.
• Switch off the engine at traffic lights or at a place where we have to wait.
• Ensure proper maintenance of the vehicle.
• Check tyre pressure regularly before driving.

Sublimation is a change of state directly from solid to gas without changing to liquid state or vice versa. Hence, the given statement is completely wrong.

Biodiesel is one of the biofuel. Which is not toxic and renewable. It is made from the biological ingredients instead of petroleum or crude oil. Biodiesel usually made from the plant oils or animal fat through a series of chemical reactions.

It is used in diesel engines.

Because at 0°C (273 K) particles of water have more energy comparing it to water at the same temperature.

Particles in a solid move farther apart on heating - A metal rod expands on heating, when we increase the temperature. The kinetic energy of the particles increases. As a result, the particles leave their fixed positions and start moving freely. 

Different particles of different elements have different masses. A gold bracelet (has large mass and density) is much heavier than an identical silver bracelet (has lower density and mass). 

Gas particles always spread out to ill the space available to them. For example: It is easier to squash a balloon filled with air than a balloon filled with water. 

Gas particles are father apart than liquid particles. For example: You can smell dinner cooking in the kitchen when you are in your bedroom.

Yes, I will agree with the statement. CNG and LPG are completely combustible. CNG is less polluting and it is cleaner fuel releasing small quantity of harmful gases. Similarly LPG is also releases few polluting gases. CNG and LPG does not release hydrocarbons. They only release carbon dioxide and small quantities of sulphur dioxide and nitrous oxide. So using CNG and LPG as fuels for automobiles help us to minimize air pollution and maintains ecological balance.

Biodiversity affected by excessive use of fossil fuels:

1. Burning fuels releases carbon dioxide a green house gas, which causes climate changes and leads to global warming. 

2. Coal fired power plants emits mercury, selenium, arsenic, lead in addition to green house gases which is harmful to human health and environment. 

3. Many paints made from petroleum and heavy metals release toxic products into air. These toxic products cause a variety of health problems including heart, lungs damage, nausea and dizziness. So these are harmful effects of excessive use of fossil fuels on biodiversity.

Fossil fuels are formed from the dead remains of living organisms under the earth over millions of years

(d) wild life and minerals

(c) limited in quantity. 

Correct option is A) Candle

Correct option is C) mercury