An atom is defined as the smallest unit of matter indivisible by chemical means.

Physical change is reversible and no new substance is formed.

All the options except melting of ice are chemical change because new substances are formed and the process is also not reversible.

For the melting of ice, it can be frozen into ice again so it is reversible and the substance is still water in different forms.

The kidneys' primary function is to filter blood. They also remove waste and balance the body's fluids.

Process of the working of an electric bell

1. The switch is pressed and current flows through the circuit.
2. The electromagnet is powered and generates a magnetic field that attracts the iron strip towards it.
3. The striker strikes the gong (bell).
4. When the striking arm strikes the gong, the contact is broken and the current stops flowing through the circuit.
5. This causes the electromagnet to lose its magnetic field.
6. The connected spring arm returns the striker to its original rest position.
7. The contact is restored and current flows through the circuit (provided the main switch is still pressed).

Characteristics of mammals

1. Mammals are warm-blooded animals who give birth to their younger ones.
2. They are the most dominant form of animals found in almost all types of habitats.
3. They have mammary glands that help them produce milk to feed their younger ones
4. Presence of region of the brain known as Neocortex
5. Their skin possesses oil glands (sebaceous glands) and sweat glands (sudoriferous glands).
6. The fur of hair throughout the body which helps animals adapt to their environment.
7. They are heterodont, i.e., possess different types of teeth.
8. Mammals also possess cervical vertebrae.
9. The skull is dicondylic.
10. The trunk is divided into thorax and abdomen.
11. The mammals respire through lungs.
12. Good sense of hearing as mammals are aided with 3 middle ear bones
13. Mammals have a four-chambered heart. The sinus venous and renal portal system are absent.
14. Presence of single-boned lower jaws.
15. The brain is well developed divided into cerebrum, cerebellum and medulla.
16. They possess 12 pairs of cranial nerves.
17. Exhibit one of the most advanced forms of Diaphragms.
18. The mammals can lay eggs also. They are known as viviparous.

Schistosomiasis, also known as bilharzia, is an infection caused by a parasitic worm that lives in fresh water in subtropical and tropical regions.

Kelvin = 273 + Degree Celsius

Degree Celsius = 20

Kelvin = 273 + 20 = 293 K

Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism. The remaining 97–99.5% is lost by transpiration

Reflex action is a sudden and involuntary response to stimuli. It helps organisms to quickly adapt to an adverse circumstance that could have the potential to cause bodily harm or even death. Pulling our hands away immediately after touching a hot or cold object is a classic example of a reflex action.

Chemical Equation

CaCO₃(s) + 2HCl(aq) → CaCl₂ (s) + H₂O(aq) + CO₂(g)

CO₂(g) = Carbon dioxide

Conduction: Transfer of heat through solid medium
Convection: Transfer of heat through fluids (liquids and gases)
Radiation: Transfer of heat through vacuum

Surface tension is the force or property of a liquid which makes the surface to behave as if it were a stretched elastic skin or membrane.

Protons are positively charged. Hence since there are 4 protons, the atom has 4 positively charged particles.

Only plants manufacture their own food.