i) Plastics do not decompose or biodegrade.
ii) One-time use plastics are responsible for littering the environment and clogging drains.
iii) Standing water breeds mosquitoes which cause malaria, dengue and chikungunya.
iv) Animals confuse plastic for food and eat it by accident.
v) Plastics cannot be digested and stays in intestine leads to harmful diseases.
vi) Microbeads present in household products washed down in drains and end up in soil pollution and water pollution

(i) Spiral galaxy
(ii) Elliptical galaxy
(iii) Barred spiral galaxy
(iv) Irregular galaxy

The levels of classification are 
1. kingdom
2. phylum
3. classes
4. order
5. families
6. genus and
7. species

Smooth ER and Rough ER

Cell wall and Cell membrane

Chloroplast and Mitochondria

\(\begin{array}{|c|l|l|} \hline \text { S.No. } &{\text { Physical change }} &{\text { Chemical change }} \\ \hline \text { 1. } & \text { No new substance are formed } & \text { New substance are formed } \\ \hline 2 . & \text { Chemical properties do not change } & \text { Chemical properties changed } \\ \hline 3 . & \text { It is a temporary action. } & \text { It is a permanent action. } \\ \hline 4 . & \text { It is a reversible reaction } & \text { It is a irreversible reaction. } \\ \hline \end{array}\)

The flow of electric charges constitute an electric current. An electric current is measured by the amount of electric charge moving per unit time at any point in the circuit

a) Its expansion is uniform (for equal amounts of heat it expands by equal length)
b) It is opaque and shining
c) It is a good conductor of heat.
d) It does not stick to the sides of the glass tube.
e) So mercury is used in the thermometer
f) Water cannot used in thermometer.
1) Its expansion is not in uniform.
2) It is stick to the sides of the glass tube.

(i) Atoms of the different elements can have the same number of neutrons are called "Isotones".
(ii) Ex : ₂₉Ca⁴⁰ and ₁₉K³⁹
(iii) Numbers of neutrons = A - Z = 20

i) We have to brush two times a day,it will prevent the formation of tartar and plaque on your teeth and gums.
ii) We have to floss it will remove food particles, plaque and bacteria which buildup between your teeth

A molecule is made up of two or more atoms chemically combined.

Pollen grains are transferred from the anther of one flower to the stigma of another flower of the same kind or different plant is known as cross pollination.

Density of a substance is defined as the mass of the substance contained in unit volume (1 m³).
Density (D) = mass (M)/volume(V)
D = M/V
SI unit of density - kg/m³