Write true or false: Gases are highly compressible as compared to solids and liquids. Colloids are homogeneous mixtures. Valency is the combining capacity of an atom. Cell is a latin word meaning ‘a little room’. Aluminium is diatomic. By applying force on the wall, work done is zero.

Answer: $\boxed{\text{26.85 }^\circ\text{C}}$

b) 293 K

Answer: $\boxed{\text{19.85 }^\circ\text{C}}$

OR

Convert the following temperatures into Kelvin scale.

To convert Celsius to Kelvin, use the formula: $\text{K} = ^\circ\text{C} + 273.15$

a) 25$^\circ$C

Answer: $\boxed{\text{298.15 K}}$

b) 373$^\circ$C

Answer: $\boxed{\text{646.15 K}}$

Q.6 Write any two properties of suspension.

Properties of suspension:

• A suspension is a heterogeneous mixture in which solid particles are dispersed in a liquid or gas.
• The particles in a suspension are large enough to be seen with the naked eye and will settle down over time if left undisturbed.
• The particles in a suspension scatter a beam of light passing through it (Tyndall effect).

OR

Differentiate between homogeneous and heterogeneous mixture.

Homogeneous Mixture:

• Has a uniform composition throughout.
• Components are indistinguishable from each other.
• Examples: Saltwater, air.

Heterogeneous Mixture:

• Has a non-uniform composition.
• Components are visible and distinguishable from each other.
• Examples: Sand and water, oil and water.

Q.7 Calculate the molecular mass of NaHCO$_3$.

Atomic masses:
Na = 23 u
H = 1 u
C = 12 u
O = 16 u

Na: 1 atom
H: 1 atom
C: 1 atom
O: 3 atoms

Mass of Na = $1 \times 23 \text{ u} = 23 \text{ u}$
Mass of H = $1 \times 1 \text{ u} = 1 \text{ u}$
Mass of C = $1 \times 12 \text{ u} = 12 \text{ u}$
Mass of O = $3 \times 16 \text{ u} = 48 \text{ u}$

Molecular mass of NaHCO$_3$ = $23 + 1 + 12 + 48 = 84 \text{ u}$
Answer: $\boxed{\text{84 u}}$

OR

Define ion with the help of example.

An ion is an atom or molecule that has gained or lost one or more electrons, resulting in it carrying a net electrical charge (either positive or negative).
Example: A sodium atom (Na) loses one electron to become a positively charged sodium ion (Na$^+$). A chlorine atom (Cl) gains one electron to become a negatively charged chloride ion (Cl$^-$).

Q.8 Write Thomson's atomic model.

Thomson's atomic model (also known as the "plum pudding model") states:

• An atom consists of a positively charged sphere.
• The electrons are embedded within this sphere, like plums in a pudding.
• The positive and negative charges are equal in magnitude, making the atom electrically neutral overall.

OR

If an atom contains one electron and one proton, will it carry any charge or not?

Answer: No, it will not carry any net charge.
A proton has a charge of +1 unit, and an electron has a charge of -1 unit. If an atom has one proton and one electron, their charges cancel each other out ($+1 + (-1) = 0$), resulting in a net charge of zero.

Q.9 Difference between plant cell and animal cell.

Plant Cell:

• Has a rigid cell wall outside the cell membrane.
• Contains chloroplasts for photosynthesis.
• Usually has a large, central vacuole.
• Typically has a fixed, rectangular shape.

Animal Cell:

• Lacks a cell wall.
• Does not contain chloroplasts.
• Has small, temporary vacuoles or no vacuoles.
• Typically has an irregular or rounded shape.

OR

Where do the lipids and proteins constituting the cell membrane get synthesized?

Synthesis of lipids and proteins for the cell membrane:

• Proteins are primarily synthesized on ribosomes (some free, some attached to the endoplasmic reticulum) and then processed and modified in the endoplasmic reticulum (ER) and Golgi apparatus.
• Lipids (like phospholipids) are mainly synthesized in the smooth endoplasmic reticulum (SER).

Q.10 Write Archimedes principle and its applications.

Archimedes' Principle:
It states that when an object is wholly or partially immersed in a fluid, it experiences an upward buoyant force that is equal to the weight of the fluid displaced by the object.

Applications:

• Designing ships and submarines: It explains why ships float and how submarines control their buoyancy.
• Hydrometers: Used to measure the density of liquids.
• Hot air balloons: The principle applies to gases as well, explaining how balloons float.

OR

What do you mean by buoyant force?

Buoyant force is the upward force exerted by a fluid (liquid or gas) that opposes the weight of an immersed object. This force is caused by the pressure difference between the top and bottom surfaces of the object submerged in the fluid.

Q.11 If a person covers two rounds of circular ground of r radius. Write the distance and displacement covered by him.

Given:
Radius of circular ground = $r$
Number of rounds = 2

The distance covered in one round is equal to the circumference of the circle.
Circumference = $2\pi r$

Total distance = Number of rounds $\times$ Circumference
Total distance = $2 \times (2\pi r) = 4\pi r$
Answer (Distance): $\boxed{4\pi r}$

Displacement is the shortest distance between the initial and final positions. After completing two full rounds of a circular path, the person returns to their starting point.
Initial position = Final position
Answer (Displacement): $\boxed{0}$