Physical quantities and measurements

Question 1

What is density?

Answer 1

Density is defined as mass per unit volume of the substance.

Question 2

What is the formula of density?

Answer 2

Density= mass/volume

Question 3

What are the SI and CGS unit of density

Answer 3

The SI unit of density is kg/m³ and the CGS unit is g/cm³

Question 4

Density unit related formula?

Answer 4

1kg/1m³= 1000g/100cm×100cm×100cm=1g/1000cm

Question 5

List the density of these following common substances:

1. Lead
2. Glycerine
3. Wood (oak)
4. Iron
5. Steel
6. Mercury
7. Petrol

Answer 5

1. 11340
2. 1260
3. 700-900
4. 7800
5. 7900
6. 13600
7. 700

Question 6

How can we find the density of an irregular solid by using a measuring cylinder?

Answer 6

First, find the mass of the given irregular solid. Now to find the volume, fill the measuring cylinder partially with water. Note the initial volume of water as V¹. The the irregular solid to a piece of thread and completely immerse it in water. When the water level rises, mark the new water kevel as V². Find the difference between the final and the initial levels of water. This gives the volume of the given solid. Once the volume and mass is found, find the density of the solid using the formula D=M/V.

Question 7

How to find the density of liquids without using the density bottle?

Answer 7

Find the mass of the empty measuring cylinder using a beam balance (m¹). Pour a certain volume of liquid in. Find the mass of the cylinder again with the liquid (m²). Then find the actual mass by subtracting the first mass m¹ from the second mass m². Find the volume of the liquid using a measuring cylinder and then find the density using the formula: d=m/v

Question 8

How to measure the density of a liquid using a density bottle?

Answer 8

Find the mass of an empty density bottle (m¹). Fill it completely with water and insert the stopper. Find its mass again (m²). Empty the bottle again and fill it completely with the liquid and insert the stopper. Find the mass again (m³). Note that the volume of the liquid and water are same. Since density of water= 1g/cm³ and mass of water=volume of water
The volume of water=(m²-m¹) cm³
Volume of given liquid= “ “ “
Density can now be calculated using the formula m/v=m³-m¹/m²_m¹

Question 9

Define relative density.

Answer 9

The ratio of density of the substance to the density of water at 4°C. Its also known as specific gravity. It also has no unit.

Question 10

Formula of relative density?

Answer 10

Rd= density of substance/density of water at 4°C

OR

Rd= (mass of substance)÷volume/(mass of water)÷volume

Question 11

Explain the anomalous expansion of water.

Answer 11

It contracts when heated from 0°C to 4°C and hence, its density increases. When heated above 4°C, the water expands and its density decreases.

Question 12

Define convection currents and give natural examples.

Answer 12

Circular movements or currents within a fluid (liquid or gas) due to different densities of hotter and cooler parts.
Example: blowing of wind,land breeze, boiling of water, etc.