Density is the relation between the mass of a material and the volume it takes up.
The density of a substance is its mass per unit of its volume. It’s the measurement of how tightly the matter is packed together.
The Density of Water can be defined as the weight of the water per unit volume. Density of water is dependent on the temperature of the water. The density of water is 1 gram/ cubic centimetre (1 g/cm3) approximately.
Question 1: What is the density of water in kilograms per cubic metre?
Answer: Option b) 1000 kg/m3
Explanation: We know the approximate density of water is 1 g/cm3
1 g = 0.001 kg
1 cm = 0.01 m
1 g/cm3 = (0.001 kg/0.01 m) 3 = 1000 kg/m3
Therefore, density of water converted to kg/m3 is 1000 kg/m3
Question 2: At what temperature pure water has maximum density?
Answer: Option b)
Explanation: Around temperature, pure water has maximum density. The hydrogen bond formation in water is maximum at this temperature resulting in increased density.
Question 3: What is the effect of an increase in temperature on density of water?
a) It increases.
b) It decreases fromtothen increases.
c) It decreases.
d) It increases fromtothen decreases.
Answer: Option d) It increases from to then decreases.
Explanation: On increasing temperature, the density of water follows an unusual pattern as compared to other liquids. It increases from to decreases. The density is maximum at
Question 4: Which of the following has the least density?
Answer: Option a) Oil
Explanation: Oil is least dense among the given options, followed by water and milk. Honey has maximum density.
Question 5: Why does ice float in water?
a) Ice is less dense than water.
b) The density of water and ice is the same.
c) Ice is denser than water.
d) Because ice is solid.
Answer: Option a) Ice is less dense than water.
Explanation: Water has maximum density at 4°C. Water freezes at 0°C and becomes ice. The density of ice is less than liquid water, therefore ice floats on water.
Question 6: On freezing the volume of water-
c) Stay the same.
d) All of the above.
Answer: option a) Increases.
Explanation: The volume of water increases on freezing, because in liquid water there is compact hydrogen bonding that exists among water molecules. In ice, the hydrogen bonds are forced apart and that results in an increase of volume.
Question 7: Wood floats in water. If measured , water and wood will have greater mass for the same volume.
a) The water would have a greater mass.
b) The water would have a lower mass.
c) Both water and wood will have the same mass.
d) The mass of the wood and water would both be 100 grams.
Answer: Option a) The water would have a greater mass.
Explanation: Wood floats on water, because it is less dense than water. We know density is the mass per unit volume of a substance.
As density is directly proportional to mass, For the same volume, mass of water would be greater than wood.
Question 8: A tiny sand grain is very light but sinks in water, because?
a) Sand is solid.
b) Sand is less dense than water.
c) There is more water than sand.
d) Sand is denser than water.
Answer: Option d) Sand is denser than water.
Explanation: A tiny sand grain sand will sink because sand is denser than water. If we could weigh a small amount of water having the same volume as the grain of sand, the sand grain will weigh more than the water. Therefore, the grain of sand sinks.
Question 9: Why is the density of hot and cold water different?
a) In hot water, molecules move slower and are slightly closer together.
b) The size of molecules is larger in hot water.
c) The molecules in hot water move faster and are slightly further apart.
d) In cold water, the molecules move faster and are further apart.
Answer: Option c) The molecules in hot water move faster and are slightly further apart
Explanation: In hot water, molecules move faster and are slightly further apart when we cool water, the molecules start to slow down and get slightly closer together, this results in molecules occupying a smaller volume and therefore, in an increase in density.
Question 10: Why does a carrot float in salt water but sinks in freshwater?
a) Salt water is more dense than freshwater.
b) Fresh water is more dense than salt water.
c) The carrot is denser as compared to saltwater.
d) Fresh Water is denser than a carrot.
Answer: Option a) Salt water is more dense than freshwater
Explanation: When an object has higher density than the liquid it sinks and when an object has lower density than the liquid it floats.
Carrot is more dense than fresh water and hence sinks in it. But, when salt is dissolved in the water, the density of the water increases and the salt water becomes more dense than the carrot, making the carrot float in the salt water.
Density of a substance is defined as its mass per unit volume. Density () is represented by -
= density, m= mass, v= volume.
Water has density of one gram per cubic centimetre(1g/cm3)
When water is heated, its density changes. On heating, water expands and increases in volume. The warmer the water, the more space it takes, and the lower its density. On freezing, water turns into ice and the density of ice is also lower than liquid water.
The density of pure water is approximately one gram per one milliliter.
However, this density of water changes when temperature is increased or decreased.
The density of water is not constant, it changes with increase or decrease in temperature. On heating, water expands and increases in volume. The warmer the water, the more space it takes, and the lower its density. On freezing, water turns into ice and the density of ice is also lower than liquid water.