The Amazing World of Solutes, Solvents, and Solutions Class 8 Extra Questions and Answers Science Chapter 9

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Class 8 Science Chapter 9 The Amazing World of Solutes, Solvents, and Solutions Extra Questions

Class 8 Science Chapter 9 Extra Questions on The Amazing World of Solutes, Solvents, and Solutions

The Amazing World of Solutes, Solvents, and Solutions Class 8 Very Short Question Answer

Question 1.
What do you use to treat oral dehydration at home?
Answer:
ORS (Oral Rehydration Solution)

Question 2.
Predict whether a mixture of sugar and water is uniform or non-uniform.
Answer:
Uniform

Question 3.
Name some non-uniform mixtures.
Answer:
Mixture of chalk and water.

Question 4.
What is one solute in a solution of two liquids?
Answer:
The one present in a smaller amount.

Question 5.
What other name is given to a uniform mixture?
Answer:
Solution

Question 6.
Name three possible solutes present in the air.
Answer:
Oxygen, carbon dioxide, argon, etc.

Question 7.
What do you call a solution in which more salt can be dissolved?
Answer:
Unsaturated Solution

Question 8.
What is termed as concentration?
Answer:
The amount of solute in a fixed quantity of solution is termed its concentration.

Question 9.
How does the solubility of solids change with the temperature rise?
Answer:
The solubility will increase with the rise in temperature.

Question 10.
What maintains aquatic life in water?
Answer:
A small amount of oxygen is dissolved in water.

Question 11.
Out of husk particles or iron sticks, which will float on water?
Answer:
Husk Particles.

Question 12.
How is the density of a substance measured?
Answer:
The ratio of mass to volume of a substance gives its density.

Question 13.
What appliance do you use to measure the mass of a substance?
Answer:
Digital Weighing Balance

Question 14.
Define Volume.
Answer:
Volume is the space occupied by an object.

Question 15.
How does the density of a substance change with temperature?
Answer:
Generally, the density of a substance decreases with the rise of temperature.

Question 16.
What is the mass of 1 mL of water?
Answer:
1 gm

The Amazing World of Solutes, Solvents, and Solutions Class 8 Short Question Answer

Question 1.
Why do sugar and salt dissolve in water but not in oil?
Answer:
Water can disperse particles of salt or sugar. But oil cannot do so.

Question 2.
Why are water bottles usually tall and cylindrical in shape instead of spherical?
Answer:
Tall and cylindrical bottles can indicate very small changes in volume.

Question 3.
How will you change an unsaturated solution to a saturated solution?
Answer:
We will add more and more salt to the unsaturated solution till it dissolves.
When the solute stops dissolving and starts settling at the bottom, it becomes a saturated solution.

Question 4.
In a mixture of sawdust or sand in water, which mixture is called a solution? In which case, the so-added substance will float or sink?
Answer:
Both mixtures are non-uniform and are not called solutions. The sawdust will float on water as it is lighter than water. Sand will sink as it is heavier than water.

Question 5.
Which is heavier: a wooden stick or an iron rod? Explain.
Answer:
An iron rod is heavier than a wooden stick.
A wooden stick can displace more liquid and thus its density is lower than that of an iron rod.

Question 6.
Give the SI unit of density.
Answer:
kg/m3 or 1000 g/1000 L or g/L or g/1000 mL

Question 7.
Differentiate between mass and weight.
Answer:
Mass is the quantity of matter present in an object or a substance. Its units are gram (g) or kilogram (kg).
On the other hand, weight is the force by which the Earth attracts an object towards itself. Its unit is newton (N).

Question 8.
Give the formula to calculate the volume of a regular object.
Answer:
Volume = length × width × height = cm³

The Amazing World of Solutes, Solvents, and Solutions Class 8 Long Question Answer

Question 1.
Comment on dilute solution and concentrated solution. Which of them gives the solubility of the solute? Explain.
Answer:
Dilute and concentrated solutions are relative terms. The solution obtained by dissolving one teaspoonful of salt in 100 mL of water is dilute compared to a solution obtained by dissolving two spoonfuls of salt in 100 mL of water. None of these gives the solubility of the salt. The idea of solubility can be obtained by dissolving the maximum amount of salt in a fixed quantity of a solvent at a given temperature. Solubility changes with temperature. In the case of a solid solution, solubility increases, but in the case of a gaseous solution, the solubility decreases.

Question 2.
Explain the term density, giving its units and dependence on temperature and pressure.
Answer:
Density is defined as the mass present in a unit volume of a substance.
Density = \(\frac {Mass}{Volume}\)
The units in which density is expressed will depend upon the units of mass and volume.
If the units of mass and volume are kilogram (kg) and cubic metre (m³) respectively.
The SI unit of density is kilogram per cubic metre (kg/m³).
For liquid units of density is used in grams per milliliter (g/mL).

The density of a substance is independent of its shape and size but depends on temperature and pressure. The effect of pressure on the density of solids and liquids is negligible, but the density of gases decreases. If we compare the density of two substances, it is called relative density. It is a number without units. For example, the mass of an aluminium block is 27 g and its volume is 10 cm³, so its density is 2.7 g/cm³. But its relative density with respect to water is 2.7, i.e., it is 2.7 times heavier than water.

Question 3.
What is mass? How is it measured?
Answer:
Mass is the quantity of matter present in any object. It can be measured as follows using a digital weighing balance:

• Switch on the digital balance.
• Observe the initial reading on the digital balance display.
• See that it is zero. If not, use the button to bring it to zero.
• Now, place a clean and dry watch glass on the pan.
• Note the reading on the digital balance; let it be A.
• Now, carefully place the solid object, such as a stone, on the watch glass.
• Note the reading displayed on the balance; let it be B.
• Mass of the stone = (B – A) g.
• The mass of a liquid may be measured by replacing the watch glass with a beaker and putting the liquid into it.

Question 4.
Define volume. How is it measured?
Answer:
Volume is the space occupied by an object. The common apparatus used to measure the volume of liquids is a measuring cylinder. It is a narrow, transparent, cylindrical container with one side open and the other side closed. These are mostly made of a transparent body. Measuring cylinders are available in different sizes to measure volumes: 5 mL, 10mb, 25 mL, 50 mL, 100 mL, 250 mL, etc. We can measure up to an accuracy of 0.1 mL. Now proceed as follows:

• Place a clean, dry measuring cylinder on a flat surface.
• Pour liquid slowly into the measuring cylinder.
• The liquid in the cylinder forms a curved surface.
• Read the marks on the measuring cylinder with the bottom of the meniscus for water and other colourless liquids, and the upper meniscus in case of coloured liquids.
• The reading on the cylinder gives the volume of the liquid in mL.
• You can choose a cylinder of any size depending on the amount of liquid to be measured.

Volume of Solids
A. Volume of regular shape solids can be calculated by the following formula:
Volume = 1 × w × h = cm³
B. Volume of irregular solids can be measured by the following steps:

• Fill a measuring cylinder up to half its capacity. Record the initial reading. Let it be V₁.
• Tie the object, say a stone, with a thread and lower it in the measuring cylinder.
• Record the final reading. Let it be V₂.
• Volume of object = (V₂ – V₁) cm³

Question 5.
What are solutions? How are these helpful in medicinal formulations?
Answer:
Solutions refer to the presence of dissolved substances in solvents, mostly water. We can have a dilute solution or a concentrated solution. These are comparative terms. A dilute solution can be a small amount of dissolved substance, and a concentrated solution contains a higher amount of dissolved substances. We can also have an unsaturated solution and a saturated solution. A saturated solution has the maximum amount of solute dissolved at a fixed temperature. But an unsaturated solution can have more solute dissolved at a given temperature.

A saturated solution becomes unsaturated at higher temperatures. Conversely, an unsaturated solution becomes saturated at a lower temperature. For medicinal formulations, only dilute solutions are used. Generally, drug formulations are prepared using water as a solvent. The Indian system of medicine also refers to the use of oil, ghee, milk, and other substances as solvents for drug formulations to achieve the beneficial strength of the drug. In some cases, some solvents are used to extract and isolate important compounds from plants. Asima Chatterjee was given the Shanti Swarup Bhatnagar Award for her work on the isolation of important medicinal compounds from plants.

The Amazing World of Solutes, Solvents, and Solutions Class 8 Case Based Questions

Question 1.
Riya is preparing lemonade for her friends on a hot summer day. She takes a jug of water, adds some sugar, and stirs it well. Then, she squeezes some lemons into the jug and mixes everything. She notices that the sugar completely disappears, but the lemon pulp settles down a bit after some time.
(a) In Riya’s lemonade, identify the solute(s) and the solvent.
(b) Why did the sugar dissolve completely in the water, but the lemon pulp settled down?
(c) If Riya wants the sugar to dissolve faster, what could she do?
Answer:
(a) The solutes are sugar and lemon juice. The solvent is water.
(b) Sugar is soluble in water, forming a homogeneous mixture (a solution). The sugar particles are very small and become evenly distributed throughout the water. Lemon pulp, however, is mostly insoluble in water, meaning it doesn’t dissolve completely and will eventually settle down, forming a heterogeneous mixture.
(c) She would raise via temperature of the sample by keeping in hot water bath.

Question 2.
A group of students is experimenting. They have two beakers, A and B, each containing 100 mL of water. In beaker A, they add 5 grams of salt and stir. In beaker B, they add 20 grams of salt and stir. They observe that all the salt in beaker A dissolves, but in beaker B, some salt remains at the bottom, even after stirring vigorously.
(a) Why did all the salt dissolve in beaker A, but not in beaker B?
(b) What kind of solution is formed in beaker A?
(c) What about beaker B (considering the undissolved salt)?
Answer:
(a) In beaker A salt added was lower in amount than its solubility, but the salt in beaker B had reached its solubility limit unsaturated solution.
(b) In beaker A unsaturated solution is formed.
(c) In beaker B saturated solution is formed.

The Amazing World of Solutes, Solvents, and Solutions Extra Questions for Practice

Question 1.
Define a solution.

Question 2.
What is a solute?

Question 3.
What is a solvent?

Question 4.
Why is water called the universal solvent?

Question 5.
Give one example of a solution.

Question 6.
Explain the difference between a solute and a solvent with an example.

Question 7.
How does temperature affect the solubility of most solids in liquids?

Question 8.
Why do gases dissolve better in liquids at lower temperatures?

Question 9.
Differentiate between a dilute and a concentrated solution.

Question 10.
What is an aqueous solution? Give an example.

Question 11.
Describe what a solution is and explain its key characteristics. Discuss how solutions differ from suspensions and colloids in terms of particle size, appearance, and stability.

Question 12.
Explain the concept of solubility and the various factors that affect it.

Question 13.
Imagine you are preparing a saturated sugar solution at room temperature. Describe the steps you would take and explain what would happen if you then: (a) heated the solution, and (b) added more sugar and stirred without changing the temperature.