The Amazing World of Solutes, Solvents & Solutions Class 8 (Curiosity)

Q 1
Question
State whether the statements given below are True [T] or False [F]. Correct the false statement(s).
(i) Oxygen gas is more soluble in hot water rather than in cold water.
(ii) A mixture of sand and water is a solution.
(iii) The amount of space occupied by any object is called its mass.
(iv) An unsaturated solution has more solute dissolved than a saturated solution.
(v) The presence of different gases in the atmosphere is also a uniform mixture.
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Q 2
Question
Fill in the blanks.
(i) The volume of a solid can be measured by displacement, where the solid is ____ in water and the ____ in water level is measured.
(ii) The maximum amount of ____ dissolved in ____ at a particular temperature is called solubility.
(iii) Generally, the density ____ with increase in temperature.
(iv) A solution in which glucose has fully dissolved and no more can dissolve is called a ____ solution of glucose.
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Q 3
Question
You pour oil into a glass containing some water. The oil floats on top. What does this tell you?
(i) Oil is denser than water
(ii) Water is denser than oil
(iii) Oil and water have the same density
(iv) Oil dissolves in water
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Q 4
Question
A stone sculpture weighs 225 g and has a volume of 90 cm³. Calculate its density and predict whether it will float or sink in water.
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Q 5
Question
Which one of the following is the most appropriate statement, and why are the other statements not appropriate?
(i) A saturated solution can still dissolve more solute at a given temperature.
(ii) An unsaturated solution has dissolved the maximum amount of solute possible at a given temperature.
(iii) No more solute can be dissolved into the saturated solution at that temperature.
(iv) A saturated solution forms only at high temperatures.
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Q 6
Question
You have a bottle with a volume of 2 litres. You pour 500 mL of water into it. How much more water can the bottle hold?
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Q 7
Question
An object has a mass of 400 g and a volume of 40 cm³. What is its density?
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Q 8
Question
Analyse Fig. 9.25a and 9.25b. Why does the unpeeled orange float, while the peeled one sinks? Explain.
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Q 9
Question
Object A has a mass of 200 g and a volume of 40 cm³. Object B has a mass of 240 g and a volume of 60 cm³. Which object is denser?
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Q 10
Question
Reema has a piece of modeling clay that weighs 120 g. She first moulds it into a compact cube of volume 60 cm³. Later, she flattens it into a thin sheet. Predict what will happen to its density.
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Q 11
Question
A block of iron has a mass of 600 g and a density of 7.9 g/cm³. What is its volume?
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Q 12
Question
You are provided with an experimental setup as shown in Fig. 9.26a and 9.26b. On keeping the test tube (Fig. 9.26b) in a beaker containing hot water (~70°C), the water level in the glass tube rises. How does it affect the density?
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Project 1
Project
Research project on Dead Sea: Why is there no aquatic life in the Dead Sea? Try to find out if there are any other similar water bodies.
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Key Points
Extreme salt makes the Dead Sea unfit for most life.
Key Points / Good Practices
The Dead Sea has a very high salt concentration.
So much salt makes the water very dense and harsh.
Most fish and plants cannot survive in it.
The high density is why people float easily there.
Look up other salty lakes, such as the Great Salt Lake.
Note your sources and present your findings neatly.
The Dead Sea's extreme saltiness stops aquatic life; compare it with other salt lakes.

Project 2
Project
Investigate how well common salt dissolves in different solvents, such as water, vinegar, and oil. Compare the solubility of salt in each solvent and record your observations.
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Key Points
Salt dissolves well in water, less in vinegar, not in oil.
Key Points / Good Practices
Use the same amount of salt and solvent for a fair test.
Stir each for the same time and observe.
Salt dissolves easily in water.
It dissolves in vinegar too, as vinegar is mostly water.
Salt does not dissolve in oil.
Record your observations in a neat table.
A fair test shows salt dissolves in water and vinegar but not in oil.

Project 3
Project
Debate in class—Is water truly the most versatile solvent?
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Key Points
Water dissolves many things, but not everything.
Key Points / Good Practices
For: water dissolves salt, sugar, and many substances.
For: it is often called the universal solvent.
For: it is safe, cheap, and used in medicine and cooking.
Against: water cannot dissolve oil or wax.
Against: some substances need other solvents like alcohol.
Conclude with a balanced view backed by examples.
Water dissolves a huge range of substances but not all, so the debate has two fair sides.