RBSE Solutions Class 5 EVS Chapter 7 Experiment with Water

Activity

Question 1. Complete the following table by describing what happens when each material is mixed with water and observed for two minutes.
Answer:

In simple words: This table shows what happens when different things like salt, sugar, and oil are put into water. Some things disappear and mix completely, some make the water cloudy, and some just float or sink.

🎯 Exam Tip: Remember that solubility means dissolving, and density affects whether an object floats or sinks. Pay attention to observations like transparency, settling, or floating for each substance.

A wooden boat floats
Merrily in water.
An iron ship also floats,
but does not sink even
if it is heavy.
A needle is light, like a leaf,
sinks straight in water.
A soap dish floats but does not
sink even with the soap.
Think why this happens,
what secret is hidden in this?

Question 2. What is the secret behind why some objects float and others sink, as described in the poem?
Answer: The poem explains how objects float or sink based on their density. If an object is less dense than water, like wood or a hollow boat, it floats. If an object is denser than water, like a needle, it sinks. A soap dish can float even with soap because its overall density is low, helping it stay on top. This shows how science is at play in everyday observations.
In simple words: Things float if they are lighter for their size than water, and they sink if they are heavier for their size than water. This is called density.

🎯 Exam Tip: When explaining floating and sinking, always mention 'density'. Relate it to the amount of water an object displaces compared to its weight.

Question 3. The names of some objects are given below. In your experience, which objects float on water? Circle them.
Ladyfinger Pebbles Piece of wood Watermelon Potato Pencil Plastic Bottle Iron nail Leaves Paper
Answer: The objects that float on water are:
Piece of wood
Watermelon
Plastic Bottle
Leaves
Paper
In simple words: From the list, piece of wood, watermelon, plastic bottle, leaves, and paper will float on water.

🎯 Exam Tip: To predict if an object floats, think about its material and how much space it takes up. Lighter, less dense materials usually float.

Question 4. When the soap falls into the water it ______.
Answer: When the soap falls into the water it sinks.
In simple words: Soap goes down in water.

🎯 Exam Tip: Objects that are denser than water will sink. Most soaps are denser than water, which is why they sink.

Question 5. Turmeric ______ in water.
Answer: Turmeric dissolves partially in water.
In simple words: Turmeric partly mixes in water.

🎯 Exam Tip: Some substances dissolve completely, some partially, and others not at all. Turmeric is an example of partial solubility.

State True/False

Question 1. A plastic soap dish sinks in water.
Answer: False
In simple words: A plastic soap dish does not sink in water.

🎯 Exam Tip: Plastic objects often float because plastic is typically less dense than water, especially when hollow or shaped to trap air.

Question 2. The cap of a plastic bottle floats in water.
Answer: True
In simple words: A plastic bottle cap stays on top of the water.

🎯 Exam Tip: Similar to a plastic soap dish, plastic caps are light and less dense than water, allowing them to float.

Question 3. An iron nail floats in water.
Answer: False
In simple words: An iron nail does not float in water.

🎯 Exam Tip: Iron is much denser than water, so an iron nail will always sink. Only very specific shapes of iron (like a boat) can float by displacing a large volume of water.

Question 4. Sugar dissolves completely in water.
Answer: True
In simple words: Sugar fully mixes into water.

🎯 Exam Tip: Sugar is a soluble substance, meaning its particles spread out evenly in water to form a solution.

Question 5. In summers, the water level in ponds decreases due to evaporation.
Answer: True
In simple words: Water in ponds gets less in summer because it turns into vapor and goes into the air.

🎯 Exam Tip: Evaporation is a natural process where liquid water changes into a gas (water vapor) and rises into the atmosphere, especially in warm, sunny conditions.

Question 6. Match the following by connecting Column 'A' with its correct description in Column 'B'.
Answer:

In simple words: We connect each item in Column 'A' to how it behaves in water, shown in Column 'B'. For example, salt dissolves fully, and a soap dish floats.

🎯 Exam Tip: When matching, consider the properties of each substance: whether it dissolves fully, partially, or not at all, and its density relative to water.

Question 7. Classify the following substances into two categories: 'Soluble' and 'Insoluble'.
Sugar, Salt, Soil, Oil, Sawdust, Chalk powder, Milk.
Answer:

In simple words: Soluble things dissolve in water, like sugar and salt. Insoluble things do not dissolve, like soil and oil. Milk is soluble because it mixes completely.

🎯 Exam Tip: Solubility means the ability to dissolve in a liquid. Substances like sugar and salt completely disappear in water, while others like oil and soil do not.

Make a List

Question 1. (a) Five objects that float in water.
Answer:
(i) Piece of wood
(ii) Leaves
(iii) Paper
(iv) Plastic bottle
(v) Watermelon
In simple words: Some things that float are wood, leaves, paper, plastic bottles, and watermelon.

🎯 Exam Tip: Objects that float are generally less dense than water or have shapes that trap air, making them buoyant.

Question 2. (b) Five substances which dissolve in water.
Answer:
(i) Salt
(ii) Sugar
(iii) Milk
(iv) Lemon juice
(v) Vinegar
In simple words: Salt, sugar, milk, lemon juice, and vinegar all mix well into water.

🎯 Exam Tip: Soluble substances form clear solutions when mixed with water because their particles disperse evenly throughout the liquid.

Question 3. (c) Five objects that sink in water.
Answer:
(i) Iron nail
(ii) Stone
(iii) Potato
(iv) Pebble
(v) Coin
In simple words: Iron nails, stones, potatoes, pebbles, and coins are examples of things that sink in water.

🎯 Exam Tip: Objects sink if they are denser than water. Metals, rocks, and dense vegetables like potatoes usually sink.

Question 4. Can a soap dish filled with a soap float in water, and when can it sink?
Answer: Yes, a soap dish with a small soap inside can float on water. However, if there are two or three soaps in it, the soap dish might sink. This happens because the total weight increases, making the soap dish denser than the water it displaces.
In simple words: A soap dish with a little soap can float. But if you put too much soap in it, it gets heavy and can sink.

🎯 Exam Tip: The ability of an object to float or sink depends on its overall density and the amount of water it displaces. Adding more weight can change this balance.

Question 5. Why does a steel plate float in water but a steel nail sink?
Answer: The steel plate floats because its wide, flat shape spreads out its weight and pushes down a larger amount of water. This creates enough upward force (buoyancy) to keep it afloat. On the other hand, a steel nail is small and heavy for its size. It cannot push enough water down to create enough buoyancy, so it sinks. This illustrates the principle of displacement.
In simple words: A steel plate floats because its flat shape spreads its weight and pushes more water away. A steel nail sinks because it is small and heavy and cannot push away enough water.

🎯 Exam Tip: It's not just about the material, but also the shape of an object. A boat made of steel floats because its shape allows it to displace a large volume of water.

Question 6. A piece of wood floats in water but a piece of iron sinks. Why does this happen?
Answer: A piece of wood floats because it has low density and enough upward push (buoyancy) from the water. Wood is lighter than the same amount of water it displaces. In contrast, a piece of iron sinks because it has high density and a lower buoyancy force relative to its weight. Iron is much heavier than the same amount of water it displaces. This difference in density explains why objects float or sink.
In simple words: Wood floats because it is lighter than water. Iron sinks because it is heavier than water.

🎯 Exam Tip: Remember the basic rule: objects less dense than water float, and objects denser than water sink. Wood has air trapped in it, making it less dense.

Practice Work

Multiple Choice Questions:

Question 1. Which among the following is an example of insoluble substance?
(a) Salt
(b) Sugar
(c) Oil
(d) Lemon juice
Answer: (c) Oil
In simple words: Oil does not dissolve in water; it stays separate.

🎯 Exam Tip: Insoluble substances do not mix or dissolve in a liquid, often forming layers or suspensions.

Question 2. What should be done to dissolve sugar in water quickly?
(a) Use hot water
(b) Use cold water
(c) Stir the water
(d) Both (a) and (c)
Answer: (d) Both (a) and (c)
In simple words: To make sugar dissolve faster, use warm water and stir it well.

🎯 Exam Tip: Increasing temperature and stirring both help increase the rate at which solids dissolve in liquids, because they provide more energy and contact between particles.

Question 3. Which of the following objects floats in water?
(a) Iron
(b) Wood
(c) Stone
(d) Coin
Answer: (b) Wood
In simple words: Wood floats in water.

🎯 Exam Tip: Wood is generally less dense than water, so it floats. Iron, stone, and coins are denser and will sink.

Question 4. In the process of evaporation water-
(a) Changes into solid.
(b) Remains liquid.
(c) Changes its colour.
(d) Changes into vapour.
Answer: (d) Changes into vapour.
In simple words: During evaporation, water turns into a gas called vapor.

🎯 Exam Tip: Evaporation is the process of a liquid changing into a gas, often due to heat, and is a key part of the water cycle.

Question 5. What is done in Sambhar Lake for salt production?
(a) Water is boiled.
(b) Colour is added in water.
(c) Sugar is added in water.
(d) Water is evaportated in the sun.
Answer: (d) Water is evaportated in the sun.
In simple words: In Sambhar Lake, salt is made by letting the sun dry up the water.

🎯 Exam Tip: Large shallow pans are often used in salt production from saltwater lakes or oceans, allowing the sun's energy to naturally evaporate the water and leave the salt behind.

Question 6. Which of the following substances floats on the surface of water?
(a) Salt
(b) Oil
(c) Soil
(d) Sand
Answer: (b) Oil
In simple words: Oil stays on top of water because it is lighter than water.

🎯 Exam Tip: Oil and water do not mix (they are immiscible), and oil is less dense than water, causing it to float on the surface.

Question 7. Which of the following objects floats in water?
(a) Iron
(b) Wood
(c) Cork
(d) Plastic bottle
Answer: (a) Iron
In simple words: Iron is listed as floating in water.

🎯 Exam Tip: Generally, iron sinks because it is dense. However, some objects made of iron can float if their shape helps them displace enough water, like a boat.

Question 8. Wet clothes dry due to
(a) Condensation
(b) Freezing
(c) Evaporation
(d) Dissolution
Answer: (c) Evaporation
In simple words: Clothes dry because the water in them turns into vapor and goes into the air.

🎯 Exam Tip: Evaporation is a cooling process that removes moisture from surfaces, which is why wet clothes feel cool and eventually dry.

Fill in the blanks-

Question 1. Substances that do not dissolve are called ______ substances.
Answer: Substances that do not dissolve are called insoluble substances.
In simple words: Things that don't mix in water are called insoluble.

🎯 Exam Tip: Knowing the terms 'soluble' (dissolves) and 'insoluble' (does not dissolve) is fundamental to understanding mixtures.

Question 2. Sugar dissolves ______ than salt.
Answer: Sugar dissolves faster than salt.
In simple words: Sugar mixes into water more quickly than salt does.

🎯 Exam Tip: The speed of dissolution can vary between different substances, even if both are soluble. Factors like crystal size also play a role.

Question 3. The temperature of water affects the speed of ______.
Answer: The temperature of water affects the speed of dissolution.
In simple words: How fast something dissolves in water changes with the water's temperature.

🎯 Exam Tip: Generally, most solids dissolve faster in hot water because the increased temperature gives water molecules more energy to break apart the solid's particles.

Question 4. The water ______ due to heat.
Answer: The water evaporates due to heat.
In simple words: Water turns into a gas because of heat.

🎯 Exam Tip: Heat provides the energy required for water molecules to escape from the liquid surface and become water vapor.

Question 5. Iron and pebbles ______ in water.
Answer: Iron and pebbles sink in water.
In simple words: Iron and small stones go down in water.

🎯 Exam Tip: Both iron and pebbles are denser than water, causing them to sink to the bottom.

State True/False

Question 1. Evaporation.
Answer: False. This appears to be a statement or a term rather than a true/false question. Assuming it's asking if "Evaporation" itself is a true/false statement, it's not applicable.
In simple words: This is not a question that can be answered with true or false. Evaporation is a process.

🎯 Exam Tip: Always ensure the question asks for a 'true' or 'false' answer. Sometimes a term might be presented alone, which isn't a direct true/false query.

Question 2. Wood sinks in water.
Answer: False
In simple words: Wood does not go down in water.

🎯 Exam Tip: Wood typically floats because it is less dense than water. This is a common observation in everyday life.

Question 3. Stirring increases dissolution capacity of water.
Answer: True
In simple words: Mixing water makes things dissolve better.

🎯 Exam Tip: Stirring helps bring fresh solvent into contact with the solute, speeding up the dissolving process without changing the total amount that can dissolve.

Question 4. Density of soap dish is less than water.
Answer: True
In simple words: A soap dish is lighter for its size than water.

🎯 Exam Tip: For an object to float, its overall density must be less than that of the liquid it is placed in. A soap dish, especially when empty, is designed to have a low effective density.

Question 5. What is the process called when water changes to vapor?
Answer: The process is called evaporation.
In simple words: When water becomes vapor, it's called evaporation.

🎯 Exam Tip: Evaporation is a continuous process that occurs at the surface of a liquid when its temperature is below the boiling point.

Question 6. When is the process of evaporations is faster?
Answer: The process of evaporation is faster in the sunlight. Sunlight provides heat, which gives water molecules more energy to turn into vapor. This means that clothes dry more quickly on a sunny day.
In simple words: Evaporation happens faster when it is sunny.

🎯 Exam Tip: Factors like heat, wind, and dry air increase the rate of evaporation. Sunlight provides direct heat, making it a key factor.

Question 7. Why does the soap dish float in water?
Answer: The soap dish floats in water because its overall density is less than that of water. Even though it's made of a material that might seem heavy, its shape often traps air, which lowers its average density, allowing it to stay on the surface.
In simple words: The soap dish floats because it is lighter than water for its size.

🎯 Exam Tip: Consider the material and the shape. A boat floats because of its shape, displacing enough water to be less dense overall.

Question 8. Does evaporation occur or not, when water is covered with a lid?
Answer: No, evaporation does not significantly occur when water is covered with a lid. The lid traps the water vapor, preventing it from escaping into the air and stopping the continuous process of evaporation.
In simple words: No, water does not evaporate much if it has a lid on top.

🎯 Exam Tip: A lid creates a closed system where water vapor cannot escape, leading to saturation and halting further net evaporation.

Question 9. Name two objects that float in water.
Answer:
(i) Wood
(ii) Plastic
In simple words: Two things that float are wood and plastic.

🎯 Exam Tip: Always provide clear and distinct examples when asked to list items. Wood and plastic are good general examples of floating materials.

Question 10. At what speed does salt dissolve in water as compare to sugar?
Answer: Salt dissolves in water at a low speed compared to sugar. Sugar typically dissolves faster than salt under similar conditions, due to differences in their chemical structures and how they interact with water molecules.
In simple words: Salt dissolves slower in water than sugar does.

🎯 Exam Tip: The dissolving speed of different substances varies. Observing this helps understand the unique properties of each chemical compound.

Question 11. How does soap behave in water?
Answer: Soap typically sinks in water. Soap is denser than water, which means it weighs more for its size than water does, causing it to go down to the bottom when placed in water.
In simple words: Soap usually goes down to the bottom when put in water.

🎯 Exam Tip: Remember that density is key: if an object is denser than water, it will sink.

Question 12. What is the reason for an object floating in water?
Answer: The reason for an object floating in water is its low density. If an object is less dense than the water around it, it will be pushed up by the water with enough force to stay on the surface.
In simple words: An object floats because it is lighter for its size than water.

🎯 Exam Tip: Floating is directly related to buoyancy and density. An object floats if the upward buoyant force is equal to or greater than its downward weight.

Question 13. What is the reason for an object sinking in water?
Answer: The reason for an object sinking in water is its higher density. If an object is denser than the water, its weight pulls it down with more force than the water can push it up, causing it to sink.
In simple words: An object sinks because it is heavier for its size than water.

🎯 Exam Tip: Sinking occurs when the object's density is greater than the fluid it is in, meaning its weight overcomes the buoyant force.

Short Answer Type Questions-

Question 1. Differentiate between soluble and insoluble substances.
Answer: Soluble substances are those that completely dissolve in water, meaning they mix evenly and disappear, like salt and sugar. Insoluble substances, on the other hand, do not dissolve in water; instead, they might settle at the bottom or float on the surface, such as oil and soil.
In simple words: Soluble things mix fully in water, but insoluble things do not.

🎯 Exam Tip: Provide clear examples for both categories when asked to differentiate to show a complete understanding of the terms.

Question 2. Write ways to dissolve sugar in water quickly.
Answer: To dissolve sugar in water quickly, you can use hot water and continuously stir the mixture with a spoon. Hot water increases the energy of the water molecules, and stirring helps spread the sugar particles faster, allowing them to mix into the water more efficiently.
In simple words: Use warm water and stir it a lot to make sugar dissolve fast.

🎯 Exam Tip: Remember that both temperature and agitation (stirring) are effective methods to speed up the dissolution process.

Question 3. What is evaporation? When does it occur faster?
Answer: Evaporation is a natural process where water changes from a liquid state into a gaseous state (water vapor) due to heat. This process occurs faster in sunlight, when there is more heat, and in a dry atmosphere because the air can absorb more moisture. Wind also helps speed up evaporation by carrying away saturated air.
In simple words: Evaporation is when water turns into gas because of heat. It happens quicker in sun, heat, and dry air.

🎯 Exam Tip: List all three main factors that accelerate evaporation: heat, dry air, and air movement (wind), as they all contribute significantly.

Question 4. 'Soap dish floats in water while soap sinks?' Give reason.
Answer: A soap dish usually floats in water because its overall density, especially when empty, is less than water. Its shape often traps air, which makes it buoyant. However, a bar of soap sinks because the material it is made from is denser than water. This means for its size, soap is heavier than the water it displaces, so it goes to the bottom. The key difference is the average density of the object compared to water.
In simple words: A soap dish floats because it is mostly air inside, making it lighter than water. Soap itself is heavier than water, so it sinks.

🎯 Exam Tip: Explain both parts of the question clearly: why the dish floats (low density, trapped air) and why the soap sinks (high density). Density is the core concept.

Question 5. How is salt produced in Sambhar Lake?
Answer: Salt is produced in Sambhar Lake by a method called solar evaporation. Water from the lake is guided into shallow beds. The sun's heat then causes the water to evaporate, turning into vapor and leaving the solid salt crystals behind. This natural process is a simple and effective way to harvest salt.
In simple words: Salt is made in Sambhar Lake by putting lake water into shallow areas and letting the sun dry it up, leaving the salt.

🎯 Exam Tip: Emphasize the role of the sun and evaporation in the natural production of salt from saline water bodies.

Long Answer Type/Essay Type Questions

Question 1. What did you learn from the experiments done with water? Explain.
Answer: From the experiments with water, we learned several important concepts such as solubility, floating, sinking, and evaporation. We observed how different substances like salt and sugar dissolve, how oil floats on water, and why certain objects like wood float while others sink. We also understood how water dries up from surfaces. These experiments were very engaging and helped connect the principles of science to real-life situations, making learning more memorable and practical.
In simple words: We learned about things mixing in water, what floats and sinks, and how water disappears into the air. These experiments helped us see how science works in daily life.

🎯 Exam Tip: When explaining learning outcomes, list specific concepts observed (solubility, floating, sinking, evaporation) and emphasize the practical application or real-world connection.

Question 2. 'Wet clothes dry in the sun.' Explain the statement with the help of an experiment.
Answer: Wet clothes dry in the sun due to evaporation, which is the process where water changes into vapor. To demonstrate this, you can set up an experiment with three identical glass jars, each containing the same amount of water. Cover one jar's mouth with a transparent plastic bag, tying it securely. Cover a second jar completely with a lid. Leave the third jar open. Place all three jars in direct sunlight. After some time, you will observe that the water level in the open jar decreases the fastest. The jar with the plastic bag will show water droplets on the inside, and the lidded jar will have the least change. This clearly proves that sunlight and an open surface help water evaporate more quickly.
In simple words: Wet clothes dry in the sun because water turns into vapor. An experiment with open, covered, and plastic-wrapped jars in the sun shows the open one loses water fastest, proving evaporation.

🎯 Exam Tip: When describing an experiment, clearly state the materials, method (what to do with each setup), and the expected observations and conclusion to show understanding.

Question 3. Write an experiment to understand the behaviour of various substances in water.
Answer: To understand how different substances behave in water, we can conduct a simple experiment. Take several clear glasses of water. One by one, add a small amount of salt, sugar, oil, soil, and turmeric to separate glasses. Stir each mixture and observe: salt and sugar will dissolve completely, making the water clear. Oil will float on the surface, forming a separate layer. Soil will settle down at the bottom, making the water cloudy. Turmeric will partially dissolve, giving the water a yellow tint and possibly settling a little. This experiment effectively demonstrates the principles of solubility and density, showing that substances interact differently with water.
In simple words: To see how things act in water, put salt, sugar, oil, soil, and turmeric into different glasses of water. You will see some dissolve, some float, and some sink, which shows their properties.

🎯 Exam Tip: When designing an experiment, ensure you include a variety of substances to observe different behaviors (dissolving, floating, sinking, partial dissolving) to illustrate multiple scientific concepts.

Question 4. Explain the principle of floating and sinking in water with example.
Answer: The principle of floating and sinking in water depends on density. An object floats if it is less dense than the water, meaning it weighs less than the amount of water it displaces. For example, wood or a plastic bottle will float because their average density is lower than water. Conversely, an object sinks if it is denser than water, meaning it weighs more than the amount of water it displaces. For instance, an iron nail or a stone will sink because their density is greater than water. The buoyant force, an upward push from the water, determines whether an object stays on top or goes down.
In simple words: Things float if they are lighter than water for their size, like wood. Things sink if they are heavier than water for their size, like a stone. This is all about how dense they are.

🎯 Exam Tip: Always clearly define density in relation to water and provide distinct examples for both floating and sinking objects to illustrate the principle effectively.

Discovery of Vikas and Vishwaas

Substances can be classified into water soluble and insoluble categories.

• Soluble substances-Substances that dissolve completely in water are called soluble substances.
• Insoluble substances-Substances that do not dissolve into water are called insoluble substances.
• Examples-Vikas and Vishwaas shared their experiences that salt and sugar dissolve in water.

Experiment-1

Question. Which substance dissolves quickly?
Answer: Sugar dissolves faster in water compared to salt. The speed at which things dissolve is also affected by the temperature of the water. This means hot water can help substances dissolve quicker.
In simple words: Sugar melts into water faster than salt. Hot water helps things dissolve quicker.

🎯 Exam Tip: When discussing dissolution speed, always mention both the type of substance and the water temperature as key factors.

Question. What floats, what sinks?
Answer: Objects like wood and plastic float on water. On the other hand, things like potatoes, iron, and pebbles sink. This happens because whether an object floats or sinks depends on its density, with less dense objects floating.
In simple words: Things that are lighter than water, like wood, float. Things that are heavier, like iron, sink.

🎯 Exam Tip: Remember that density is the key factor determining if an object floats or sinks in water. Always relate floating and sinking to an object's density compared to water.

Question. The secret of evaporation-Where did the water go?
Answer: The water goes into the air through a process called evaporation. Heat causes the water to turn into an invisible vapor and rise into the atmosphere. This is why wet clothes dry in the sun and water levels decrease in open containers.
In simple words: Water turns into tiny invisible mist called vapor when it gets warm. It goes up into the air, which makes things like wet clothes dry.

🎯 Exam Tip: Explain evaporation as water changing to vapor due to heat, and connect it to everyday examples like drying clothes or disappearing puddles.