NCERT Science Ch 2: Is Matter Around Us Pure?
NCERT Science Ch 2: Is Matter Around Us Pure?
Start an exciting journey through NCERT Science Chapter 2: "Is Matter Around Us Pure?" This guide will cover pure substances, mixtures, elements, compounds, and how to separate them. You'll learn about the purity of matter in our world.
Key Takeaways
- Discover the scientific classification of matter as pure substances and mixtures.
- Understand the fundamental building blocks of matter: elements and compounds.
- Explore the different types of mixtures and the techniques used to separate them.
- Gain insights into the practical applications of pure substances and mixtures in everyday life.
- Recognize the importance of material purity and its environmental impact.
Exploring the Purity of Matter Around Us
In our daily lives, we see many materials. From the air we breathe to the things around us. But, are these substances pure, or are they made of different parts? We'll look into the world of matter and see how pure our environment is.
Matter can be simple or complex. Pure substances have only one type of particle. Mixtures are made of more than one substance. Knowing the difference helps us understand the world better.
Now, let's check the purity of things around us. Look at your surroundings. You might see a glass of water, a wooden table, or a plastic pen. These items might be pure substances or mixtures. By studying their properties, we can figure out what they are.
| Pure Substances | Mixtures |
|---|---|
| Consist of a single type of particle (element or compound) | Contain two or more pure substances |
| Have a constant composition | Can have variable composition |
| Have a fixed set of physical properties | Can have a range of physical properties |
| Cannot be separated into simpler substances by physical means | Can be separated into their constituent pure substances by physical means |
As we explore matter's purity, we'll see how substances and mixtures work together. This understanding will reveal the complexity of our world.
"The essence of the universe is purity, and the essence of purity is simplicity."
Understanding Matter: A Scientific Perspective
In science, knowing about matter is key. Matter is everything around us, from air to solid objects. It's the basic stuff of our world. Let's explore what matter is and its different forms.
What is Matter?
Matter is anything with mass and takes up space. It's the stuff of our world, coming in many forms. Matter is made of atoms and molecules, the smallest parts of everything.
States of Matter
The states of matter are the ways matter can be. The main ones are solid, liquid, and gas. Each has its own properties of matter, like shape and volume. These depend on how atoms or molecules are arranged.
- Solid: Solids keep their shape and volume. Their atoms or molecules are close together and organized.
- Liquid: Liquids take the shape of their container but keep their volume. Their atoms or molecules are less packed, allowing them to flow.
- Gas: Gases don't have a fixed shape or volume. They expand to fill their container. Their atoms or molecules are far apart and move freely.
These states can change, like when something melts or boils. This happens when temperature or pressure changes.
Knowing about the states of matter and their properties of matter helps us understand our world. It's important for understanding everything from water to air.
Pure Substances and Mixtures
Matter in our world falls into two main groups: pure substances and mixtures. Knowing the difference between them is key to understanding the properties of different materials.
Identifying Pure Substances
A pure substance has the same physical and chemical properties everywhere. These include melting and boiling points, and density. These properties help us identify the substance. Pure substances can be elements or compounds and stay the same no matter where they come from.
To spot a pure substance, we look at its physical and chemical traits. Some signs include:
- Consistent and reproducible physical properties
- Definite chemical composition
- Ability to be separated into its original state through physical methods
- Lack of variation in properties, even from different sources
Mixtures, on the other hand, are made of two or more substances that aren't chemically joined. They can be either homogeneous or heterogeneous, based on how uniform they are and if you can see their parts.
"The ability to identify pure substances is fundamental to understanding the composition and behavior of matter around us."
Learning to identify pure substances helps us grasp the world of materials. This knowledge is vital in fields like chemistry, physics, engineering, and our daily lives.
Elements: The Building Blocks of Matter
Elements are the basic building blocks of our world. They make up everything, from the air we breathe to the ground we walk on. These elements are the simplest pure substances.
The periodic table helps us understand these elements. It organizes them by their atomic structure. This makes it easier to see their properties and how they relate to each other.
The periodic table shows us everything from hydrogen to oganesson. Each element has its own unique traits. These traits, like color and state of matter, affect the pure substances they create.
| Element | Atomic Number | Symbol | State of Matter |
|---|---|---|---|
| Hydrogen | 1 | H | Gas |
| Helium | 2 | He | Gas |
| Lithium | 3 | Li | Solid |
| Beryllium | 4 | Be | Solid |
Learning about elements helps us understand pure substances. This knowledge is key to exploring our world.
"The periodic table is like a temple... a magnificent, ordered structure that helps illuminate the mystery of the world around us."
- Theodore Gray, author of "The Elements"
Compounds: Unique Combinations of Elements
Compounds are key in chemistry. They are made when elements bond together. This creates a new substance with special properties.
By studying compounds, we learn about matter's complex nature. We see how it works.
Chemical Formulas and Naming
Chemical formulas show what a compound is made of. They use symbols and subscripts to show the number of atoms. Knowing how to read these formulas is important.
Naming compounds has its own rules. These rules help us talk about chemicals clearly. They apply to simple and complex substances alike.
"The language of chemistry is the language of chemical formulas and equations." - Theodore W. Richards
Learning about compounds, chemical formulas, and naming conventions is essential. These basics help us understand the material world better. They are the foundation for exploring the chemical universe.
Mixtures: A Blend of Substances
The world is full of mixtures, where different substances blend together. These blends can be different in many ways. Knowing about these mixtures helps us understand the world better.
Types of Mixtures
Mixtures are mainly divided into two types: homogeneous and heterogeneous. Let's look at each type:
- Homogeneous Mixtures: These mixtures have all parts evenly mixed. They look and act the same everywhere. Examples include saline solution, alloys, and air.
- Heterogeneous Mixtures: These mixtures have parts that are not evenly mixed. You can see different parts, like oil and water in salad dressing. Examples include sand and water, fruit salad, and mixed nuts.
| Characteristic | Homogeneous Mixtures | Heterogeneous Mixtures |
|---|---|---|
| Appearance | Uniform, single phase | Non-uniform, multiple phases |
| Composition | Evenly distributed components | Unevenly distributed components |
| Examples | Saline solution, air, alloys | Salad dressing, sand and water, fruit salad |
Knowing about types of mixtures helps us understand the world better. Each type has its own special properties and uses.
https://youtube.com/watch?v=Ot_nOrkFgsw
Separating Mixtures: Techniques and Methods
In the world of chemistry, knowing how to separate mixtures is key. It's important for students, scientists, and anyone curious about the world. Let's look at how to separate mixtures using different techniques.
Physical Separation Methods
Physical methods use differences in size, density, or boiling point to separate. These are used in labs and industries. Here are some common techniques:
- Filtration: It separates solids from liquids by using a filter.
- Distillation: It separates liquids based on their boiling points.
- Chromatography: It separates substances based on how they interact with different materials.
- Centrifugation: It separates substances by spinning them at high speeds.
Chemical Separation Methods
Chemical methods use the unique properties of each substance. They are more complex but very effective. Here are some examples:
- Crystallization: It separates solids from solutions by forming crystals.
- Precipitation: It separates solids from solutions by adding a chemical that causes them to form.
- Extraction: It separates substances by dissolving them in a specific solvent.
- Chromatography: It separates substances based on their interactions with different materials, like in physical methods.
Learning about separation techniques helps us understand the world better. Whether you're studying a solution, purifying a compound, or exploring nature, these methods are crucial. They are essential for anyone who wants to learn more about the world.
Identifying Pure Substances and Mixtures
Knowing if something is pure or a mixture is key to understanding materials. We can tell by looking at physical properties. This helps us learn about the makeup and purity of things we see every day.
The melting point is a big clue for identifying pure substances. They melt at a sharp, clear point, showing they're made of the same stuff. Mixtures, on the other hand, melt at different temperatures because they're made of different things.
The boiling point also tells us about purity. Pure substances boil at a specific temperature. But mixtures boil at different temperatures because each part boils at its own rate.
Other signs include color, density, and solubility. By looking at these, we can tell if something is pure or mixed. This helps us understand what we see around us better.
Using these physical properties, we can discover the secrets of the world around us. We learn the differences between pure substances and mixtures. This knowledge helps us make better choices in life, from picking products to taking care of the environment.
Complete Content Science NCERT Chapter 2 Is Matter Around Us Pure
In the captivating NCERT Science Chapter 2, "Is Matter Around Us Pure?", we explore the basics of matter. This chapter covers how matter is classified, the differences between pure substances and mixtures, and how to separate them.
The chapter starts by explaining what matter is. It talks about its three main states: solid, liquid, and gas. It then explains the difference between pure substances and mixtures, helping students understand these concepts.
This chapter focuses on elements, the basic building blocks of matter. Students learn about elements' unique properties and how they form compounds. It also explores the world of mixtures, looking at their types and how to separate them.
| Key Concepts Covered | Subtopics Explored |
|---|---|
| Classification of Matter |
|
| Separation Techniques |
|
The ncert science chapter 2 also talks about the practical uses of pure substances and mixtures. It shows how they are important in our daily lives. From understanding the air we breathe to seeing how industries separate materials, this chapter is full of real-world examples.
"Understanding the nature of matter is the foundation for exploring the world around us."
By the end of this chapter, students will deeply understand the ncert science chapter 2. They will see how it connects to the scientific study of the complete content science ncert chapter 2 is matter around us pure.
Applications of Pure Substances and Mixtures
In our daily lives, we see many pure substances and mixtures. They are everywhere, from the water we drink to the materials in our homes. These substances are key to our everyday experiences.
Everyday Examples
Water is a prime example of a pure substance. It's vital for staying hydrated and cleaning. It's also used in many industrial processes and household products like shampoos and detergents.
Alloys, made from mixing metals, are used in many ways. Stainless steel, for example, is strong and resistant to corrosion. It's found in kitchen appliances, construction, and medical tools.
Household items like baking soda, vinegar, and salt are mixtures with practical uses. Baking soda helps in baking, while vinegar is great for cleaning and adding flavor. Salt, a mix of sodium and chloride, is key for seasoning and keeping our bodies balanced.
| Pure Substance | Application |
|---|---|
| Water | Hydration, cleaning, industrial processes |
| Stainless Steel | Kitchen appliances, construction materials, medical equipment |
| Baking Soda | Leavening agent in baking |
| Vinegar | Cleaning agent, flavoring |
| Salt | Seasoning, electrolyte balance |
These examples show how pure substances and mixtures are part of our daily lives. They highlight their importance and usefulness.
Environmental Impact of Impurities
In our modern world, the purity of matter is key to our environment. Impurities in the air, water, or soil can harm us and nature. It's vital to understand how these impurities affect us and our planet.
Pollution is a big worry. Pollutants like industrial waste and microplastics can dirty our air, water, and land. This makes our environment worse and risks our health and nature's balance.
Water purification is also crucial. Clean drinking water is essential for our health and the planet's. But, impurities like heavy metals and bacteria in water can harm us and nature.
Thanks to science, we have new ways to fight these problems. New technologies help clean our air, water, and manage waste. These steps lead us to a cleaner, more sustainable world.
"The health of our environment is directly linked to the purity of the matter that surrounds us. By understanding and addressing the impact of impurities, we can take crucial steps towards safeguarding our planet for generations to come."
We must keep watching over our environment and its purity. By using green practices, supporting new tech, and caring for nature, we can make our planet healthier. This way, we can lessen the harm of impurities and protect our planet.
Scientific Advancements in Material Purity
The world of materials science has seen big changes lately. New technologies and scientific breakthroughs are leading the way. Nanotechnology and biotechnology are changing how we make and purify materials.
Nanotechnology: Redefining Purity at the Atomic Scale
Nanotechnology lets us control materials at a tiny scale. Scientists can now make very pure and special materials. This technology has opened up new areas in material purity, like better filters and self-cleaning surfaces.
Biotechnology: Nature-Inspired Purification Techniques
Biotechnology uses nature to solve problems. It's helping make materials purer and more sustainable. This includes new ways to clean water and make medicines.
The future of material purity looks bright. With nanotechnology and biotechnology, we'll see even more progress. These technologies will help us create new, advanced materials.
"The ability to manipulate individual atoms and molecules is a great opportunity to make a tremendous difference in the way we live our lives."
- Richard Feynman, Nobel Laureate in Physics
Hands-on Activities and Experiments
Learning about pure substances and mixtures can be fun with hands-on activities and experiments. These experiences make you understand better and spark curiosity about the world.
Try the Separation of Mixtures experiment. Mix salt, sand, and iron filings. Then, use methods like filtration and magnetic separation to separate them. This shows how to tell pure substances from mixtures.
The Chromatography of Ink is another cool activity. Use different-colored pens and chromatography paper to see how ink dyes separate. It shows that mixtures can have many different substances.
For a fun density experiment, get coins, beads, and marbles. Watch how they act in liquids of different densities. This teaches you about density and how it affects substances.
"The best way to learn is to do. The only way to learn a new programming language is by writing programs." - John Kemeny
These activities are just a start to exploring pure substances and mixtures. By doing experiments, you'll learn more and love science even more.
Revisiting Key Concepts and Takeaways
As we wrap up our journey through NCERT Science Chapter 2, "Is Matter Around Us Pure?", let's revisit the main concepts and takeaways. We've looked into the complex world of matter. We've learned about the differences between pure substances and mixtures, how to separate them, and why purity matters in our lives and science.
We've discovered that matter can be in solid, liquid, or gas states, each with its own traits. We've identified pure substances and understood how elements combine to form compounds. We've also learned various ways to separate mixtures, helping us understand the world around us better.
Reviewing this chapter, we gain the power to tell if substances are pure. We see how impurities affect our environment and the advancements in material science. This knowledge will help us as we dive deeper into chemistry and its impact on our lives.
FAQ
What is the difference between a pure substance and a mixture?
A pure substance has only one type of molecule or atom. A mixture, on the other hand, is made of two or more substances that aren't chemically joined.
How can you identify a pure substance?
You can spot a pure substance by its constant physical properties. These include melting point, boiling point, and density, which don't change with sample size.
What are the different types of mixtures?
Mixtures are divided into two types: homogeneous and heterogeneous. Homogeneous mixtures have the same composition everywhere. Heterogeneous mixtures have different parts that don't mix well.
What are the common methods for separating mixtures?
To separate mixtures, you can use methods like filtration, distillation, evaporation, and chromatography. Chemical methods include precipitation, crystallization, and fractional distillation.
What is the role of elements in the composition of pure substances?
Elements are the basic units of matter. Pure substances are made of one element or a fixed mix of elements.
How are chemical formulas and compound names related?
Chemical formulas show what a compound is made of. Naming conventions give each compound a unique name based on its formula and structure.
What is the environmental impact of impurities in substances?
Impurities, like pollutants, can harm the environment. They can pollute water and air, disrupt ecosystems, and affect human health. Keeping substances pure is key for a healthy planet.
How are scientific advancements shaping the understanding and applications of material purity?
New technologies, like nanotechnology and biotechnology, are changing how we view material purity. They help create better, more efficient, and eco-friendly materials.
Question 1:
What is meant by a pure substance?
Solution:
A pure substance is the one that consists of a single type of particles, i.e., all constituent particles of the substance have the same chemical nature. Pure substances can be classified as elements or compounds.
Question 2:
List the points of differences between homogeneous and heterogeneous mixtures.
Solution:
A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example: salt in water, sugar in water, copper sulphate in water. A heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example: sodium chloride and iron fillings, salt and sulphur, oil and water.
Question 3:
Differentiate between homogeneous and heterogeneous mixtures with examples.
Solution:
A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example, mixtures of salt in water, sugar in water, copper sulphate in water, iodine in alcohol, alloy, and air have uniform compositions throughout the mixtures. On the other hand, a heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example, compositions of mixtures of sodium chloride and iron fillings, salt and sulphur, oil and water, chalk powder in water, wheat flour in water, milk and water are not uniform throughout the mixtures.
Question 4:
How are sol, solution, and suspension different from each other?
Solution:
Sol is a heterogeneous mixture. In this mixture, the solute particles are so small that they cannot be seen with the naked eye. Also, they seem to be spread uniformly throughout the mixture. The Tyndall effect is observed in this mixture. For example: milk of magnesia, mud. Solution is a homogeneous mixture. In this mixture, the solute particles dissolve and spread uniformly throughout the mixture. The Tyndall effect is not observed in this mixture. For example: salt in water, sugar in water, iodine in alcohol, alloy. Suspensions are heterogeneous mixtures. In this mixture, the solute particles are visible to the naked eye and remain suspended throughout the bulk of the medium. The Tyndall effect is observed in this mixture. For example: chalk powder and water, wheat flour and water.
Question 5:
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
Solution:
Mass of solute (sodium chloride) = 36 g (Given)
Mass of solvent (water) = 100 g (Given)
Then, mass of solution = Mass of solute + Mass of solvent = (36 + 100) g = 136 g
Therefore, concentration (mass by mass percentage) of the solution = (Mass of solute / Mass of solution) * 100% = (36 / 136) * 100% ≈ 26.47%
Note: According to the law of conservation of mass, the mass of the solute and solvent before and after dissolving remains the same.
Question 6:
How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?
Solution:
A mixture of two miscible liquids having a difference in their boiling points more than 25°C can be separated by the method of distillation. Thus, kerosene and petrol can be separated by distillation. In this method, the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it. We also need a beaker, a water condenser, and a Bunsen burner. The apparatus is arranged as shown in the above figure. Then, the mixture is heated slowly. The thermometer should be watched simultaneously. Petrol will vaporize and condense in the water condenser. The condensed petrol is collected from the condenser outlet, whereas kerosene is left behind in the distillation flask.
Question 7:
Name the technique to separate:
- (i) butter from curd → Centrifugation
- (ii) salt from sea-water → Evaporation
- (iii) camphor from salt → Sublimation
Question 8:
What type of mixtures are separated by the technique of crystallisation?
Solution:
By the technique of crystallisation, pure solids are separated from impurities. For example, salt obtained from the sea is separated from impurities; crystals of alum (Phitkari) are separated from impure samples.
Question 9:
Classify the following as chemical or physical changes:
- Cutting of trees → Physical change
- Melting of butter in a pan → Physical change
- Rusting of almirah → Chemical change
- Boiling of water to form steam → Physical change
- Passing of electric current through water, and water breaking down into hydrogen and oxygen gas → Chemical change
- Dissolving common salt in water → Physical change
- Making a fruit salad with raw fruits → Physical change
- Burning of paper and wood → Chemical change
Question 10:
Try segregating the things around you as pure substances or mixtures.
Solution:
Pure substance: Water, salt, sugar
Mixture: Saltwater, soil, wood, air, cold drink, rubber, sponge, fog, milk, butter, clothes, food
Question 11:
Which separation techniques will you apply for the separation of the following?
- (a) Sodium chloride from its solution in water. → Evaporation
- (b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. → Sublimation
- (c) Small pieces of metal in the engine oil of a car. → Centrifugation or filtration or decantation
- (d) Different pigments from an extract of flower petals. → Chromatography
- (e) Butter from curd. → Centrifugation
- (f) Oil from water. → Using separating funnel
- (g) Tea leaves from tea. → Filtration
- (h) Iron pins from sand. → Magnetic separation
- (i) Wheat grains from husk. → Winnowing
- (j) Fine mud particles suspended in water. → Centrifugation
Question 12:
Write the steps you would use for making tea. Use the words: solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Solution:
First, water is taken as a solvent in a saucer pan. This water (solvent) is allowed to boil. During heating, milk and tea leaves are added to the solvent as solutes. They form a solution. Then, the solution is poured through a strainer. The insoluble part of the solution remains on the strainer as residue. Sugar is added to the filtrate, which dissolves in the filtrate. The resulting solution is the required tea.
Question 13:
Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).
| Temperature in K | Potassium nitrate | Sodium chloride | Potassium chloride |
|---|---|---|---|
| 283 | 21 | 35 | 37 |
| 293 | 32 | 36 | 46 |
| 313 | 36 | 35 | 55 |
| 333 | 35 | 37 | 37 |
| 353 | 37 | 62 | 54 |
(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?
(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
(c) Find the solubility of each salt at 293 K. What salt has the highest solubility at this temperature?
(d) What is the effect of the change of temperature on the solubility of a salt?
Solution:
(a) At 313 K, 62 grams of Potassium nitrate dissolved in 100 grams of water. So to produce a saturated solution of potassium nitrate in 50 grams of water, we need
\( \frac{62 \times 50}{100} \) grams of potassium nitrate
(b) Some soluble potassium chloride will separate out in the form of crystals at room temperature because the solubility of potassium chloride will decrease with a decrease in temperature.
(c) Solubility of each salt at 293 K:
| 293 K | |
|---|---|
| Potassium nitrate | 32 grams |
| Sodium chloride | 36 grams |
| Potassium chloride | 35 grams |
| Ammonium chloride | 37 grams |
What salt has the highest solubility at this temperature? The solubility of Ammonium chloride is highest at this temperature.
(d) The solubility of salt increases with an increase in temperature.
Question 13:
Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).
| Temperature (K) | Potassium nitrate | Sodium chloride | Potassium chloride | Ammonium chloride |
|---|---|---|---|---|
| 283 | 21 | 24 | 37 | 106 |
| 293 | 32 | 36 | 46 | 167 |
| 313 | 36 | 35 | 55 | 37 |
| 333 | 35 | 37 | 37 | 54 |
| 353 | 35 | 62 | 54 | 66 |
- (a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?
- (b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
- (c) Find the solubility of each salt at 293 K. What salt has the highest solubility at this temperature?
- (d) What is the effect of change of temperature on the solubility of a salt?
Solution:
- (a) At 313 K, 62 grams of Potassium nitrate dissolved in 100 grams of water. So to produce a saturated solution of potassium nitrate in 50 grams of water, we need
\( \frac{62 \times 50}{100} = 31 \) grams of potassium nitrate - (b) Some soluble potassium chloride will separate out in the form of crystals at room temperature because the solubility of potassium chloride will decrease with decrease in temperature.
-
- Solubility of Potassium nitrate at 293 K is 32 grams.
- Solubility of Sodium chloride at 293 K is 36 grams.
- Solubility of Potassium chloride at 293 K is 46 grams.
- Solubility of Ammonium chloride at 293 K is 167 grams.
- The solubility of salt increases with increase in temperature.
Question 14:
Explain the following giving examples:
- (a) Saturated solution
- (b) Pure substance
- (c) Colloid
- (d) Suspension
Solution:
-
(a) Saturated solution:
A saturated solution is a solution in which the maximum amount of solute has been dissolved at a given temperature. The solution cannot dissolve beyond that amount of solute at that temperature. Any more solute added will settle down at the bottom of the container as a precipitate.
Example: If 500 g of a solvent can dissolve a maximum of 150 g of a particular solute at 40°C, then the solution obtained by dissolving 150 g of that solute in 500 g of that solvent at 300 K is said to be a saturated solution at 300 K. -
(b) Pure substance:
A pure substance is a substance consisting of a single type of particles, i.e., all constituent particles of the substance have the same chemical properties.
Example: Salt, sugar, water are pure substances. -
(c) Colloid:
A colloid is a heterogeneous mixture. The size of the solutes in this mixture is so small that they cannot be seen individually with naked eyes and seem to be distributed uniformly throughout the mixture. The solute particles do not settle down when the mixture is left undisturbed. This means that colloids are quite stable. Colloids cannot be separated by the process of filtration. They can be separated by centrifugation. Colloids show the Tyndall effect.
Example: Milk, butter, foam, fog, smoke, clouds. -
(d) Suspension:
Suspensions are heterogeneous mixtures. The solute particles in this mixture remain suspended throughout the bulk of the medium. The particles can be seen with naked eyes. Suspension shows the Tyndall effect. The solute particles settle down when the mixture is left undisturbed. This means that suspensions are unstable. Suspensions can be separated by the method of filtration.
Example: Mixtures of chalk powder and water, wheat flour and water.
Question 15:
Classify each of the following as a homogeneous or heterogeneous mixture.
Soda water, wood, air, soil, vinegar, filtered tea
Solution:
Homogeneous mixtures: Soda water, air, vinegar
Heterogeneous mixtures: Wood, soil, filtered tea
Question 16:
How would you confirm that a colorless liquid given to you is pure water?
Solution:
Every liquid has a characteristic boiling point. Pure water has a boiling point of 100°C (373 K) at 1 atmospheric pressure. If the given colorless liquid boils at even slightly above or below 100°C, then the given liquid is not pure water. It must boil at sharp 100°C. Thus, by observing the boiling point, we can confirm whether a given colorless liquid is pure water or not.
Question 17:
Which of the following materials fall in the category of a “pure substance”?
- Ice
- Milk
- Iron
- Hydrochloric Acid
- Calcium oxide
- Mercury
- Brick
- Wood
- Air
Solution:
The following materials fall in the category of a “pure substance”:
- Ice
- Iron
- Hydrochloric acid
- Calcium oxide
- Mercury
Question 18:
Identify the solutions among the following mixtures:
- Soil
- Sea water
- Air
- Coal
- Soda water
Solution:
The following mixtures are solutions:
- Sea water
- Air
- Soda water
Question 19:
Which of the following will show the “Tyndall effect”?
- Salt solution
- Milk
- Copper sulphate solution
- Starch solution
Solution:
Milk and starch solution will show the “Tyndall effect”.
Question 20:
Classify the following into elements, compounds, and mixtures:
| Substance | Classification |
|---|---|
| Sodium | Element |
| Soil | Mixture |
| Sugar solution | Mixture |
| Silver | Element |
| Calcium carbonate | Compound |
| Tin | Element |
| Silicon | Element |
| Coal | Mixture |
| Air | Mixture |
| Soap | Mixture |
| Methane | Compound |
| Carbon dioxide | Compound |
| Blood | Mixture |
Question 21:
Which of the following are chemical changes?
- Growth of a plant
- Rusting of iron
- Mixing of iron fillings and sand
- Cooking of food
- Digestion of food
- Freezing of water
- Burning of candle
Solution:
The following changes are chemical changes:
- Growth of a plant
- Rusting of iron
- Cooking of food
- Digestion of food
- Burning of candle
Post a Comment