NCERT solutions for Science Exploration [English] Class 9 chapter 5 - Exploring Mixtures and their Separation [Latest edition]

Why do suspended particles settle in muddy water over time but not in milk?

How is evaporation different from boiling?

Why do you see bright rays of sunlight when it passes through small gaps between the leaves of a dense tree?

A common talcum powder contains 4 % m/m zinc oxide, which acts as an antiseptic. How much zinc oxide is present in 300 g of the talcum powder?

Your mother gives you a bottle of orange juice concentrate to mix with water and serve it to your visiting friends. She asks you to mix two tablespoons of the concentrate with water in a glass tumbler. If each tablespoon measures 15 mL and you make 150 mL of juice per person, what is the % v/v of orange juice concentrate in the mixture you prepared?

Vinegar, used as a food preservative and additive, contains 5 % v/v acetic acid. Glacial acetic acid is a liquid, i.e., 100% acetic acid. If you want to make vinegar from glacial acetic acid, how would you proceed?

If a hot, saturated solution of copper sulfate is cooled rapidly in ice-cold water, smaller and less well-formed crystals will form than if it is cooled slowly at room temperature. How would you design and perform an experiment to test this hypothesis?

Hint: Prepare a hot saturated solution of copper sulfate and divide it into two equal parts.

Refer to the solubility curves given below. If equal masses of hot, saturated solutions of compounds ‘A’ and ‘B’ are cooled from 80 °C to 60 °C, which solution is likely to deposit more solid?

Will there be any change in the size of common salt crystals if the rate of evaporation is increased or decreased? Explain.

State whether the following statement is True or False. Also, correct the False statement.

Salt can be separated from a salt solution by evaporation or distillation.

State whether the following statement is True or False. Also, correct the False statement.

Distillation can be used for separation of two liquids even when these have the same boiling point.

State whether the following statement is True or False. Also, correct the False statement.

In paper chromatography, the solvent level should be above the sample spot at the beginning of the experiment.

State whether the following statement is True or False. Also, correct the False statement.

Evaporation and crystallization are the same processes.

What if two immiscible liquids of the same density are mixed in a separating funnel, how will the layers form?

Why do immiscible liquids form two separate layers in a separating funnel?

Is sublimation different from evaporation? Justify.

Clouds are made up of tiny water droplets or ice crystals floating in the air. Based on what you know about solutions, suspensions and colloids, what type of mixture do you think clouds are and why?

Why do cities with a lot of smoke and dust in the air often look hazy?

Which of the following mixtures are correctly classified as homogeneous (Hm) and heterogeneous (Ht)? Choose the correct option.

Choose the correct options, and explain the reason for the correct and incorrect options.

Which among the following mixtures show the Tyndall Effect? A mixture of:

1. air and dust particles
2. copper sulfate and water
3. starch and water
4. acetone and water

A mixture can be categorised as a solution, a suspension, or a colloid, each possessing distinct properties. Utilise the words or phrases provided in the box to fill in the Table. Words and phrases may be used more than once.

Complete the Table.

Solve the following problem:

A cake recipe uses dry ingredients, namely 75 g of sugar for 420 g of all-purpose flour and 5 g of sodium hydrogencarbonate. Express the concentration of each component in the mixture using an appropriate method.

A brass alloy contains 70% copper by mass. Calculate the quantities of copper and zinc present in 120 g of brass.

The label on a cooking oil pack says one litre (910 g). If this oil is mixed with water, will it form a separate layer? If so, which substance will be on top? How will you separate the two layers? Also, draw the diagram of the apparatus used.

Assertion (A): Solutions do not exhibit the Tyndall effect.

Reason (R): The particles in solutions are larger than 100 nm, so they cannot scatter light.

Choose the correct option:

How would you separate the mixtures given in the Table? Mention the reason for choosing your method. If a mixture cannot be separated, explain why.

Two miscible liquids, A and B, are present in a mixture. The boiling point of A is 60°C and the boiling point of B is 90°C. Suggest a method to separate them. Also, draw a labelled diagram of the method suggested.

Compare evaporation, crystallization and distillation. In which situation, would you prefer each of these over the others?

Blood is an example of a colloidal mixture. What would happen if blood behaved like a true suspension inside the body?

Blood is an example of a colloidal mixture. In a blood sample, identify the dispersed phase and the dispersion medium.

You are given a mixture of sand, common salt and naphthalene (Fig. a). The Fig. b depicts various steps used to separate the components of this mixture. Identify and write down the correct sequence of separation techniques.

Why is distillation an effective method for separating a mixture of water and acetone?

Answer the following questions with the help of the data given in the Table.

1. What mass of potassium nitrate would be needed to prepare its saturated solution in 50 g of water at 40°C?
2. A student makes a saturated solution of potassium chloride in water at 80°C and leaves the solution to cool at room temperature (25°C). What would she observe as the solution cools? Explain.
3. What is the effect of a change in temperature on the solubility of salts? Also, compare the changes in the solubility of the four given salts with increasing temperature from 10°C to 80°C.

Three students, A, B and C, are preparing sugar solutions for an experiment:

• Student A dissolves 20 g of sugar in 80 g of water.
• Student B dissolves 20 g of sugar in 100 g of water.
• Student C dissolves 30 g of sugar in 80 g of water.

(i) Calculate the mass percentage (% m/m) concentration of sugar in each student’s solution.

(ii) Whose solution is the most concentrated? Explain why.

Examine the Fig.

1. Identify the separation technique marked as ‘S’.
2. Label the apparatus A, B and C.
3. Which of the following mixtures can be separated by the technique identified above? Use the data given in the Table. Mixtures:
   1. water - acetone
   2. water - salt
   3. acetone - alcohol
   4. sand - salt
   5. alcohol - chloroform
   6. alcohol - benzene

Demonstrate the Tyndall effect using different colloids. Create a series of experiments showcasing how light scatters in colloids making the beam visible. Use laser pointers (Safety first: Use it under the supervision of an adult), flashlights, or other light sources for your demonstrations.

Make crystals of different compounds (common salt, epsom salt, sugar, borax, nickel sulfate, etc.). Observe them under a magnifying glass or a microscope. Note down their colours and shapes.

Do red leaves also contain green pigments? Investigate it using paper chromatography.

You can try chromatography to find the number of components present in a food colour (green, orange, yellow, etc.) or in coloured mouth fresheners (fennel seeds).

Design an educational game where players identify and apply separation techniques to different mixtures through interactive challenges and hands-on activities.

If you are camping outdoors and running short on clean water, you can obtain clean water by distillation. Can you think of a set-up with the items available to you?

Can we create artificial blood that works just as real blood for all patients?