Skip to content
CNMS ICSE - 7 Std
Share
Explore

Question Paper

Answer key

Chapter: 03. Elements Compounds And Mixtures

⁠

Grade 7 Science Practice Exam Paper

Chapter: Elements, Compounds and Mixtures

Time Allowed: 2 Hours ​Maximum Marks: 50
⁠

Section A: Multiple Choice Questions (MCQs)

Choose the correct option for each of the following questions. (5 × 1 = 5 Marks)
Which of the following is a homogeneous solid mixture of copper and tin?
(a) Steel
(b) Brass
(​c​) Bronze
(d) Iron sulphide
In a molecule of water (H₂O), the constituent elements hydrogen and oxygen are present in a fixed proportion by mass of:
(a) 1 : 8
(b) 8 : 1
(​c​) 1 : 2
(d) 2 : 1
The symbol of which of the following elements is derived from its Latin name Plumbum?
(a) Potassium
(b) Mercury
(​c​) Tin
(d) Lead
Which separation method is most suitable when one component of a solid-solid mixture is heavier than water and the other is lighter than water (e.g., sand and sawdust)?
(a) Sublimation
(b) Gravitation
(​c​) Winnowing
(d) Filtration
Rectified spirit is a mixture obtained from the fractional distillation of ethanol and water. It consists of:
(a) 95% water and 5% alcohol
(b) 50% water and 50% alcohol
(​c​) 95% alcohol and 5% water
(d) 100% pure alcohol
⁠

Section B: Fill in the Blanks

Fill in the blanks with appropriate words. Use the exact blank format specified. (5 × 1 = 5 Marks)
The chemical breakdown of a compound due to its reaction with water is known as _ _ _ _ _ _ _ _ _ _ _ _ _ _.
Gaseous elements that do not react chemically with other elements are called _ _ _ _ _ _ _ _ _ _ _ _ _ _.
A homogeneous solid mixture of two or more metals, or a metal and a small amount of non-metal, is called an _ _ _ _ _ _ _ _ _ _ _ _ _ _.
In paper chromatography, a specially designed paper made of cellulose called _ _ _ _ _ _ _ _ _ _ _ _ _ _ filter paper is used as the stationary phase.
The process during which a vapour or gas directly changes into its solid state on cooling is called _ _ _ _ _ _ _ _ _ _ _ _ _ _.
⁠

Section C: True or False Questions

State whether the following statements are True or False. (5 × 1 = 5 Marks)
Generally, energy is either released or absorbed during the physical formation of a mixture. (________)
Non-metals are generally soft, non-lustrous, brittle, and are bad conductors of heat and electricity. (________)
The constituent elements of a compound can be easily separated using simple physical methods. (________)
Brass is an alloy made of a homogeneous mixture of copper and zinc. (________)
Chromatography is used in sports to test athletes for performance-enhancing drugs. (________)
⁠

Section D: Explanations of Terms

Define and explain the following terms in one or two sentences. (3 × 2 = 6 Marks)
Metalloids
Distillate
Emulsion
⁠

Section E: Complete the Series

Analyze the relationship in the first pair and complete the second pair. (3 × 1 = 3 Marks)
Sodium : Natrium :: Potassium : _ _ _ _ _ _ _ _ _ _ _ _ _ _
Sand in water : Heterogeneous mixture :: Salt in water : _ _ _ _ _ _ _ _ _ _ _ _ _ _
Iron filings and sand : Magnetic separation :: Ammonium chloride and common salt : _ _ _ _ _ _ _ _ _ _ _ _ _ _
⁠

Section F: Differentiate Between Concepts

Differentiate between the following pairs based on the parameters provided. (2 × 3 = 6 Marks)
Pure Substance vs. Impure Substance (Mixture) (On the basis of Composition and Melting/Boiling Points)
Miscible Liquids vs. Immiscible Liquids (On the basis of Solubility/Layers formed and Separation Method)
⁠

Section G: Short Answer Questions

Answer the following questions briefly. (4 × 2 = 8 Marks)
Why does steel rust less readily than pure iron? Explain its composition.
State any two characteristics of a compound.
Why does mustard oil form a separate layer on top of water when mixed?
What is the fundamental principle behind using the method of Centrifugation?
⁠

Section H: Diagram-Based Questions

Observe the diagram below and answer the questions that follow.
A laboratory setup depicting the sublimation of ammonium chloride.
⁠
⁠
⁠
Identify the separation process shown in the diagram. (1 Mark)
What is the purpose of blocking the nozzle of the inverted funnel with a cotton plug? (1 Mark)
Which substance out of the mixture remains behind in the china dish after heating is complete? (1 Mark)
⁠

Section I: Observation-Based & Everyday Use Questions

Apply your knowledge of chemistry to answer these real-life scenarios. (3 × 2 = 6 Marks)
Observation: A student heats a mixture of iron filings and sulphur powder in a test tube. A dark grey substance is formed.
(a) What is the chemical name of this dark grey substance?
(b) Will this dark grey substance be attracted to a magnet? Explain why or why not.
Everyday Use: Suppose you accidentally spill water into a container of kerosene oil. Explain step-by-step how you can safely separate the kerosene oil from the water in a laboratory.
Environmental/Health: A doctor advises a patient to consume milk with a lower fat content. Which separation technique is used in dairies to separate cream (fat) from milk? Briefly explain how it works.
⁠

Section J: Long Answer Questions

Answer the following questions in detail. (2 × 2.5 = 5 Marks)
Explain the process of separating a three-component mixture of sand, sawdust, and common salt using a flowchart or step-by-step description. Highlight the physical properties utilized at each step.
What is Paper Chromatography? Describe how you would separate the different colors of ink from a marker pen using this technique in a laboratory, explaining the principle of different solubilities.
⁠
Gallery
 
Want to print your doc?
This is not the way.
Try clicking the ··· in the right corner or using a keyboard shortcut (
CtrlP
) instead.