Class 10 Science Chapter 1: Chemical Reactions and Equations Quiz and Flashcards

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Questions and Answers

What common feature is shared by all the situations of daily life mentioned (e.g., milk left at room temperature, grapes getting fermented)?

The physical state of the substance changes.

The nature and identity of the initial substance change. (correct)

The temperature of the substance increases.

The substances dissolve in water.

What safety precaution is recommended for Activity 1.1?

Wear suitable eyeglasses. (correct)

Use a face mask.

Wear gloves.

Stand under a fume hood.

Why is it necessary to clean the magnesium ribbon with sandpaper before burning?

To remove the oxide layer. (correct)

To remove moisture.

To make it shiny.

To cut it into smaller pieces.

What do you collect in the watch glass during Activity 1.1?

Magnesium oxide. Signup and view all the answers

In the context of chemical reactions, what does it mean when 'the nature and the identity of the initial substance change'?

The initial substance transforms into one or more different substances. Signup and view all the answers

Which of the following indicates a chemical reaction during Activity 1.1?

Change in color and the emission of light. Signup and view all the answers

What are the reactants in the word-equation for the burning of magnesium ribbon?

Magnesium and oxygen Signup and view all the answers

What new substance is formed when magnesium burns?

Magnesium oxide Signup and view all the answers

Where are the reactants written in a word-equation?

On the left-hand side Signup and view all the answers

Which observation DOES NOT indicate a chemical reaction?

Melting of ice Signup and view all the answers

What does the law of conservation of mass state about a chemical reaction?

Mass can neither be created nor destroyed Signup and view all the answers

How is the direction of the reaction indicated in a word-equation?

By a single-headed arrow pointing towards the products Signup and view all the answers

Which of the following is the balanced chemical equation for the burning of magnesium?

$2Mg + O_2 ightarrow 2MgO$ Signup and view all the answers

What change is observed in the gas cylinder during Activity 1.3?

Evolution of gas Signup and view all the answers

What does a chemical equation represent?

The representation of a chemical reaction Signup and view all the answers

What must be the same on both sides of a balanced chemical equation?

The number of atoms of each element Signup and view all the answers

Why is Eq. (1.3) considered unbalanced?

The number of atoms of each element is not the same on both sides Signup and view all the answers

According to the law of conservation of mass, what remains the same during a chemical reaction?

The total mass of elements Signup and view all the answers

Which equation represents the reaction between zinc and sulfur?

$Zn + S \longrightarrow ZnS$ Signup and view all the answers

How many oxygen atoms are on the reactant side of the unbalanced equation $Zn + S \longrightarrow ZnSO_4 + H_2$?

0 Signup and view all the answers

Study Notes

Chemical Reactions and Equations

Chemical reactions occur in daily life, such as milk spoiling, grapes fermenting, iron rusting, food cooking, respiration, and digestion.
A chemical reaction involves a change in the nature and identity of the initial substance.
A chemical reaction can be described in a sentence form, but it can be written in a shorter form using a word-equation.

Chemical Equations

A word-equation is a simple way to describe a chemical reaction, with reactants on the left-hand side and products on the right-hand side, separated by an arrow.
The reactants are the substances that undergo chemical change, and the products are the new substances formed.
The arrowhead points towards the products, showing the direction of the reaction.

Observations of Chemical Reactions

Changes that indicate a chemical reaction has taken place include:
- Change in state
- Change in color
- Evolution of gas
- Change in temperature

Balanced Chemical Equations

The law of conservation of mass states that mass cannot be created or destroyed in a chemical reaction, so the total mass of reactants and products must remain the same.
A chemical equation is a more precise and unambiguous representation of a chemical reaction than a word-equation.
A balanced chemical equation is one where the number of atoms of each element is the same on both sides of the arrow.
To balance a chemical equation, count and compare the number of atoms of each element on both sides of the equation.

Writing a Chemical Equation

Chemical equations are a way to represent chemical reactions.
Count and compare the number of atoms of each element on both sides of the equation to ensure balance.
If the number of atoms of each element is not the same on both sides, the equation is unbalanced.

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Description

Explore the various situations in daily life where chemical reactions occur, such as milk spoilage, fermentation, and food digestion. Understand the changes that occur in substances during these processes.