20 Questions
What common feature is shared by all the situations of daily life mentioned (e.g., milk left at room temperature, grapes getting fermented)?
The nature and identity of the initial substance change.
What safety precaution is recommended for Activity 1.1?
Wear suitable eyeglasses.
Why is it necessary to clean the magnesium ribbon with sandpaper before burning?
To remove the oxide layer.
What do you collect in the watch glass during Activity 1.1?
Magnesium oxide.
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.
Which of the following indicates a chemical reaction during Activity 1.1?
Change in color and the emission of light.
What are the reactants in the word-equation for the burning of magnesium ribbon?
Magnesium and oxygen
What new substance is formed when magnesium burns?
Magnesium oxide
Where are the reactants written in a word-equation?
On the left-hand side
Which observation DOES NOT indicate a chemical reaction?
Melting of ice
What does the law of conservation of mass state about a chemical reaction?
Mass can neither be created nor destroyed
How is the direction of the reaction indicated in a word-equation?
By a single-headed arrow pointing towards the products
Which of the following is the balanced chemical equation for the burning of magnesium?
$2Mg + O_2 ightarrow 2MgO$
What change is observed in the gas cylinder during Activity 1.3?
Evolution of gas
What does a chemical equation represent?
The representation of a chemical reaction
What must be the same on both sides of a balanced chemical equation?
The number of atoms of each element
Why is Eq. (1.3) considered unbalanced?
The number of atoms of each element is not the same on both sides
According to the law of conservation of mass, what remains the same during a chemical reaction?
The total mass of elements
Which equation represents the reaction between zinc and sulfur?
$Zn + S \longrightarrow ZnS$
How many oxygen atoms are on the reactant side of the unbalanced equation $Zn + S \longrightarrow ZnSO_4 + H_2$?
0
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.
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.
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