Term 1 - Week 1
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A chemical reaction happens when substances called reactants change into new substances called products. During this process, atoms rearrange and form new combinations. The new substances usually have different properties from the original materials.
Matter can undergo two kinds of changes: Physical change and Chemical change
Physical Change
Physical Change
A physical change affects only the appearance, shape, or state of matter. No new substance is formed. (e.g. Melting ice, Cutting paper, Boiling water, Dissolving sugar in water) The substance remains the same even after the change
Chemical Change
Chemical Change
A chemical change produces a new substance with new properties. This change is often difficult to reverse. (e.g. Burning wood, Cooking food, Rusting iron, and Spoiling milk). During a chemical change, chemical reactions occur.
Phase of Matter
Phase of Matter
Matter also exists in different phases known as solid, liquid, and gas. Solids have a definite shape and volume because their particles are tightly packed together. Examples of solids include ice, wood, and metal spoons. Liquids have a definite volume but no definite shape because they take the shape of their container. Water, juice, and oil are examples of liquids. Gases have neither definite shape nor definite volume because their particles move freely. Oxygen, steam, and carbon dioxide are examples of gases.
Matter can change from one phase to another through heating or cooling. Melting changes a solid into a liquid, freezing changes a liquid into a solid, evaporation changes a liquid into gas, and condensation changes gas into liquid. These changes are physical changes because no new substance is formed.
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DAY 1: Identify the observable indicators of a chemical reaction such as color change, formation of a precipitate, release of gas or odor, and change in temperature
Evidence of Chemical Reaction
Chemical reactions show observable signs called evidences or indicators. One indicator is color change. For example, iron turns reddish-brown when rust forms, and sliced apples become brown after exposure to air. Another indicator is the formation of a precipitate, which is a solid produced when two liquids react. Mixing silver nitrate and sodium chloride forms a white solid called silver chloride. The release of gas is another sign of chemical reaction and is often seen as bubbles or fizzing. Vinegar reacting with baking soda releases carbon dioxide gas. Temperature change is also an indicator because some reactions release heat while others absorb heat. Burning fuel releases heat, while instant cold packs absorb heat. Production of odor can also indicate a chemical reaction, such as the foul smell of spoiled eggs or rotten food.
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DAY 2: Explain how the observable indicators show that a chemical reaction has occurred.
How Chemical Reaction Occurs
How Chemical Reaction Occurs
Observable indicators provide evidence that a chemical reaction has occurred because they show that new substances have been formed. Common signs include a change in color, the production of gas (seen as bubbles), the formation of a solid called a precipitate, a change in temperature without external heating or cooling, and the release of light or a new odor. These changes happen because the atoms in the reacting substances rearrange to create different substances with new physical and chemical properties. Although one sign alone does not always confirm a chemical reaction, the presence of one or more of these observable indicators strongly suggests that a chemical change has taken place.
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DAY 3: Identify common acids, bases, and salts such as hydrochloric acid, sodium hydroxide, and saline solution using different indicators.
Acid, Base, and Salt
Acid, Base, and Salt
Chemical substances can be classified as acids, bases, and salts based on their properties and behavior in water. Acids release hydrogen ions (H⁺) in aqueous solutions, have a sour taste, and usually have a pH lower than 7. Examples include hydrochloric acid, vinegar, and citric acid. Bases release hydroxide ions (OH⁻) in water, feel slippery, taste bitter, and have a pH higher than 7. Examples include sodium hydroxide, ammonia, and soap. Salts are formed through the neutralization of acids and bases and may be neutral, acidic, or basic depending on their composition. Common examples include table salt and saline solution.
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Day 4: Differentiate acids, bases, and salts based on their properties and examples
Acids have a pH below 7, turn blue litmus paper red, are often corrosive, react with certain metals to produce hydrogen gas, and conduct electricity when dissolved in water. Bases have a pH above 7, turn red litmus paper blue, feel slippery, are often caustic, and also conduct electricity in aqueous solutions. Salts are usually crystalline solids with high melting points, are often soluble in water, conduct electricity when dissolved or molten, and may be neutral, acidic, or basic depending on their composition
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Day 5: Identify common acids, bases, and salts using natural indicators from vegetables (e.g., red cabbage and carrots) through a simple investigation.
Common acids, bases, and salts can be identified using natural indicators extracted from vegetables such as red cabbage and carrots. During a simple investigation, these natural indicators change color when mixed with different substances. Acidic solutions produce one color, basic solutions produce another, while neutral solutions such as many salts show little or no color change. By observing and comparing these color changes, the nature of an unknown substance can be identified as an acid, base, or salt.
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