1. Chemistry is best described as the study of matter with special attention to its composition, structure, properties, and changes. What does this description mainly show?
ⓐ. Chemistry deals only with substances found in laboratories
ⓑ. Chemistry studies matter and its transformations
ⓒ. Chemistry is limited to naming elements and compounds
ⓓ. Chemistry avoids measurement because substances can be identified by sight
Correct Answer: Chemistry studies matter and its transformations
Explanation: Chemistry is not limited to a list of chemicals or laboratory activities. It studies what matter is made of, how particles are arranged, what properties substances show, and how substances change during reactions. Composition tells the kinds and amounts of components present in matter. Structure describes how those components are arranged. Properties and changes connect the identity of a substance with its behaviour, so measurement and observation both become central from the beginning.
2. A substance is called matter only if it satisfies two basic conditions. The pair that gives those conditions is:
ⓐ. It has colour and can dissolve in water
ⓑ. It burns and produces heat
ⓒ. It is visible and has a fixed shape
ⓓ. It has mass and occupies space
Correct Answer: It has mass and occupies space
Explanation: Matter is anything that has mass and occupies space. Mass means the substance contains a measurable amount of material, while occupying space means it has volume. Colour, solubility, burning, and shape are properties that may vary from one substance to another. Air is matter even though it is not normally visible, because it has mass and fills space. The definition of matter depends on mass and volume, not on whether a substance can be seen easily.
3. Among the following, the best everyday example of matter is:
ⓐ. Heat from a flame
ⓑ. Sound from a bell
ⓒ. Air in a tyre
ⓓ. Shadow on a wall
Correct Answer: Air in a tyre
Explanation: Air is matter because it has mass and occupies the space inside the tyre. Heat and sound are forms of energy, not matter, because they do not have mass in the ordinary chemical sense. A shadow is only a region where light is blocked, so it is not a material substance. The example also shows why matter is not restricted to solids and liquids; gases are included too. A useful distinction is that matter can be sampled as a substance, while energy and shadows describe effects or conditions.
4. A learner writes that chemistry is mainly useful because it connects substances with measurable quantities. The strongest reason supporting this idea is:
ⓐ. Chemistry ignores physical observations and uses numbers only
ⓑ. Chemical changes can be studied without identifying the substances involved
ⓒ. Many chemical ideas compare amounts, masses, volumes, and composition
ⓓ. Every chemical substance has exactly the same mass and volume
Correct Answer: Many chemical ideas compare amounts, masses, volumes, and composition
Explanation: Chemistry uses observation, but it also depends strongly on measurement. When substances react, the amount of each reactant and product matters. Later ideas such as mole, molar mass, concentration, and stoichiometry all require numerical relationships. Measurement helps convert qualitative observations into reliable chemical conclusions. Chemistry is not only about numbers, but without measured quantities, many chemical relationships cannot be tested or used accurately.
5. In a simple description of water, the words "hydrogen and oxygen are present in a definite arrangement in \(\mathrm{H_2O}\)" mainly refer to:
ⓐ. Composition and structure
ⓑ. Colour and taste
ⓒ. Cost and availability
ⓓ. Shape and size of the container
Correct Answer: Composition and structure
Explanation: Composition tells which elements are present in a substance and in what proportion. In \(\mathrm{H_2O}\), hydrogen and oxygen are the elements present. Structure refers to how atoms are arranged or connected in the substance. Colour, taste, cost, and container shape are not the main chemical meaning of the statement. This distinction helps separate the internal chemical identity of a substance from its external surroundings.
6. A sealed bottle contains sugar crystals, and a spoon contains table salt. Both are examples used in chemistry because:
ⓐ. They are substances studied only after burning in air
ⓑ. They are matter with definite chemical identity
ⓒ. They are gases under ordinary laboratory conditions
ⓓ. They cannot be measured by mass or volume
Correct Answer: They are matter with definite chemical identity
Explanation: Sugar and table salt are familiar substances, so they provide simple entry points into chemistry. Both have mass and occupy space, so both are matter. Each also has a chemical identity that can be studied through composition and properties. They are not gases at ordinary conditions, and they can certainly be measured by mass. Everyday substances become chemical examples when their composition, properties, and changes are studied scientifically.
7. Match the chemistry focus in Column I with the most suitable description in Column II.
| Column I | Column II |
|---|
| P. Composition | 1. Behaviour such as solubility, melting, or reaction tendency |
| Q. Structure | 2. Kinds and amounts of components present |
| R. Properties | 3. Rearrangement leading to a new substance |
| S. Transformation | 4. Arrangement of particles or atoms |
ⓐ. P-4, Q-2, R-1, S-3
ⓑ. P-2, Q-1, R-4, S-3
ⓒ. P-2, Q-4, R-1, S-3
ⓓ. P-3, Q-4, R-2, S-1
Correct Answer: P-2, Q-4, R-1, S-3
Explanation: Composition is about what a substance contains and in what amount. Structure refers to the arrangement of particles, atoms, or groups in a substance. Properties describe observable or measurable behaviour, such as melting point, solubility, or reactivity. Transformation means a change, especially one where substances may be converted into new substances. The pairing is useful because chemistry studies all four ideas together rather than treating substances as only names or appearances.
8. A metal wire conducts electricity, a fuel burns, and a medicine reacts in the body. These examples mainly show that chemistry studies:
ⓐ. Only harmful substances and their effects
ⓑ. Only factory-made substances and products
ⓒ. Substance properties and changes
ⓓ. Only substances that are solids at room temperature
Correct Answer: Substance properties and changes
Explanation: Conductivity is a property of the metal, burning is a chemical change involving the fuel, and the action of a medicine depends on chemical interactions in the body. These examples show that chemistry connects substances with their behaviour. Chemistry includes natural and manufactured substances, useful and harmful substances, and substances in different physical states. It is not restricted to factory products or solid materials. The same basic chemical approach can be used for metals, fuels, medicines, fertilizers, air, and water.
9. Consider the following statements about matter and chemistry:
I. Matter includes substances that have mass and occupy space.
II. Chemistry studies only substances that are visible to the naked eye.
III. Measurement helps compare chemical quantities reliably.
ⓐ. I only
ⓑ. I and II only
ⓒ. I and III only
ⓓ. II and III only
Correct Answer: I and III only
Explanation: Statement I is true because the basic definition of matter depends on mass and space occupied. Statement II is not true because gases such as air are matter even when they are not directly visible. Chemistry also studies particles and substances whose effects may be measured rather than simply seen. Statement III is true because chemical comparisons often require mass, volume, amount, or concentration. Visibility is a weak test for matter, while measurable physical presence is the stronger idea.
10. A simple investigation compares how much salt dissolves in warm water and cold water. The chemistry idea most directly involved is:
ⓐ. Salt price under different conditions
ⓑ. Solubility under different conditions
ⓒ. Container colour under different conditions
ⓓ. Spoon shape under different conditions
Correct Answer: Solubility under different conditions
Explanation: Dissolving behaviour is related to the property called solubility. Comparing warm and cold water shows how a condition can affect the behaviour of a substance. The price of salt, container colour, and spoon shape are not the central chemical variables in this observation. Chemistry often begins with such simple observations and then makes them more precise through measurement. The important point is to connect a visible behaviour with a property of matter.
11. In agriculture, fertilizers are useful chemical products because they mainly:
ⓐ. Supply needed nutrients to plants
ⓑ. Convert all soil into pure water
ⓒ. Remove the need for sunlight completely
ⓓ. Make every crop grow without limits
Correct Answer: Supply needed nutrients to plants
Explanation: Fertilizers are connected with chemistry because they contain substances that supply nutrients required for plant growth. Their usefulness depends on composition and proper use. They do not replace sunlight, water, soil conditions, or biological growth processes. Excessive or careless use can also create environmental problems, so chemical knowledge is needed for both benefit and control. Chemistry helps explain why a substance can be useful in one amount but harmful in another.
12. The statement "all chemicals are dangerous" is scientifically weak because:
ⓐ. Only medicines and laboratory acids should be called chemicals
ⓑ. Chemical risk depends on identity, amount, and use
ⓒ. Natural substances are never chemical substances
ⓓ. Chemistry deals with industry but not daily life
Correct Answer: Chemical risk depends on identity, amount, and use
Explanation: The word chemical simply refers to a substance with a chemical identity. Water, salt, sugar, medicines, fuels, and fertilizers are all connected with chemistry, but their effects are not the same. A substance may be helpful in one context and harmful in another if used carelessly or in excess. The risk depends on the substance, quantity, exposure, and conditions of use. Chemistry as knowledge helps us understand and manage substances rather than label all of them as dangerous.
13. A food label mentions added minerals, a clinic uses an antiseptic, and a factory produces plastic containers. The shared reason these are chemistry-related is:
ⓐ. They all involve only gases
ⓑ. They all prove that natural materials are never chemical substances
ⓒ. They all avoid measurement and standardization
ⓓ. They all involve substances, their composition, and their uses
Correct Answer: They all involve substances, their composition, and their uses
Explanation: Food minerals, antiseptics, and plastics are different examples, but each involves substances with particular compositions and properties. Chemistry explains why those substances behave in useful ways. The examples come from food, health, and materials, showing that chemistry appears across daily life and industry. They are not all gases, and natural materials are also made of chemical substances. Measurement and standardization help make these applications reliable and safe.
14. Use the arrangement described below: four cards are placed on a desk.
Card P: \(\mathrm{H_2O}\) in a glass
Card Q: Air inside a balloon
Card R: Light from a lamp
Card S: A piece of copper wire
Which set contains only matter?
ⓐ. P, Q, and S
ⓑ. P, R, and S
ⓒ. Q, R, and S
ⓓ. P, Q, and R
Correct Answer: P, Q, and S
Explanation: Water, air, and copper wire are all matter because each has mass and occupies space. Water is a liquid, air is a gas, and copper is a solid, so matter can appear in different physical states. Light from a lamp is energy, not a material sample with mass and volume in the ordinary chemical classification. This question also shows why matter should not be identified only by visibility or hardness. A gas may be invisible and still count as matter because it can fill a container and exert measurable effects.
15. Chemistry contributes to environmental protection most directly when it is used to:
ⓐ. Identify pollutants and design safer ways to use or treat substances
ⓑ. Remove all substances from air, water, and soil
ⓒ. Treat every artificial substance as useful and every natural substance as harmful
ⓓ. Avoid studying fuels, fertilizers, and materials
Correct Answer: Identify pollutants and design safer ways to use or treat substances
Explanation: Environmental chemistry involves understanding substances present in air, water, and soil. Chemical knowledge helps identify pollutants, measure their amounts, and design safer treatment or prevention methods. The goal is not to remove all substances, because air, water, and soil themselves contain matter. It is also not scientific to classify substances as good or bad only by whether they are natural or manufactured. The chemical identity, amount, and conditions of use decide the real effect of a substance.
16. A factory prepares glass, an energy plant handles fuels, and a hospital stores medicines under controlled conditions. These examples most clearly show that chemistry is useful in:
ⓐ. Only naming substances without using them
ⓑ. Avoiding all manufactured materials
ⓒ. Studying only substances that occur naturally
ⓓ. Industry, energy, health, and materials
Correct Answer: Industry, energy, health, and materials
Explanation: Chemistry connects the composition and properties of substances with their practical uses. Glass preparation involves materials, fuels involve energy changes, and medicines involve substances chosen for specific effects. These examples also show that chemistry is not restricted to natural substances or laboratory bottles. Industrial chemistry uses knowledge of substances to make products with controlled quality and safety. The same chemical idea can be useful in daily life and large-scale manufacturing when the identity and behaviour of matter are understood.
17. The phrase "chemistry as knowledge" is different from "chemicals as substances" because:
ⓐ. Chemistry means only harmful substances, while chemicals mean safe substances
ⓑ. Chemistry exists only in factories, while chemicals exist only in nature
ⓒ. Chemistry avoids substances and studies only light and sound
ⓓ. Chemistry is the study; chemicals are substances being studied
Correct Answer: Chemistry is the study; chemicals are substances being studied
Explanation: Chemistry is the scientific study of matter, its properties, composition, structure, and changes. Chemicals are substances, such as water, salt, oxygen, sugar, medicines, or fuels. Confusing the two can lead to the wrong idea that chemistry itself is a dangerous material. A chemical substance may be useful, harmful, or ordinary depending on its identity, amount, and conditions of use. Chemistry provides the knowledge needed to understand and manage substances, not a label that makes every substance unsafe.
18. Match each area in Column I with the most suitable chemistry-related example in Column II.
| Column I | Column II |
|---|
| P. Food | 1. Fertilizer supplying nutrients to soil |
| Q. Health | 2. Preservative or mineral content in a packaged item |
| R. Agriculture | 3. Drug or antiseptic selected for a specific use |
| S. Materials | 4. Polymer, glass, alloy, or ceramic product |
ⓐ. P-2, Q-3, R-1, S-4
ⓑ. P-3, Q-2, R-1, S-4
ⓒ. P-2, Q-1, R-3, S-4
ⓓ. P-4, Q-3, R-2, S-1
Correct Answer: P-2, Q-3, R-1, S-4
Explanation: Food chemistry includes substances such as nutrients, preservatives, flavours, and minerals. Health-related chemistry includes medicines, antiseptics, disinfectants, and substances used for diagnosis or treatment. Agriculture uses substances such as fertilizers and soil-treatment materials. Materials chemistry deals with substances such as polymers, glass, alloys, ceramics, and fibres. The pairing also shows that chemistry is spread across many fields, not confined to one kind of product.
19. A solid block of iron keeps its own shape on a table, while the same volume of water takes the shape of a beaker. This difference mainly occurs because:
ⓐ. Liquid particles have no measurable mass
ⓑ. Solid particles are more fixed in position
ⓒ. Solids are always chemically purer than liquids
ⓓ. Liquids occupy no space unless they are heated
Correct Answer: Solid particles are more fixed in position
Explanation: A solid has a definite shape because its particles are closely packed and have limited movement around fixed positions. A liquid has a definite volume but no fixed shape, so it takes the shape of the container. The difference is based on particle arrangement and movement, not on chemical purity. Both iron and water have mass and occupy space. A liquid does not lose matter-like behaviour just because it flows.
20. A gas in a syringe can be compressed noticeably when the nozzle is closed, but water in the same syringe resists compression strongly. The best particle-level explanation is:
ⓐ. Gas particles have larger empty spaces than liquid particles
ⓑ. Gas particles have no mass, so they disappear during compression
ⓒ. Liquid particles are not matter because they cannot be compressed easily
ⓓ. Gas compression changes every gas into a solid immediately
Correct Answer: Gas particles have larger empty spaces than liquid particles
Explanation: Gases are highly compressible because their particles are far apart and there is much empty space between them. When pressure is applied, the particles can be pushed closer together. Liquids have particles much closer together, so they are far less compressible. Compression changes the spacing between gas particles; it does not mean the particles vanish. This is why compressibility is a strong practical difference between gases and liquids.
