Physical and chemical change
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1.Which of the following is an example of a physical change?
Easy- ABurning wood
- BRusting iron
- CMelting ice
- DCooking an egg
2.A chemical change always produces a new substance with different properties from the original.
EasyTrue or false?
3.Which of the following is NOT a typical indicator of a chemical reaction?
Medium- AChange in colour
- BFormation of a gas
- CChange in state (e.g., melting)
- DTemperature change
4.Match each type of change with its correct example.
Easy- Physical change
- Chemical change
- Burning paper
- Breaking a glass
5.Arrange the following steps in the correct order for a chemical reaction to occur, according to collision theory: (a) Product formation, (b) Effective collision, (c) Reactant particles collide, (d) Activation energy is reached.
Medium- Reactant particles collide
- Activation energy is reached
- Effective collision
- Product formation
6.Which of the following changes is a chemical change?
Easy- ADissolving sugar in water
- BChopping wood
- CBurning natural gas
- DMelting chocolate
7.Which of the following is an example of an endothermic reaction?
Medium- ABurning wood
- BNeutralisation of acid and base
- CPhotosynthesis
- DRusting of iron
8.During a chemical reaction, the total mass of the reactants equals the total mass of the products.
EasyTrue or false?
Thêm câu hỏi
9.Match each description of a change with the correct type of change.
Medium- A change that produces a new substance
- A change that only alters state or shape
- A change that absorbs heat from the surroundings
- A change that releases heat to the surroundings
- Chemical change
- Physical change
- Endothermic reaction
- Exothermic reaction
10.Arrange the following steps in the correct order for a chemical reaction to occur according to collision theory.
Hard- Reactant particles collide with sufficient energy
- Product formation
- Reactant particles approach each other
- Bonds in reactants break and new bonds form
11.Which of the following are indicators that a chemical reaction may have occurred? (Select all that apply)
Medium- AA gas is produced
- BA precipitate forms
- CThe substance changes state
- DA colour change occurs
- EThe temperature changes without external heating
12.Melting ice is an example of a chemical change.
EasyTrue or false?
13.Which of the following is a physical change?
Easy- ABurning a match
- BDissolving sugar in water
- CRusting a nail
- DCooking an egg
14.During a chemical reaction, the total mass of the reactants equals the total mass of the products. This is known as the law of
Easy- Aconservation of energy
- Bconservation of mass
- Cdefinite proportions
- Dmultiple proportions
15.A student observes that when a colourless solution of silver nitrate is added to a colourless solution of sodium chloride, a white solid forms. Which indicator of a chemical reaction is demonstrated?
Medium- ATemperature change
- BGas production
- CPrecipitate formation
- DColour change
16.Burning wood is an example of a physical change.
EasyTrue or false?
17.Which of the following are indicators that a chemical reaction has occurred? (Select all that apply)
Medium- AA change in colour
- BA change in state (e.g., melting)
- CFormation of a gas
- DA change in temperature without external heating or cooling
- EDissolving sugar in water
18.Match each description on the left with the correct type of change on the right.
Medium- Iron rusting
- Ice melting
- Baking a cake
- Cutting paper
- Physical change
- Chemical change
19.Place the following events in the correct order for a chemical reaction to occur according to collision theory.
Medium- Effective collision
- Reactant particles collide
- Products form
- Activation energy is reached
20.A student mixes two solutions and observes that the mixture becomes warm. Which type of reaction is this?
Medium- AExothermic
- BEndothermic
- CPhysical change
- DNeutralisation
21.A student mixes a clear solution of lead(II) nitrate with a clear solution of potassium iodide. A bright yellow solid forms. Which indicator of a chemical reaction is observed?
Medium- AColour change
- BFormation of a precipitate
- CGas production
- DTemperature change
22.In a chemical reaction, the total mass of the reactants is 50.0 g. After the reaction, the products are collected and their total mass is found to be 48.5 g. Which statement best explains this discrepancy?
Hard- AMass was lost because the reaction was endothermic
- BA gas was produced that escaped into the atmosphere
- CThe law of conservation of mass does not apply to chemical reactions
- DThe reaction was incomplete and some reactants remained
23.Dissolving sugar in water is an example of a chemical change.
EasyTrue or false?
24.A student performs an experiment where dilute hydrochloric acid is added to a sample of sodium hydrogencarbonate. Bubbles are observed and the mixture becomes colder. Which conclusions can be drawn?
Medium- AA gas is produced and the reaction is exothermic
- BA gas is produced and the reaction is endothermic
- CA precipitate is formed and the reaction is exothermic
- DA precipitate is formed and the reaction is endothermic
25.A physical change results in the formation of new substances.
EasyTrue or false?
26.In a chemical reaction, the total mass of the reactants equals the total mass of the products.
EasyTrue or false?
27.Which of the following is a chemical change?
Easy- AMelting ice
- BBoiling water
- CRusting iron
- DCutting paper
28.Which of the following is NOT an indicator of a chemical reaction?
Easy- AFormation of a gas
- BChange in state (e.g., solid to liquid)
- CTemperature change
- DColour change
29.Match each description with the correct type of change.
Medium- Ice melting
- Iron rusting
- Sugar dissolving in water
- Wood burning
- Physical change
- Chemical change
30.Place the following steps in the correct order for a chemical reaction to occur according to collision theory.
Medium- Reactant particles collide with sufficient energy
- Bonds in reactants break
- New bonds form to create products
- Effective collision occurs
31.A student mixes two colourless solutions and observes that the mixture becomes warm and a yellow solid forms. Which indicators of a chemical reaction are present?
Medium- ATemperature change only
- BPrecipitate formation only
- CBoth temperature change and precipitate formation
- DNeither temperature change nor precipitate formation
32.Which of the following are exothermic reactions? (Select all that apply)
Medium- ACombustion of methane
- BPhotosynthesis
- CRespiration
- DMelting ice
- ENeutralisation of acid and base
33.Match each example with the correct type of energy change.
Medium- Burning wood
- Electrolysis of water
- Rusting of iron
- Melting ice
- Exothermic
- Endothermic
34.A student adds a piece of zinc metal to hydrochloric acid. Bubbles of gas are produced and the test tube becomes warm. Which of the following is a correct conclusion?
Medium- AA physical change occurred because the zinc dissolved.
- BA chemical change occurred, indicated by gas production and temperature increase.
- COnly a temperature change occurred, so it is a physical change.
- DNo change occurred because zinc is a metal.
35.Which of the following are exothermic processes? (Select all that apply)
Medium- ABurning wood
- BMelting ice
- CRespiration in cells
- DEvaporation of water
- EReaction of sodium with water
36.When a solid dissolves in water, it is always a chemical change.
EasyTrue or false?
37.A student heats copper(II) sulfate pentahydrate (blue crystals) in a test tube. The crystals turn white and water droplets appear on the sides of the test tube. Which statement best describes this change?
Medium- AIt is a physical change because the water evaporates.
- BIt is a chemical change because a colour change occurs and water is produced.
- CIt is a physical change because the copper sulfate can be rehydrated to blue crystals.
- DIt is a chemical change because heat is absorbed.
38.A student adds a piece of zinc to dilute hydrochloric acid. Bubbles of gas are produced and the test tube becomes warm. Which of the following is a correct conclusion?
Medium- AOnly a physical change has occurred because a gas is produced.
- BA chemical change has occurred because a gas is produced and there is a temperature change.
- COnly a physical change has occurred because the temperature increased.
- DA chemical change has occurred because the temperature increased, but the gas production is not a sign of a chemical change.
39.Which of the following is a sign that a chemical reaction has occurred?
Easy- AThe substance changes state
- BA gas is produced
- CThe substance dissolves
- DThe shape changes
40.In a chemical reaction, atoms are rearranged and new substances are formed.
EasyTrue or false?
41.What is the term for a reaction that releases heat?
Easy42.Complete the sentence.
EasyIn a chemical reaction, the substances that react are called ____ and the new substances formed are called ____.
43.In an exothermic reaction, the temperature of the surroundings increases by 15°C. If the initial temperature was 20°C, what is the final temperature?
Easy44.Name the process by which a solid forms from a solution during a chemical reaction.
Easy45.In an experiment, 12 g of magnesium is burned in air to form magnesium oxide. The product has a mass of 20 g. What mass of oxygen from the air combined with the magnesium?
Medium46.What is the term for a reaction that absorbs heat from the surroundings?
Easy47.In an exothermic reaction, the temperature of 100 mL of water increases from 20°C to 35°C. Assuming no heat loss, calculate the heat energy released (specific heat capacity of water = 4.18 J/g°C, density of water = 1 g/mL).
Hard48.A student burns 2.4 g of magnesium in air. The magnesium reacts with oxygen to form magnesium oxide. If the mass of magnesium oxide produced is 4.0 g, what mass of oxygen reacted?
Medium49.What is the name for a reaction that releases heat?
Easy50.Complete the sentence about indicators of chemical change.
MediumThree indicators that a chemical reaction has occurred are ____ change, formation of a ____, and evolution of a ____.
51.What term describes the minimum energy required for a chemical reaction to occur?
Easy52.In an exothermic reaction, the temperature of 50 mL of water increases from 22°C to 37°C. Assuming no heat loss, calculate the heat energy released. (Specific heat capacity of water = 4.18 J/g°C; density of water = 1 g/mL)
Medium53.Explain why the combustion of methane (CH4 + 2O2 → CO2 + 2H2O) is a chemical change.
Medium54.Explain why the electrolysis of water (H₂O → H₂ + O₂) is a chemical change.
Medium55.Explain why the electrolysis of water is a chemical change.
Medium56.Explain why the combustion of methane (CH₄ + 2O₂ → CO₂ + 2H₂O) is a chemical change.
Medium57.In an exothermic reaction, the temperature of the surroundings increases by 15°C. If the initial temperature was 20°C, what is the final temperature?
Easy- A35 °C
- B31 °C
- C43 °C
- D39 °C
58.In an experiment, 12 g of magnesium is burned in air to form magnesium oxide. The product has a mass of 20 g. What mass of oxygen from the air combined with the magnesium?
Medium- A7 g
- B10 g
- C8 g
- D9 g
59.In an exothermic reaction, the temperature of 100 mL of water increases from 20°C to 35°C. Assuming no heat loss, calculate the heat energy released (specific heat capacity of water = 4.18 J/g°C, density of water = 1 g/mL).
Medium- A6897 J
- B5643 J
- C7524 J
- D6270 J
60.A student burns 2.4 g of magnesium in air. The magnesium reacts with oxygen to form magnesium oxide. If the mass of magnesium oxide produced is 4.0 g, what mass of oxygen reacted?
Medium- A3.6 g
- B2.6 g
- C0.6 g
- D1.6 g
61.In an exothermic reaction, the temperature of 50 mL of water increases from 22°C to 37°C. Assuming no heat loss, calculate the heat energy released. (Specific heat capacity of water = 4.18 J/g°C; density of water = 1 g/mL)
Medium- A3135 J
- B3763 J
- C3449 J
- D2821 J
Thẻ ghi nhớ
What is a physical change?
A change that alters the form or appearance of a substance but does not change its chemical composition. Examples include melting, freezing, and dissolving.
What is a chemical change?
A process that transforms one set of chemical substances into another, involving the rearrangement of atoms and breaking/forming of chemical bonds. New products with different properties are formed.
List four indicators that a chemical reaction has occurred.
Gas production, formation of a precipitate, colour change, and temperature change (heat released or absorbed).
What are reactants?
The substances initially involved in a chemical reaction. They are consumed to form products.
What are products?
The new substances formed as a result of a chemical reaction. They have properties different from the reactants.
What does a chemical equation represent?
A symbolic representation of a chemical reaction, showing the reactants, products, and sometimes reaction conditions and intermediate products.
Define exothermic reaction.
A chemical reaction that releases heat energy to the surroundings. The temperature of the surroundings increases.
Define endothermic reaction.
A chemical reaction that absorbs heat energy from the surroundings. The temperature of the surroundings decreases.
How does increasing temperature affect reaction rate?
It increases the reaction rate because more thermal energy is available to reach the activation energy needed for bond breaking.
What is activation energy?
The minimum energy required for a chemical reaction to occur. It is needed to break bonds in the reactants.
What is a redox reaction?
A reaction involving oxidation (loss of electrons) and reduction (gain of electrons). Examples include combination, decomposition, and single displacement reactions.
What is a non-redox reaction?
A chemical reaction where no oxidation or reduction occurs; no change in oxidation states of atoms.
What is a combination reaction?
A reaction where two or more substances combine to form a single product. Example: 2H₂ + O₂ → 2H₂O.
What is a decomposition reaction?
A reaction where a single compound breaks down into two or more simpler substances. Example: 2H₂O → 2H₂ + O₂.
What is a single displacement reaction?
A reaction where one element replaces another in a compound. Example: Zn + CuSO₄ → ZnSO₄ + Cu.
What is a precipitate?
A solid that forms from a solution during a chemical reaction. It is an indicator of a chemical change.
Give an example of a physical change.
Melting an ice cube – the water changes state but remains H₂O.
Give an example of a chemical change.
Burning wood – wood reacts with oxygen to produce ash, carbon dioxide, and water, forming new substances.
What is a catalyst?
A substance that increases the rate of a chemical reaction without being consumed in the process. Enzymes are biological catalysts.
What is a metabolic pathway?
A series of consecutive chemical reactions where the product of one reaction is the reactant of the next, often catalyzed by enzymes.
What did Antoine Lavoisier discover about combustion?
He showed that combustion is a reaction with oxygen from the air, disproving the phlogiston theory.
What is the law of definite proportions?
A chemical compound always contains the same proportion of elements by mass, regardless of the source. This led to stoichiometry.
What was significant about Friedrich Wöhler's synthesis of urea in 1828?
It disproved vitalism by showing that an organic compound (urea) could be synthesized from inorganic precursors.
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