Specific heat capacity and changes of state

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Big idea: specific heat capacity and changes of state

Key concept: Change. Energy transferred equals mass times specific heat capacity times temperature change. During a phase change, energy changes particle arrangements without necessarily raising temperature.
Related concepts: Models and evidence. Use a scientific explanation to make predictions, then test it against observations.
Global context: Scientific and technical innovation. Thermal properties help choose materials for heating and cooling systems.

Thermal Expansion

When a material is heated at constant pressure, its temperature increases, volume expands, and density decreases.
Expansion occurs because molecules gain kinetic energy, vibrate/move faster, and push each other apart.
Solids expand the least, gases expand the most, and liquids are in between.
Useful applications: liquid-in-glass thermometers (liquid expands in capillary tube) and bimetallic strips (two metals expand at different rates, bending to close a circuit).
Undesirable consequences: buckling of railway tracks, road surfaces, and bridges; gaps are built in to allow expansion.

Thermal expansion diagram

Specific Heat Capacity

Internal energy is the total energy stored in a system due to particle motion (kinetic) and positions (potential).
Temperature is a measure of the average kinetic energy of particles.
Specific heat capacity (c) is the energy required to raise the temperature of 1 kg of a substance by 1 °C.
Low c → heats up/cools down quickly; high c → heats up/cools down slowly.
Equation: \Delta E = m c \Delta \θ , where \Delta E in J, m in kg, c in J/kg°C, \Delta \θ in °C.

Kinetic and potential energy of particles in a liquid

Investigating Specific Heat Capacity

Aim: determine specific heat capacity by measuring energy supplied (E = IVt) and temperature change.
Independent variable: time; dependent variable: temperature; control: material, current, voltage.
Equipment: thermometer, immersion heater, beaker/block, ammeter, voltmeter, power supply, digital balance, stopwatch.
Method: record mass, initial temperature, then heat while recording current, voltage, and temperature every 60 s for 10 min.
Calculate \Delta E = IV\Delta t and c = \Delta E / (m \Delta \θ).
Systematic errors: zero balance, account for evaporation; random errors: stir water, be consistent with fluctuating readings.

Apparatus for investigating specific heat capacity

Melting & Boiling

Fixed points of pure water: melting point = 0 °C, boiling point = 100 °C at atmospheric pressure.
During a change of state (melting/boiling), temperature remains constant even though energy is still being transferred.
Energy goes into overcoming intermolecular forces (potential energy), not increasing kinetic energy.
Boiling occurs at the boiling point throughout the liquid; melting occurs at the melting point as solid becomes liquid.
Condensation (gas→liquid) and solidification (liquid→solid) also occur at constant temperature as energy is removed.

Evaporation

Evaporation is a change from liquid to gas that occurs at any temperature and only from the surface.
More energetic molecules near the surface escape, reducing the average kinetic energy → liquid cools.
Rate of evaporation increases with: higher temperature, larger surface area, and greater air movement.
Evaporation vs boiling: evaporation at any temperature, only at surface; boiling at boiling point, throughout liquid.

Think like a scientist

Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs.
Comparison: the material heated. Outcome: the temperature rise in degrees Celsius.
Control: keep the sample mass and energy input constant. Explain why this makes the comparison fairer.
Evidence: Use a consistent method, repeated observations where appropriate and a table with labelled quantities and units. Keep unexpected results and investigate their cause.
Safety: Practical activities need teacher supervision and an appropriate risk assessment. Use the provided data or simulation where the investigation specifies it.
Inquiry task: State a testable question, predict the outcome using the science, then explain how your observations would support or challenge the prediction.

Evaluate the science

Thermal properties help choose materials for heating and cooling systems.
Heat absorbed by the container and lost to surroundings must be considered when estimating specific heat capacity.
Evaluation task: Link your conclusion to evidence, identify a limitation and suggest a specific improvement. Distinguish a measured result from an explanation of its cause.

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1.What are the upper and lower fixed points on a Celsius scale thermometer?
Easy
- AThe boiling point of pure water and the freezing point of pure water
- BThe boiling point of saturated salt solution and the freezing point of salt-water
- CThe normal temperature of the human body and the freezing point of salt-water
- DThe boiling point of pure water and absolute zero
2.Which statement best describes a metal experiencing thermal expansion?
Easy
- AThe molecules increase in size.
- BThe molecules vibrate more and move further apart.
- CThe molecules expand and become larger.
- DThe molecules decrease in density.
3.When a substance is melting, what happens to its temperature and internal energy?
Medium
- ATemperature increases, internal energy increases.
- BTemperature remains constant, internal energy increases.
- CTemperature remains constant, internal energy decreases.
- DTemperature increases, internal energy remains constant.
4.Which of the following is a correct unit for specific heat capacity?
Easy
- AJ / kg
- BJ / °C
- CJ / (kg °C)
- DJ kg °C
5.The specific heat capacity of water is 4200 J/(kg °C). How much energy is required to raise the temperature of 2.0 kg of water by 5.0 °C?
Medium
- A42000 J
- B21000 J
- C8400 J
- D16800 J
6.In an experiment to determine the specific heat capacity of a metal block, a student uses an immersion heater. Which of the following is the correct equation to calculate the energy supplied to the block?
Easy
- AE = IVt
- BE = IRt
- CE = V/It
- DE = I²Vt
7.A student investigates the cooling of water. The results show that the rate of cooling is greater when the water is hotter. Which statement explains this?
Medium
- AHotter water has a higher specific heat capacity.
- BHotter water evaporates more quickly, removing more thermal energy.
- CHotter water expands, increasing its surface area.
- DHotter water has a lower density, so it rises and cools faster.
8.Which of the following factors increases the rate of evaporation of a liquid?
Easy
- ADecreasing the temperature of the liquid
- BDecreasing the surface area of the liquid
- CIncreasing the movement of air above the liquid
- DIncreasing the humidity of the air above the liquid

Thêm câu hỏi

9.Which of the following is a difference between boiling and evaporation?
Medium
- ABoiling occurs at any temperature, evaporation only at the boiling point.
- BBoiling occurs throughout the liquid, evaporation only at the surface.
- CBoiling is a change from liquid to gas, evaporation is from solid to gas.
- DBoiling requires energy, evaporation does not.
10.Which state of matter expands the most when heated at constant pressure?
Easy
- ASolid
- BLiquid
- CGas
- DAll expand equally
11.A student measures the temperature of water as it is heated. The temperature rises steadily until it reaches 100°C, then remains constant even though heating continues. Which statement explains the constant temperature?
Medium
- AThe water is losing heat to the surroundings at the same rate as it is being heated.
- BThe energy supplied is being used to increase the kinetic energy of the water molecules.
- CThe energy supplied is being used to overcome intermolecular forces during boiling.
- DThe specific heat capacity of water becomes infinite at 100°C.
12.A student investigates how the rate of cooling of water depends on the uncovered surface area. She uses two lids: lid A leaves half the surface uncovered, lid B leaves a quarter uncovered. She finds that the water cools faster with lid A than with lid B. Which lid gives a greater rate of cooling?
Medium
- ALid A, because the temperature drops more quickly
- BLid B, because the temperature drops more quickly
- CLid A, because the temperature drops more slowly
- DLid B, because the temperature drops more slowly
13.In an experiment to determine the specific heat capacity of a metal block, a student uses an immersion heater. The energy supplied to the block is calculated using the equation E = IVt. Which additional measurements are needed to calculate the specific heat capacity?
Medium
- AMass of the block and temperature change
- BMass of the block and initial temperature
- CVolume of the block and temperature change
- DDensity of the block and initial temperature
14.A student cools water from 70 °C and records temperature every 30 seconds. The results show that the temperature difference between the water and the room decreases over time. Which statement best explains why the rate of cooling decreases?
Medium
- AThe temperature difference between the water and the surroundings decreases
- BThe water evaporates more quickly as it cools
- CThe specific heat capacity of water increases as it cools
- DThe thermometer becomes less accurate at lower temperatures
15.The fixed points on a Celsius thermometer are based on the properties of pure water. What are these fixed points?
Easy
- AThe melting point of ice and the boiling point of water
- BThe freezing point of salt water and the boiling point of water
- CAbsolute zero and the boiling point of water
- DThe melting point of ice and the normal human body temperature
16.A pure substance is heated at a constant rate. Why does its temperature remain constant during the first plateau?
Medium
- AEnergy overcomes attractions as the solid melts
- BNo energy enters the substance
- CAll particles stop moving
- DThe substance has become a gas
17.Which statement correctly describes what happens to the particles in a solid when it is heated at constant pressure?
Easy
- AThe particles vibrate more and move further apart
- BThe particles expand
- CThe particles increase in size
- DThe particles move faster and get closer together
18.In an experiment to measure the specific heat capacity of water, a student uses an immersion heater and records the temperature every 60 seconds. The student notices that the temperature does not rise immediately when the heater is switched on. What is the most likely reason?
Medium
- ASome energy is used to heat the immersion heater itself
- BThe water is evaporating
- CThe thermometer has a slow response time
- DThe power supply is fluctuating
19.
A student investigates the cooling of water in a metal can and records the following results:
Time, t (s) Temperature, θ (°C)
0 84
60 75
What is the average rate of cooling between t = 0 and t = 60 s?
Medium
- A0.15 °C/s
- B9.0 °C/s
- C0.15 °C/min
- D9.0 °C/min
20.A student states that most of the thermal energy lost by hot water in a can is by evaporation, while another student says it is by conduction through the sides. Which addition to the apparatus would best test the role of evaporation?
Medium
- APlace a lid on the can to prevent evaporation
- BWrap the can in insulation to reduce conduction
- CUse a fan to increase air movement over the surface
- DStir the water to ensure uniform temperature
21.A student plots a graph of temperature against time for cooling water. He wants to check if the rate of cooling is proportional to the temperature difference between the water and the room. What shape of graph would indicate direct proportionality?
Medium
- AA straight line through the origin when plotting cooling rate against temperature difference
- BA curve that flattens over time
- CA straight line with a negative intercept
- DA horizontal line
22.A student investigates the cooling of water and records the temperature every 30 seconds. He notices that the temperature readings are sometimes fluctuating. Which precaution would improve the accuracy of the temperature readings?
Medium
- AStir the water before taking each reading
- BUse a larger beaker
- CTake readings more frequently
- DUse a thermometer with a larger range
23.A student measures the volume of water in a measuring cylinder. To obtain an accurate reading, which precaution should be taken?
Easy
- ARead the bottom of the meniscus at eye level
- BRead the top of the meniscus at eye level
- CEstimate to the nearest 10 cm³
- DPour the water into a beaker to read the volume
24.In an experiment to measure the specific heat capacity of a metal block, a student uses an immersion heater. The student records the voltage across the heater as 12.0 V and the current as 2.5 A. The heater is switched on for 300 s. What is the energy supplied to the block?
Medium
- A9000 J
- B900 J
- C90 J
- D9000 W
25.A student investigates the cooling of water. The temperature of the water is recorded every 30 s. The results show that the rate of cooling decreases as the water temperature approaches room temperature. Which statement best explains this observation?
Medium
- AThe rate of heat loss is proportional to the temperature difference between the water and the surroundings.
- BThe specific heat capacity of water increases as it cools.
- CEvaporation stops when the water is close to room temperature.
- DThe thermometer becomes less sensitive at lower temperatures.
26.In an experiment to determine the specific heat capacity of a metal block, the following measurements are taken: mass of block = 0.50 kg, initial temperature = 20.0 °C, final temperature = 30.0 °C, energy supplied = 2000 J. What is the specific heat capacity of the metal?
Medium
- A400 J/(kg °C)
- B100 J/(kg °C)
- C40 J/(kg °C)
- D4000 J/(kg °C)
27.Which of the following is a correct precaution when reading the volume of water in a measuring cylinder?
Easy
- ARead the bottom of the meniscus at eye level.
- BRead the top of the meniscus at eye level.
- CRead the scale from above the measuring cylinder.
- DEstimate the volume to the nearest 10 cm³.
28.A student investigates the cooling of water. The temperature readings are: t=0 s, θ=84 °C; t=60 s, θ=75 °C; t=120 s, θ=70 °C; t=180 s, θ=67 °C. Which statement about the rate of cooling is correct?
Medium
- AThe rate of cooling is greater between 0 and 60 s than between 120 and 180 s.
- BThe rate of cooling is constant throughout the experiment.
- CThe rate of cooling is greater between 120 and 180 s than between 0 and 60 s.
- DThe rate of cooling is zero between 120 and 180 s.
29.In the specific heat capacity experiment, why is it important to stir the water continuously while heating?
Easy
- ATo ensure the temperature is uniform throughout the water.
- BTo increase the rate of heat transfer from the heater.
- CTo prevent the water from boiling.
- DTo reduce heat loss to the surroundings.
30.A student uses an immersion heater to heat a metal block. The power of the heater is 50 W. The block has a mass of 1.0 kg and specific heat capacity 500 J/(kg °C). How long will it take to raise the temperature of the block by 20 °C?
Medium
- A200 s
- B20 s
- C100 s
- D400 s
31.Complete the sentence.
Easy
The melting point of pure ice is ____ °C and the boiling point of pure water is ____ °C.
32.State the definition of specific heat capacity.
Easy
33.Calculate the energy needed to raise the temperature of 2.0 kg of water from 20 °C to 30 °C. The specific heat capacity of water is 4200 J/kg°C.
Easy
34.Complete the sentence about evaporation.
Medium
Evaporation occurs at ____ temperature, only from the ____ of a liquid, and causes the liquid to ____.
35.In the cooling experiment with lids A and B, lid A leaves half the surface uncovered, lid B leaves a quarter uncovered. The results show that the water cools faster with lid A. Which conclusion is supported?
Medium
- AA larger uncovered surface area increases the rate of cooling.
- BA smaller uncovered surface area increases the rate of cooling.
- CThe rate of cooling is independent of uncovered surface area.
- DLid B is a better insulator than lid A.
36.Which of the following is a controlled variable in an experiment to measure the specific heat capacity of water using an immersion heater?
Easy
- AThe potential difference across the heater.
- BThe temperature of the water.
- CThe time the heater is switched on.
- DThe mass of the water.
37.In the investigation of specific heat capacity, the student uses a digital balance to measure the mass of the water. The balance has a resolution of 0.1 g. Which mass reading is recorded to the appropriate precision?
Easy
- A250.0 g
- B250 g
- C250.00 g
- D250.1 g
38.A student repeats the cooling experiment but uses a metal can instead of a glass beaker. The results show a faster rate of cooling. Which statement explains this?
Medium
- AMetal is a better conductor of heat than glass, so more heat is lost through the sides.
- BMetal has a lower specific heat capacity than glass, so it heats up faster.
- CMetal expands more than glass, increasing the surface area.
- DMetal reflects heat back into the water, reducing heat loss.
39.In an experiment to measure the specific heat capacity of a metal block, a student uses an immersion heater. The student records the voltage across the heater as 12.0 V and the current as 2.5 A. The heater is switched on for 5 minutes. What is the energy supplied to the block?
Medium
- A9000 J
- B150 J
- C1500 J
- D900 J
40.A student investigates the cooling of water in a beaker. The temperature of the water is recorded every 30 seconds. The results show that the temperature difference between the water and the room decreases by half every 30 seconds. If the initial temperature difference is 40 °C, what is the temperature difference after 90 seconds?
Medium
- A5 °C
- B10 °C
- C20 °C
- D2.5 °C
41.Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. What is the independent variable?
Easy
- Athe temperature rise in degrees Celsius
- Bthe number of repeated trials
- Cthe scientific explanation written afterwards
- Dthe material heated
42.Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. Which observation or quantity is the dependent variable?
Easy
- Athe temperature rise in degrees Celsius
- Bthe material heated
- Cthe title given to the investigation
- Dthe number of references in the report
43.Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. Which decision best controls another factor in this comparison?
Medium
- Achange every condition for each trial
- Bkeep the sample mass and energy input constant
- Cuse a different measurement method for every result
- Drecord only results that agree with the prediction
44.Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. Why should the class repeat measurements or check multiple comparable observations?
Medium
- ATo guarantee that every systematic error disappears
- BTo make an unsupported prediction become correct
- CTo assess variation and judge how consistent the evidence is
- DTo avoid reporting results that disagree with a model
45.A class is evaluating an application of specific heat capacity and changes of state. Which statement identifies a relevant limitation?
Hard
- AAll scientific models reproduce every feature of the real world
- BOne favourable result proves that a technology has no disadvantages
- CA conclusion needs no evidence when a scientific term is used
- DHeat absorbed by the container and lost to surroundings must be considered when estimating specific heat capacity.
46.Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. Which conclusion is most justified by a controlled comparison?
Hard
- AA conclusion restricted to the tested conditions, with uncertainty and limitations stated
- BA claim that the result must hold in all possible conditions
- CA claim that alternative explanations never need testing
- DA claim based only on the most convenient observation
47.Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. Select the two practices that strengthen the validity of this comparison.
Medium
- Akeep the sample mass and energy input constant
- Bchange the measurement method whenever a result is unexpected
- Crecord the temperature rise in degrees Celsius using the same agreed procedure
- Dreport only observations that confirm the prediction
48.When evaluating evidence about specific heat capacity and changes of state, select the two scientifically defensible statements.
Hard
- AOne result proves the explanation in every situation
- BHeat absorbed by the container and lost to surroundings must be considered when estimating specific heat capacity.
- CA conclusion should state the conditions and uncertainty of the evidence
- DModels never need revision when new evidence appears
49.Design a fair investigation for this question: Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. Identify what to compare, what to record and one control.
Medium
50.Explain one use of the science in specific heat capacity and changes of state and evaluate one limitation of the evidence or application.
Hard
51.A 0.50 kg sample receives 2000 J and warms by 10° Celsius. Ignore losses. What is its specific heat capacity?
Hard
- A100 J/(kg degree Celsius)
- B400 J/(kg degree Celsius)
- C4000 J/(kg degree Celsius)
- D10000 J/(kg degree Celsius)
52.A pure substance continues to receive energy while melting at constant pressure, but its temperature stays constant. Why?
Hard
- ANo energy enters the substance
- BIts mass turns entirely into heat
- CEnergy changes particle arrangements rather than increasing their mean kinetic energy
- DAll particles stop moving during melting

Ghi chú ôn tập

## Big idea: specific heat capacity and changes of state - **Key concept: Change.** Energy transferred equals mass times specific heat capacity times temperature change. During a phase change, energy changes particle arrangements without necessarily raising temperature. - **Related concepts: Models and evidence.** Use a scientific explanation to make predictions, then test it against observations. - **Global context: Scientific and technical innovation.** Thermal properties help choose materials for heating and cooling systems. ## Thermal Expansion - When a material is heated at constant pressure, its **temperature increases**, **volume expands**, and **density decreases**. - Expansion occurs because molecules gain kinetic energy, vibrate/move faster, and push each other apart. - **Solids expand the least**, **gases expand the most**, and **liquids** are in between. - Useful applications: **liquid-in-glass thermometers** (liquid expands in capillary tube) and **bimetallic strips** (two metals expand at different rates, bending to close a circuit). - Undesirable consequences: **buckling** of railway tracks, road surfaces, and bridges; gaps are built in to allow expansion. ## Specific Heat Capacity - **Internal energy** is the total energy stored in a system due to particle motion (kinetic) and positions (potential). - Temperature is a measure of the **average kinetic energy** of particles. - **Specific heat capacity (c)** is the energy required to raise the temperature of 1 kg of a substance by 1 °C. - Low c → heats up/cools down quickly; high c → heats up/cools down slowly. - Equation: \( \Delta E = m c \Delta \theta \), where \(\Delta E\) in J, m in kg, c in J/kg°C, \(\Delta \theta\) in °C. ## Investigating Specific Heat Capacity - Aim: determine specific heat capacity by measuring energy supplied (E = IVt) and temperature change. - Independent variable: **time**; dependent variable: **temperature**; control: material, current, voltage. - Equipment: thermometer, immersion heater, beaker/block, ammeter, voltmeter, power supply, digital balance, stopwatch. - Method: record mass, initial temperature, then heat while recording current, voltage, and temperature every 60 s for 10 min. - Calculate \(\Delta E = IV\Delta t\) and \(c = \Delta E / (m \Delta \theta)\). - Systematic errors: zero balance, account for evaporation; random errors: stir water, be consistent with fluctuating readings. ## Melting & Boiling - Fixed points of pure water: **melting point = 0 °C**, **boiling point = 100 °C** at atmospheric pressure. - During a change of state (melting/boiling), **temperature remains constant** even though energy is still being transferred. - Energy goes into **overcoming intermolecular forces** (potential energy), not increasing kinetic energy. - **Boiling** occurs at the boiling point throughout the liquid; **melting** occurs at the melting point as solid becomes liquid. - **Condensation** (gas→liquid) and **solidification** (liquid→solid) also occur at constant temperature as energy is removed. ## Evaporation - Evaporation is a change from **liquid to gas** that occurs **at any temperature** and **only from the surface**. - More energetic molecules near the surface escape, reducing the average kinetic energy → **liquid cools**. - Rate of evaporation increases with: **higher temperature**, **larger surface area**, and **greater air movement**. - Evaporation vs boiling: evaporation at any temperature, only at surface; boiling at boiling point, throughout liquid. ## Think like a scientist - Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. - **Comparison:** the material heated. **Outcome:** the temperature rise in degrees Celsius. - **Control:** keep the sample mass and energy input constant. Explain why this makes the comparison fairer. - **Evidence:** Use a consistent method, repeated observations where appropriate and a table with labelled quantities and units. Keep unexpected results and investigate their cause. - **Safety:** Practical activities need teacher supervision and an appropriate risk assessment. Use the provided data or simulation where the investigation specifies it. - **Inquiry task:** State a testable question, predict the outcome using the science, then explain how your observations would support or challenge the prediction. ## Evaluate the science - Thermal properties help choose materials for heating and cooling systems. - Heat absorbed by the container and lost to surroundings must be considered when estimating specific heat capacity. - **Evaluation task:** Link your conclusion to evidence, identify a limitation and suggest a specific improvement. Distinguish a measured result from an explanation of its cause.

Melting & Boiling: Fixed points of pure water: **melting point = 0 °C**, **boiling point = 100 °C** at atmospheric pressure.
Thermal Expansion: When a material is heated at constant pressure, its **temperature increases**, **volume expands**, and **density decreases**.
Investigating Specific Heat Capacity: Aim: determine specific heat capacity by measuring energy supplied (E = IVt) and temperature change.
Specific Heat Capacity: **Internal energy** is the total energy stored in a system due to particle motion (kinetic) and positions (potential).
Evaporation: Evaporation is a change from **liquid to gas** that occurs **at any temperature** and **only from the surface**.
Designing scientific inquiries: Plan a fair comparison: Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs.
Evaluating evidence and impacts: Thermal properties help choose materials for heating and cooling systems. Heat absorbed by the container and lost to surroundings must be considered when estimating specific heat capacity.
temperature increases: When a material is heated at constant pressure, its **temperature increases**, **volume expands**, and **density decreases**.
volume expands: When a material is heated at constant pressure, its **temperature increases**, **volume expands**, and **density decreases**.
density decreases: When a material is heated at constant pressure, its **temperature increases**, **volume expands**, and **density decreases**.
Solids expand the least: **Solids expand the least**, **gases expand the most**, and **liquids** are in between.
gases expand the most: **Solids expand the least**, **gases expand the most**, and **liquids** are in between.
liquids: **Solids expand the least**, **gases expand the most**, and **liquids** are in between.
liquid-in-glass thermometers: Useful applications: **liquid-in-glass thermometers** (liquid expands in capillary tube) and **bimetallic strips** (two metals expand at different rates, bending to close a circuit).
bimetallic strips: Useful applications: **liquid-in-glass thermometers** (liquid expands in capillary tube) and **bimetallic strips** (two metals expand at different rates, bending to close a circuit).
buckling: Undesirable consequences: **buckling** of railway tracks, road surfaces, and bridges; gaps are built in to allow expansion.

Thẻ ghi nhớ

What are the upper and lower fixed points on a Celsius scale thermometer?

The boiling point of pure water and the freezing point of pure water On the Celsius scale, the upper fixed point is the boiling point of pure water (100°C) and the lower fixed point is the freezing point of pure water (0°C).

Which statement best describes a metal experiencing thermal expansion?

The molecules vibrate more and move further apart. Thermal expansion occurs because molecules vibrate more as they gain kinetic energy, causing them to push each other apart. The molecules themselves do not increase in size.

When a substance is melting, what happens to its temperature and internal energy?

Temperature remains constant, internal energy increases. During melting, energy is used to overcome intermolecular forces, so temperature stays constant while internal energy increases because potential energy increases.

Which of the following is a correct unit for specific heat capacity?

J / (kg °C) Specific heat capacity is energy per unit mass per unit temperature change, so the unit is J/(kg °C) or J/kg°C.

The specific heat capacity of water is 4200 J/(kg °C). How much energy is required to raise the temperature of 2.0 kg of water by 5.0 °C?

42000 J Using ΔE = mcΔθ = 2.0 × 4200 × 5.0 = 42000 J.

In an experiment to determine the specific heat capacity of a metal block, a student uses an immersion heater. Which of the following is the correct equation to calculate the energy supplied to the block?

E = IVt The electrical energy supplied is given by E = IVt, where I is current, V is potential difference, and t is time.

A student investigates the cooling of water. The results show that the rate of cooling is greater when the water is hotter. Which statement explains this?

Hotter water evaporates more quickly, removing more thermal energy. At higher temperature, more energetic molecules escape by evaporation, removing more thermal energy, so the rate of cooling is greater.

Which of the following factors increases the rate of evaporation of a liquid?

Increasing the movement of air above the liquid Increased air movement carries away water vapour, replacing it with drier air, which increases the rate of evaporation.

Which of the following is a difference between boiling and evaporation?

Boiling occurs throughout the liquid, evaporation only at the surface. Boiling happens throughout the liquid (bubbles form), while evaporation occurs only at the surface.

Which state of matter expands the most when heated at constant pressure?

Gas Gases expand the most because their particles have high energy and can completely overcome intermolecular forces, allowing them to move apart significantly.

A student measures the temperature of water as it is heated. The temperature rises steadily until it reaches 100°C, then remains constant even though heating continues. Which statement explains the constant temperature?

The energy supplied is being used to overcome intermolecular forces during boiling. At boiling point, additional thermal energy goes into overcoming intermolecular forces (potential energy), not increasing kinetic energy, so temperature remains constant.

A student investigates how the rate of cooling of water depends on the uncovered surface area. She uses two lids: lid A leaves half the surface uncovered, lid B leaves a quarter uncovered. She finds that the water cools faster with lid A than with lid B. Which lid gives a greater rate of cooling?

Lid A, because the temperature drops more quickly A larger uncovered surface area allows more evaporation, so lid A (half uncovered) cools the water faster than lid B (quarter uncovered).

In an experiment to determine the specific heat capacity of a metal block, a student uses an immersion heater. The energy supplied to the block is calculated using the equation E = IVt. Which additional measurements are needed to calculate the specific heat capacity?

Mass of the block and temperature change Specific heat capacity c = ΔE/(mΔθ). ΔE is found from IVt, so mass m and temperature change Δθ are required.

A student cools water from 70 °C and records temperature every 30 seconds. The results show that the temperature difference between the water and the room decreases over time. Which statement best explains why the rate of cooling decreases?

The temperature difference between the water and the surroundings decreases The rate of heat transfer depends on the temperature difference between the object and its surroundings. As the water cools, this difference decreases, so the rate of cooling decreases.

The fixed points on a Celsius thermometer are based on the properties of pure water. What are these fixed points?

The melting point of ice and the boiling point of water The upper fixed point is the boiling point of pure water (100 °C) and the lower fixed point is the melting point of pure ice (0 °C).

A pure substance is heated at a constant rate. Why does its temperature remain constant during the first plateau?

Energy overcomes attractions as the solid melts During melting, energy changes the particle arrangement by overcoming attractions rather than increasing average kinetic energy.

How would you design the inquiry for specific heat capacity and changes of state?

Use a teacher-provided heating dataset to compare temperature changes for equal masses of different materials given equal energy inputs. Compare the material heated; record the temperature rise in degrees Celsius; keep the sample mass and energy input constant.

What limitation matters when applying specific heat capacity and changes of state?

Heat absorbed by the container and lost to surroundings must be considered when estimating specific heat capacity.

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Time, t (s)	Temperature, θ (°C)
0	84
60	75