1.4 HCHEM Hwk Bar Charts WS 1.pdf - Bar Graphs Worksheet 1 For ... - Free Printable

Thank you for uploading the image. Since I cannot view images directly, I’ll rely on the text you’ve provided to solve the problem.

Based on the text you pasted, this is “Bar Graphs Worksheet 1”, which contains three main questions about energy transfer in systems — specifically, using bar graphs and pie charts to represent kinetic energy (KE), potential energy (PE), and thermal energy (E_thermal) at different points in time or positions.

Let’s go through each question step by step.

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## 🔹 Question 1: A tray of some cookies sits on a hot plate and starts to boil.

> “Before each diagram, indicate how the arrangement of the system has changed from the initial state.”

This question involves a system where cookies are on a hot plate and begin to boil — which implies they are heating up, possibly evaporating moisture or undergoing phase change. The key idea is that energy is being transferred into the system from the hot plate (external source).

We are given 3 states:

- Initial state (A): Cookies are cold/on the plate.
- State B: Some time later — cookies are warming.
- State C: Boiling begins — significant energy input, phase change occurring.

Energy types:

- KE = Kinetic energy (molecular motion → temperature)
- PE = Potential energy (chemical bonds, position — may not change much here unless something breaks apart)
- E_thermal = Thermal energy (heat content — often used interchangeably with internal energy in basic contexts)

In this context, since it’s a cooking/boiling scenario, thermal energy increases, which increases kinetic energy (molecules move faster). Potential energy might stay constant unless chemical bonds are broken (e.g., caramelization), but for simplicity, we can assume PE remains low and unchanged.

Bar graph interpretation:

You’re asked to draw bars for KE, PE, E_thermal at each state.

#### ➤ State A (initial):
- KE: Low (cold cookies)
- PE: Constant (assume no change)
- E_thermal: Low

#### ➤ State B (warming):
- KE: Higher than A
- PE: Same as A
- E_thermal: Higher than A

#### ➤ State C (boiling):
- KE: Even higher (molecules moving fast, phase change requires energy)
- PE: Possibly slightly higher if bonds are breaking, but likely still minimal
- E_thermal: Highest — energy is going into latent heat of vaporization

✔ Answer Summary for Q1:
- From A to B: System gains thermal energy → KE increases.
- From B to C: More thermal energy added → KE increases further; boiling means energy goes into breaking intermolecular bonds (latent heat), so E_thermal continues rising while temperature may plateau.

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## 🔹 Question 2: A can of soda cools down on a table.

This is the opposite of Q1 — energy is leaving the system (soda) to the surroundings (table/air).

States:
- A: Hot soda just taken out of fridge? Wait — actually, if it’s cooling down, it must have been warm initially. Probably meant: soda was warm, now cooling.

Assume:
- A: Soda is warm → high KE, high E_thermal
- B: Cooling → KE and E_thermal decrease
- C: Room temp → KE and E_thermal lowest

PE remains approximately constant (no chemical change).

Bar graphs:

- A: High KE, High E_thermal
- B: Medium KE, Medium E_thermal
- C: Low KE, Low E_thermal

✔ Answer Summary for Q2:
- From A to B: Thermal energy transfers out → KE and E_thermal decrease.
- From B to C: Continues cooling → KE and E_thermal keep decreasing until equilibrium.

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## 🔹 Question 3: A tray of water (30°C) is placed in the freezer and turns into ice cubes (–5°C).

This is a phase change + temperature change scenario.

States:
- A: Liquid water at 30°C → high KE, high E_thermal
- B: Water at 0°C (just before freezing) → KE lower than A, E_thermal lower
- C: Ice at –5°C → KE even lower, E_thermal lowest

Important: During freezing (at 0°C), temperature doesn’t change, but energy is released (latent heat of fusion). So between B and C, if B is liquid at 0°C and C is solid at –5°C, then:

- From A to B: Temperature drops → KE and E_thermal decrease.
- From B to C: Phase change (liquid → solid) → energy leaves system → E_thermal drops significantly even though temp stays 0°C briefly, then temp drops to –5°C → KE decreases further.

✔ Answer Summary for Q3:
- From A to B: Cooling → KE ↓, E_thermal ↓
- From B to C: Freezing + further cooling → KE ↓↓, E_thermal ↓↓ (big drop during phase change)

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## 🔹 Question 4: Where does the energy that leaves the system in Q2 go? How does this energy transfer affect the environment?

This is about conservation of energy and heat transfer.

> “Where does the energy that leaves the system in Q2 go? How does this energy transfer affect the environment?”

Answer:

- The energy that leaves the soda (system) is transferred to the surroundings — primarily the table and air around it.
- This causes the temperature of the surroundings to increase slightly (though usually imperceptibly because the surroundings have much larger heat capacity).
- The energy transfer occurs via conduction (to the table) and convection/radiation (to the air).
- Overall, total energy is conserved — energy lost by soda = energy gained by surroundings.

✔ Final Answer for Q4:
> The energy leaves the soda system and enters the surrounding environment (table and air), causing a slight increase in their thermal energy. This is an example of heat transfer via conduction and convection, and it demonstrates conservation of energy — no energy is lost, only redistributed.

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## 🧠 Bonus Tip: Pie Charts

In the worksheet, there are also pie charts. These likely show the proportion of total energy in the system that is KE, PE, or E_thermal.

For example:
- In Q1 (heating): As time progresses, the slice for E_thermal grows larger.
- In Q2 (cooling): Slice for E_thermal shrinks.
- In Q3 (freezing): At point B (0°C liquid), most energy is still thermal; at C (ice), less thermal energy, but same PE (unless you consider bond energy — which is usually included in PE).

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## ✔ Final Answers Summarized:

Q1 (Cookies boiling):

- Energy flows IN → KE ↑, E_thermal ↑
- Arrangement changes: molecules gain motion → phase change begins

Q2 (Soda cooling):

- Energy flows OUT → KE ↓, E_thermal ↓
- Arrangement changes: molecules slow down → reaches room temp

Q3 (Water freezing):

- Energy flows OUT → KE ↓, E_thermal ↓ sharply during phase change
- Arrangement changes: liquid → solid structure, less molecular motion

Q4 (Energy destination):

- Energy goes to surroundings (table/air)
- Surroundings gain thermal energy → slight temp rise
- Demonstrates conservation of energy

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If you’d like me to help you draw the actual bar graphs or pie charts based on this explanation, let me know! You can describe what you see in the image (e.g., heights of bars, labels), and I’ll guide you on how to fill them in correctly.

Let me know if you want to tackle any specific part in more detail!