Heating Metal Practice

Thinking About Heating And Cooling Metal

In this lesson, you’ll see how heat is transferred from something that is warmer to something that is cooler through a process called 𝐜𝐨𝐧𝐝𝐮𝐜𝐭𝐢𝐨𝐧. We’ll see how it works all the way down at the molecular level. 

Multiple Choice

When the room temperature washers were placed in hot water, what did you notice about the temperature 𝐨𝐟 𝐭𝐡𝐞 𝐰𝐚𝐭𝐞𝐫?

• the temperature of the water increased

• the temperature of the water decreased

• the temperature of the water stayed the same

Multiple Choice

What was the final temperature 𝐨𝐟 𝐭𝐡𝐞 𝐰𝐚𝐭𝐞𝐫 in the cup? Re-watch the video if you do not recall the exact number.

• 31⁰ C

• 41⁰ C

• 51⁰ C

• 61⁰ C

Multiple Choice

Do you think that the temperature 𝐨𝐟 𝐭𝐡𝐞 𝐰𝐚𝐬𝐡𝐞𝐫𝐬 increased, decreased, or stayed the same after they were placed in the hot water?

• The temperature of the washers increased

• The temperature of the washers decreased

• The temperature of the washers stayed the same

The temperature of the washers increased when placed in the hot water, and the temperature of the hot water decreased. 

The final temperature of the water in the cup was 41°C.

Multiple Choice

When the hot washers were placed in the room-temperature water, what did you notice about the temperature 𝐨𝐟 𝐭𝐡𝐞 𝐰𝐚𝐭𝐞𝐫?

• The temperature of the water increased

• The temperature of the water stayed the same

• The temperature of the water decreased

Do you think the temperature 𝐨𝐟 𝐭𝐡𝐞 𝐰𝐚𝐬𝐡𝐞𝐫𝐬 increased, decreased, or stayed the same after they were placed in the room-temperature water? Why?

When the hot washers were placed in room-temperature water, the temperature of the water increased and the temperature of the washers decreased.

The hot washers cooled down as they transferred some of their energy to the water, and the water heated up. 

Conduction

When fast-moving atoms or molecules hit slower-moving atoms or molecules and increase their speed, energy is transferred. The energy that is transferred is called 𝐡𝐞𝐚𝐭. This energy transfer process is called 𝐜𝐨𝐧𝐝𝐮𝐜𝐭𝐢𝐨𝐧.

Multiple Choice

You saw an animation of a metal spoon placed in hot soup. After the spoon was placed in the hot soup, the motion of the atoms in the metal spoon:

• increased

• decreased

• stayed the same

Multiple Choice

You saw an animation of a metal spoon placed in hot soup. After the spoon was placed in the hot soup, the motion of the molecules in the soup:

• increased

• decreased

• stayed the same

Soup Molecules

The molecules in the hot soup are moving faster than the atoms in the spoon. The soup molecules strike the atoms of the spoon and transfer some of their energy to these atoms. This is how the energy from the soup is transferred to the spoon. This increases the motion of the atoms in the spoon. Since the motion of the atoms in the spoon increases, the temperature of the spoon increases.

Moving Molecules

It is not easy to notice, but when the fast-moving soup molecules hit the spoon and speed up the atoms in the spoon, the soup molecules slow down a little. So when energy is transferred from the soup to the spoon, the spoon gets warmer and the soup gets cooler.

Conduction

• When fast-moving atoms or molecules hit slower-moving atoms or molecules and increase their speed, energy is transferred.

• The energy that is transferred is called 𝐡𝐞𝐚𝐭.

• This energy transfer process is called 𝐜𝐨𝐧𝐝𝐮𝐜𝐭𝐢𝐨𝐧.

You saw an animation of a hot metal spoon placed in room-temperature water.

After the spoon was placed in the water, how did the speed of the atoms in the metal spoon change and how the speed of the molecules of the water change?

In the animation, you saw a finger touch metal and cardboard which were both at room-temperature. The metal felt cold, but the cardboard didn’t feel as cold.

If metal is better at conducting heat than cardboard, why did the metal feel colder than the cardboard when they are the same temperature?

The Answer

The molecules in your finger are moving faster than the molecules in the room-temperature metal. Therefore the energy from your finger is transferred to the metal. Because metal is a good conductor, the energy is transferred away from the surface through the metal. The molecules in your skin slow down as your finger continues to lose energy to the metal, so your finger feels cooler.

The molecules in your finger are also moving faster than the molecules in the room-temperature cardboard. Energy is transferred from your finger to the surface of the cardboard. But because cardboard is a poor conductor, the energy is not easily transferred away from the surface through the cardboard. The molecules in your skin move at about the same speed. Because your finger does not lose much energy to the cardboard, your finger stays warm.

At any temperature, the atoms or molecules of a substance are moving at a variety of speeds. Some molecules are moving faster than others, some slower, but most are in-between.

Kinetic Energy

Anything that has mass and is moving, no matter how big or small, has a certain amount of energy called kinetic energy. The temperature of a substance gives you information about the kinetic energy of its molecules. The faster the molecules of a substance move, the higher the kinetic energy, and the higher the temperature. The slower the molecules move, the lower the kinetic energy, and the lower the temperature. Since there are so many molecules of a substance, temperature is actually a measure of the 𝐚𝐯𝐞𝐫𝐚𝐠𝐞 𝐤𝐢𝐧𝐞𝐭𝐢𝐜 𝐞𝐧𝐞𝐫𝐠𝐲 of the molecules of a substance.

Multiple Choice

In the animation, what did the color of a particles tell you?

• The size of the particle

• The type of particle

• The speed of the particle

• The mass of the particle

Multiple Choice

When the substance was heated by adding energy, what happened to the average speed of the molecules?

• increased

• decreased

• stayed the same

Multiple Choice

Temperature is related to the average _________________________ of the molecules of a substance.

• size

• shape

• potential energy

• kinetic energy

Copy Into Your Science Notebook

• Adding energy (heating) atoms and molecules increases their motion, resulting in an increase in temperature.

• Removing energy (cooling) atoms and molecules decreases their motion, resulting in a decrease in temperature.

• Energy can be added or removed from a substance through a process called conduction.

• In conduction, faster-moving molecules contact slower-moving molecules and transfer energy to them.

Copy Into Your Science Notebook

• During conduction the slower-moving molecules speed up and the faster-moving molecules slow down.

• Temperature is a measure of the average kinetic energy of the atoms or molecules of a substance.

• Heat is the energy transferred from a substance at a higher temperature to a substance at a lower temperature.

• Some materials are better conductors of heat than others.

Multiple Choice

Did you copy the big ideas into your science notebook?

• Yes

• No

Poll

How do you feel about what you have learned in this lesson?

• 😊 Great! I am confident that I understand the material.

• 🙂 Good, but I still have a question. I will ask the teacher about it by email or in class.

• 😐 OK, but I need more practice. I will read through the lesson and re-watch some of the videos.

• 🤨 I need help. I will review the lesson and make a list of topics that are confusing to me. I will reach out to the teacher for help.