Using Heat

Chemistry Unit 3 Lesson 1: Heat,Temperature, and Phase Changes.

​HEAT VS. TEMPERATURE

​Despiste what we think heat and temperature are not the same.

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​For example if i was to ask you which item on the right is hotter, What would you say?

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​Simply use your prior knowledge of these items to answer.

Poll

Which one is hotter?

• Swimming Pool

• Cup of Coffee

​HEAT VS. TEMPERATURE

​If you answered the coffee cup then in fact you were using temperature for your basis of comparison.

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​The coffee cup most definitely has a higher temperature then the above ground swimming pool.

​HEAT VS. TEMPERATURE

​If you answered the swimming pool then in fact you were using heat for you basis of comparison.

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​This the trickier one to understand.

​HEAT VS. TEMPERATURE

Temperature is defined as the average kinetic energy of all the molecules of a substance.

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​HEAT VS. TEMPERATURE

Temperature is defined as the average kinetic energy of all the molecules of a substance.

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​While heat is defined as the total kinetic energy of all the molecules of a substance.

Multiple Choice

Which one of these would have the highest TOTAL? (HEAT)

• 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1 = __

• 5+5+5 = __

Multiple Choice

Which one of these would have the highest AVERAGE? (TEMPERATURE)

• 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1 = __

• 5+5+5 = __

Open Ended

Which of the following A or B represents the pool? Describe why you think this.

A. 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1 = 25

B. 5+5+5 = 15

​HEAT VS. TEMPERATURE

So one way to understand the difference with these two items is to imagine what would happen if we poured the coffee into the pool.

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​The coffee had a high temperature. Each molecule has a high amount of energy (it's moving really fast). It's just that in comparison to the pool the coffee cup does not have that many molecules.

​HEAT VS. TEMPERATURE

So when the coffee would get poured in; it would not change much about the average kinetic energy of the pool.

​HEAT VS. TEMPERATURE

So when the coffee would get poured in; it would not change much about the average kinetic energy of the pool.

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Meaning the temperature of the pool would more or less stay unaffected.​

​HEAT VS. TEMPERATURE

This is why we could say the pool has more HEAT. The total energy it possesses is so much higher simply because it has so many more molecules.

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​HEAT VS. TEMPERATURE

This is why we could say the pool has more HEAT. The total energy it possesses is so much higher simply because it has so many more molecules.

The importance of how heat and temperature play a role is in how we calculate the way matter behaves when interacting with energy.

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​HEAT VS. TEMPERATURE

Multiple Choice

Which of the following most likely has the highest temperature?

Multiple Choice

Which of the following most likely has the highest heat?

Open Ended

Summarize the difference between heat and temperature in your own words.

​HEAT VS. TEMPERATURE

If it still is hard to understand:

​Try to envision this energy thing like a subatomic game of tug of war.

​HEAT VS. TEMPERATURE

The coffee cup is small but has a high average energy (Temp.). So we imagine it has 4 body builders on its team for tug of war.

​HEAT VS. TEMPERATURE

The pool is large but has a low average energy (Temp.). So we imagine it has 400 kids on its team for tug of war.

​HEAT VS. TEMPERATURE

The average strength of each person is like temperature. Stronger = Hotter.

​HEAT VS. TEMPERATURE

The TOTAL strength of the whole team is like heat.

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​HEAT VS. TEMPERATURE

Also very important is how mass affects how changes in energy are seen as changes in temperature. The more mass an object has, or molecules, the more energy it can take on or lose before it begins to change temperature.

​HEAT VS. TEMPERATURE

This is why your cup of coffee might cool very quickly but Smithville Lake would require several days of temperatures below freezing before every beginning to freeze.

It is also why the pool can be very cold for the first few weeks of summer.

​HEAT VS. TEMPERATURE

We will also find out next class that the type of substance plays an important role on how stuff heats up and cools down.

​Hot and Cold

​Do you sometimes find it hot in a room or space while someone else might say they are cold?

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How can that be? And if it is so confusing how can we define the difference between these two words?​

Open Ended

How would you define hot vs. cold based on what you have learned so far? Try to create what you think is a proper scientific definition.

Multiple Choice

Which felt "colder" to all audience members?

• Hard Drive

• Book

Multiple Choice

Which felt "colder" to all audience members?

• Aluminum Block

• Plastic Block

Multiple Choice

Which actually melted the ice much faster?

• Aluminum Block

• Plastic Block

Open Ended

The lab tables in our connected room work much the same way as the aluminum block. A textbook left in the room at the exact same "Temperature" would feel much warmer to you than the lab table tops. Using what you saw in the video as a guide write out an explanation like you were talking to another student how two things can "feel" a different temperature when in fact they are the same.

​Hot and Cold

​So what we should take from this video is the idea that hot and cold are relative terms.

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​We use these terms in how we interact with the objects we touch.

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​Heat flows between objects from high to low based on temperature.

​Hot and Cold

If we lose heat to an object, to us that feels cold.

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​If we gain heat from an object, to us that feel hot.

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​Exothermic and Endothermic

We see a similar pattern with chemical reactions in chemistry as well.

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​Some reactions tend to give off excess energy in the form of heat. Such as if I were to burn a piece of paper.

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​These reactions are classified as Exothermic reactions.

​Exothermic and Endothermic

​Some reactions tend to absorb excess energy in the form of heat. Such as if an ice cube were to melt.

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​These reactions are classified as Endothermic reactions.

Multiple Choice

What kind of reaction do you think is pictured here?

• Exothermic

• Endothermic

​Exothermic and Endothermic

​So exothermic reactions tend to give off heat while endothermic reactions tend to absorb heat.

​Heat flows

​So heat is an energy that flows from one object to another.

​The Law of Conservation of Energy says that energy is not created or destroyed by merely transferred or transformed.

​We learned this is Physical Science and it holds true with Heat as well.

​Heat flows

There are 3 main ways heat can be transferred.

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​The easiest to understand is conduction.

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​Heat transferred through conduction is where two items are touching.

Open Ended

Describe a time where heat is conducted. Be specific.

​Heat flows

There are 3 main ways heat can be transferred.

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​Convection is another one you might have heard of.

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​Convection is the transfer of heat from one place to another due to the movement of a fluid.

​Heat flows

There are 3 main ways heat can be transferred.

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​The final is Radiation.

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​Radiation is the process by which energy, in the form of electromagnetic radiation, is emitted by a heated surface in all directions.

​Heat flows

​Radiation sounds very similar to convection. The difference is that matter is not needed to carry the energy from one place to another.

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So a common form a radiation heating we see is how the sun's heat travels here to earth through the vacuum of space. ​

​Heat vs Temperature

​Like with all other properties of matter we've looked at in chemistry, we need to measure the heat and temperature of a substance.

When we measure something we have a unit focused on this measurement. ​

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​Heat vs Temperature

​​We are used to measuring temperature.

​We commonly do so for weather purposes in fahrenheit.

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We also hopefully know that celsius is the common metric unit for temperature.

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​Heat vs Temperature

​In this unit we will also need to be able to convert temperature into units of Kelvin.

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​Kelvin is an adjusted temperature scale so that temperatures can never go negative.

​Heat vs Temperature

To convert Fahrenheit to Celsius.

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​F -32 x 5/9 = C

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​You will be given the formula on tests to use. We won't be expected to memorize it. But please practice it on homework rather than using google for conversions.

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Doing so will help you prepare.​

​Heat vs Temperature

To convert Celsius to Fahrenheit

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​C x 9/5 + 32 = C

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​Notice how the formula basically flips including the fraction.

​Heat vs Temperature

To convert Celsius to Kelvin

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​C +273 = K

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​so

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​K -273 = C

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​You cannot go straight from F to K. You must go to C 1st.

Multiple Choice

Convert 89.00 ^oF to ^oC

• 31.67^oC

• 106.8^oC

• 71.22^oC

• 102.6^oC

Multiple Choice

Convert 400.0 K to ^oF

• 260.6^oF

• 127.0^oF

• 196.6^oF

• 102.6^oF

​Phases of Matter

One of the final things we want to discuss with heat, temperature, and matter is how energy affects the state or phase matter is in.

​Phases of Matter

There are 3 main phases of matter.

These phases of matter are defined by their shape and volume.

Matter can be found in each of the phases based on the movement of its molecules or the temperature it is at. ​

​Phases of Matter

As we've already discussed higher temperatures are a measure of higher average molecular movement. As molecules move more they have to spread out to do so. This affects the state the matter takes on.

​Phases of Matter

Solid is defined as a phase of matter with a set shape and a set volume.

So with very little movement this state is usually where matter has the least amount of heat.

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​Phases of Matter

Liquid is defined as the state of matter with NO set shape but a set volume.

Movement is far more than that of a solid therefore we can assume that the matter needs more energy to enter this state.

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​Phases of Matter

Gas is defined as the state of matter with NO set shape and NO set volume.

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​Gases will expand to fill their container.

So with tons movement this state is usually where matter has the highest amount of heat.

​Kinetic Theory of Matter

​The Kinetic Theory of Matter is simply the idea that all objects are in motion all the time.

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​This theory helps us to explain and better understand the phases of matter but also the phase changes these forms of matter can undergo.

​An experiment we use to demonstrate the kinetic theory of matter is the diffusion rate in liquids with food coloring.

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​Here we can see their must be greater molecular movement in the water with a higher temperature causing the food coloring to diffuse faster.

​Phase Changes

​There are 6 main phase changes -

​Vaporization - Liquid to Gas

​Condensation - Gas to Liquid

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​Melting - Solid to Liquid

​Freezing - Liquid to Solid

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​Deposition - Gas to Solid

​Sublimation - Solid to Gas

Multiple Choice

Which Law/Theory states that all atoms and molecules are constantly in motion.

• Law of Definite Proportions

• Law of Multiple Proportions

• Kinetic Theory of Matter

• Potential Theory of Matter

Multiple Choice

Which phase of matter has a definite shape but NO definite volume?

• Solid

• Liquid

• Gas

• This matter doesn't exist

Multiple Choice

Which phase change occurs when a liquid becomes a gas?

• Decomposition

• Condensation

• Sublimation

• Vaporization

​Lesson Summary

​So in this unit we basically had 5 objectives

1. I can differentiate between heat and temperature.

2. I can differentiate between endothermic and exothermic.​

3. I can describe the 3 ways in which heat ​flows.

4. I can convert between ^oC, ^oF, and K​.

5. I can describe the phase of matter and identify the changes between each.