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Hello everyone, how are you?
I hope you're doing really, really well today.
My name is Miss Afsal and I'll be your teacher for this lesson.
I'm feeling really quite pleased about that because we've got an interesting topic ahead.
We're looking at heating and cooling.
I wonder if that's something you've thought much about and wonder if it's something you know much about.
Don't worry, whatever is the case we are gonna be diving into the subject today.
Our lesson is called heating and cooling and it comes from the unit of work fuels and energetics.
So, if you are ready to get right into this topic of heating and cooling, if you have some energy, focus, and enthusiasm, we'll begin our lesson now.
The outcome for today's lesson is, I can explain why some changes of state are exothermic and some are endothermic.
I hope that sounds interesting to you.
We have some key words in our lesson.
I'd like us to go through them one at a time.
Say them out loud.
My turn, your turn.
Exothermic.
Endothermic.
Good to hear those key words and now I'd like you to turn to someone and share with them, have you heard of any of these keywords before?
Do you have any idea what they mean?
Pause here and share with someone.
Thanks for sharing.
Let's find out what these keywords mean.
Exothermic is when a substance transfers energy out to the surroundings by heating, e.
g.
condensing and freezing.
Endothermic is when a substance transfers energy in from the surroundings, e.
g.
melting, boiling, and evaporating.
So, these are our keywords, exothermic and endothermic.
Let's look out and listen out for them.
Let's think carefully about them.
They'll be coming up in our lesson today.
Today's lesson is called heating and cooling and it has three elements.
Heating and cooling, endothermic and exothermic, and energy transfers.
Let's begin by exploring heating and cooling.
When a substance is heated the temperature of that substance increases.
The water in a kettle has been heated, it is now at a higher temperature.
25 degrees and now it's at 100 degrees C.
When a substance cools, the temperature of that substance decreases.
The fizzy drink has cooled in a fridge.
It is now at a lower temperature.
It's gone from 25 degrees C to 4 degrees C.
Let's have a check for understanding.
Which of the images have objects that have been heated?
A, a cooked pizza?
B, water in the snowball?
C, a hot water bottle?
Pause here while you select which of these images have objects that have been heated.
Well done if you selected A, cooked pizza and C, a hot water bottle.
Both of these objects have been heated.
When a substance is heated energy is transferred from the surroundings to the substance.
Like so.
There's energy from the surroundings being transferred into the substance as it is heated and when a substance cools energy is transferred from the substance to the surroundings.
The water is being heated.
The energy is being transferred from the hot flame, surroundings of the water to the water.
So, there we can see that energy being transferred from the flame to the water.
The cup of tea is cooling down.
The energy is being transferred from the hot cup of tea to the cooler surrounding air.
Here we can see the energy moving out from the hot cup of tea.
Let's have a check for understanding.
When a substance is heated, finish the sentence by choosing from one of these three options.
A, energy is transferred from the surroundings to the substance.
B, energy is transferred from an object to the surroundings.
Or C, there is no transfer of energy.
So, pause here while you decide how to complete this sentence.
Well done if you selected answer A.
Energy is transferred from the surroundings to the substance.
Let's read the sentence in full.
When a substance is heated energy is transferred from the surroundings to the substance.
Well done if you chose this answer.
Let's have another check for understanding.
Which student has got the best description of cooling?
Izzy, it's a bit like heating.
Energy moves from the surroundings to whatever is being cooled.
Or Sam, it's like the opposite of heating.
The energy moves from the hot tea to the air when a cup of tea is cooling.
And here's Laura.
Energy always stays in one place, it cannot move.
Pause here while you decide which student has got the best description of cooling.
Laura, Izzy, or Sam.
Well done if you selected Sam.
Indeed this is a great description of cooling.
It's like the opposite of heating.
The energy moves from the hot tea to the air when a cup of tea is cooling.
And now it's time for your first task.
I would like you to draw two lines from heating and two lines from cooling to match up the descriptions.
So, there we have our words heating and cooling and their descriptions.
Let's read through them.
Temperature of substance increases.
Temperature of substance decreases.
Energy transferred to substance from surroundings.
Energy transferred from substance to surroundings.
So, pause here while you draw two lines from heating and two lines from cooling to match up the descriptions.
Pause here while you have a go at this and I'll see you when you're finished.
It's good to be back with you.
How did you get on with that task?
Of drawing two lines from heating and two lines from cooling to match up the descriptions?
Heating is when the temperature of a substance increases and energy is transferred to substance from surroundings.
And cooling is when the temperature of substance decreases and energy is transferred from the substance to the surroundings.
Well done if you matched up heating and cooling with these descriptions.
Well done for having a go at this task.
And now we're onto our next learning cycle endothermic and exothermic.
Heating transfers energy from the surroundings into a substance.
The substance heats up, it may melt, evaporate, or boil.
This is an endothermic process.
There's our keyword.
Endothermic is made up of endo, which means into, and thermic, which means caused by heat.
So, in this image we can see the energy from the surroundings is causing the substance, the ice to melt.
The heat, thermal energy is transferred into the substance.
And there we can see again our parts of the keyword, the heat, thermic, and it's transferred into the substance, endo, means into.
Cooling transfers energy out of the substance into the surroundings.
The substance cools down, it may condense or freeze.
This is an exothermic process.
There's our other keyword.
Exothermic consists of exo, which means out of and thermic, remember that one?
Caused by heat.
So, here we can see in this image from the hot tea the energy is being transferred to the surroundings.
The heat, thermal energy is transferred out of the substance.
And again, we can relate that back to our keyword, heat, thermic, and out of is exo.
Exothermic.
And here's a table that we can complete for endothermic and exothermic.
So, when something is endothermic the energy is being transferred from the surroundings and the energy is transferred to the substance.
For example, when we heat up some water.
The temperature change of the object increases and the temperature change of the surroundings decreases.
And let's take a look at exothermic.
Energy is transferred from the substance.
The energy is transferred to the surroundings.
For example, when a hot cup of tea cools down.
The temperature change of the object decreases whilst the temperature change of the surroundings increases.
Let's have a check for understanding.
Energy is transferred from a hot meal.
This process is called, choose from the selection.
A, exothermic because energy is transferred from the food to the surrounding air.
B, exothermic because energy is transferred from the surrounding air to the food.
Endothermic because energy is transferred from the food to the surrounding air.
Or endothermic because energy is transferred from the surrounding air to the food.
Pause here while you decide what the process is called when energy is transferred from a hot meal.
Well done if you selected answer A, indeed.
This process is called exothermic because energy is transferred from the food, from the hot meal to the surrounding air.
And now it's time for your next task.
I would like you to complete the diagram to show endothermic and exothermic processes.
So, for each beaker of water, I'd like you to add arrows to show where the energy transfers take place and add labels showing, A cooling, B, heating, C, endothermic, D exothermic.
And remember, the surroundings are 20 degrees C, that's important to note and the temperature of the water in one beaker is 3 degrees C and the other it's 85 degrees C.
So, pause here while you have a go at this task showing the energy transfers with arrows and then adding the labels.
Cooling, heating, endothermic, and exothermic.
I'll see you when you're finished.
It's good to be back with you.
How did you get on with that task?
Let's take a look.
Here we can see that the energy has been transferred from the surroundings.
We can see those arrows.
And here we can see that energy has been transferred to the surroundings.
And the arrows are going outwards.
On the left we can see that heating is taking place.
On the right cooling is taking place.
And we can add in the words on the left, endothermic and on the right, exothermic.
Well done if you completed your task in this way.
And now we're onto our final learning cycle, energy transfers.
A substance in a solid state is placed in a beaker with a thermometer.
The beaker is heated and the temperature measured every 10 seconds.
A graph of the results can be plotted.
It's called a heating curve.
With temperature on the one axis and time along the other.
So, we can see that the temperature of the substance increases as the energy is transferred to the substance.
The particles remain in a fixed position.
The vibrations increase.
Next, the substance starts to melt.
The energy is used to overcome the forces of attraction.
The temperature does not increase and we can label this melting and there we can see the melting point.
Now, our substance is in a liquid state.
Once the substance is melted the temperature of the liquid will start to increase again.
As the energy is transferred to the substance the particles start to move more.
When the substance starts to boil the energy is used to overcome the forces of attraction until all the substance is in a gas state.
The temperature does not increase.
And here we can see the boiling point.
Once the substance has boiled and is in a gas state the temperature of the gas will start to increase again.
So, here's the final version of our heating curve.
Let's have a check for understanding.
What part of the graph shows the substance is melting?
Is it A, B, C, or D?
Pause here while you decide.
Well done if you selected B.
This part of the graph shows the substance is melting.
Let's have another check for understanding.
What part of the graph is the substance in the gas state?
A, B, C, or D?
Pause here while you decide.
Well done if you selected D.
This part of the graph is the substance in the gas state.
Let's have another check for understanding.
What part of the graph shows the substance is boiling?
Is it A, B, C, or D?
Pause here while you decide.
Well done if you selected C.
This part of the graph shows the substance is boiling.
Let's have another check for understanding.
What parts of the graph shows the forces of attraction between the particles being overcome?
Is it A, B only?
B, B and C?
C, A only?
Or D, A and D?
Pause here while you decide.
Well done if you selected answer B.
Indeed it is sections B and C on the graph show the forces of attraction between the particles being overcome.
This graph shows us the substance in it's solid state, liquid state, and gas state.
Shows us where it is melting and boiling and here is the melting point and the boiling point.
Melting point was 45 degrees C and boiling point was 75 degrees C.
Scientists can carry out a similar experiment starting with the substance in a gas state but this time cooling the substance.
They can measure the temperature at regular time intervals and this is called a cooling curve.
So, we have the gas state, the liquid state, and then the solid state.
We have the processes of condensing and freezing and the condensing point and the freezing point.
Let's have a check for understanding.
True or false?
This graph represents cooling data.
Pause here while you decide, is this statement true or false?
Well done if you selected true and now I'd like you to justify your answer by choosing from one of these two statements.
A, as the time increases the temperature increases.
Or B, as the time increases the temperature decreases.
Pause here while you decide which of these statements justifies your earlier answer.
Well done if you selected statement B, indeed.
As the time increases the temperature decreases.
And this justifies your earlier answer.
Let's have another check for understanding.
Which part of the graph shows the gas condensing?
Is it A, B, C, or D?
Pause here while you decide.
Well done if you selected B.
Let's have another check for understanding.
Which part or parts of the graph show the temperature staying the same?
Option A, A and D?
Option B, B and C?
Option C, A only?
Or Option D, B only?
Pause here while you decide.
Well done if you selected option B.
Indeed it is B and C which show the temperature staying the same.
Let's have another check for understanding.
The freezing point of candle wax is 65 degrees C.
Which graph shows the correct information?
A, B, or C?
Well done if you selected graph B.
And now, it's time for your final task.
One, I would like you to add missing labels to the cooling curve.
You will not need to use all of them and two, add labels to the axis showing the condensing point at 225 degrees C and the freezing point at 120 degrees C.
So, pause here while you have a go at this task.
Adding the missing labels and adding labels to the axis and showing the condensing point and the freezing point.
I'll see you when you finished.
It's good to be back with you.
How did you get on with that task?
Let's have a look.
Here we have the axis correctly labeled with temperature in degrees C.
We have the gas state and the solid state, condensing, and here's our freezing point of 120 degrees C and our condensing point of 225 degrees C.
Next, I would like you to choose the correct labels to add to the curve.
You will not need to include all the labels.
Here are your options, A, title, heating curve or cooling curve.
B, axis, time, temperature.
C, gas state, liquid state, solid state.
D, boiling, condensing, freezing, melting.
E, boiling point, condensing point, freezing point, melting point.
And F, the substance melts at 50 degrees C and boils at 110 degrees C.
Add these labels to the axis of your curve.
So, pause here while you have a go at correctly labeling your curve.
And remember you will not need to include all the labels.
I'll see you when you're finished.
It's good to be back with you.
How did you get on with that task of completing the heating curve?
Here's axis, temperature and time.
Solid state, liquid state, gas state.
Here we can see where the substance was melting and boiling.
Here's our melting point and our boiling point of 50 degrees C melting point and 110 degrees C for the boiling point.
And finally, I would like you to complete the gaps with increases, decreases, stays the same, attraction, repulsion.
You may use the words more than once.
Initially, the temperature of the substance.
.
.
until it starts to melt.
Then energy is needed to overcome the forces of.
.
.
this means that the temperature of the substance.
.
.
Once all the substance is in the liquid state, the temperature of the substance.
.
.
Until the substance starts to boil.
Energy is then needed to overcome the forces of.
.
.
Between particles so the temperature.
.
.
Once all the substance is in the gas state the temperature.
.
.
So, pause here while you complete the gaps in these sentences and remember you may use the words more than once.
So, how did you get on with that task of completing the gaps in the sentences?
Let's read through them.
Initially the temperature of the substance increases until it starts to melt.
Then energy is needed to overcome the forces of attraction.
This means that the temperature of the substance stays the same.
Once all of the substance is in the liquid state the temperature of the substance increases until the substance starts to boil.
Energy is then needed to overcome the forces of attraction between particles so the temperature stays the same.
Once all the substance is in the gas state the temperature increases.
Well done if you completed the task in this way.
In our lesson heating and cooling, we've covered the following.
Heating transfers energy into a substance and can cause it to melt, evaporate, or boil.
Melting, evaporation, and boiling are endothermic.
As it cools, a substance transfers energy into the surroundings by heating and it may condense or freeze.
Condensing and freezing are exothermic.
Well done everyone for joining in with this lesson.
It was so interesting to explore heating and cooling.
Learn about these great words, endothermic and exothermic.
So, next time you have a hot or a cold drink you can confidently know what processes are taking place as your drink heats or cools.
I really enjoyed teaching you.
I hope you enjoyed this lesson and learned a lot and I look forward to seeing you at another lesson soon.
Until then, stay curious.
