This quiz will assess you on knowledge learned in today's lesson, as well as what you have learned in earlier lessons.

What is the law of conservation of mass?

Reaction rate graphs: The less steep the curve...

What is the total mass of products if the total mass of reactants is 125g?

What must all rate practicals measure?

Why do we have the highest frequency of successful collisions at the start of the reaction?

Review 2

﻿Hello and welcome to your final lesson in Energyetics. It's Miss Charlton here. This lesson, we're going to look into planning and investigation in endo and exothermic reactions. What you're going to need today is a pen and some paper. Please pause the video to go and get them now and resume when you're ready to begin. Now for the final time in the topic, let's start. In our final lesson, we will be identifying variables from a hypotheses. Writing a good method and then recapping how to record and process data. To start us off, we'll do some revision of exo and endothermic reactions. In endothermic reactions, the energy taken and in during the bond breaking part of chemical reactions is greater than the energy released when forming new bonds. Bond breaking requires energy which is taken in first from the thermal store of the reaction mixture then from the surroundings if more is required. This generally causes a temperature decrease. In exothermic reactions the energy released when new bonds are made is greater than the energy taken in during bond breaking. This energy is released into the thermal store of the surroundings, which can lead to a temperature increase. To revisit another slide from our previous lesson here we calculated the temperature change and decided if the reactions were exo or endothermic. A positive temperature change proved an exothermic reaction probably took place. Whilst a negative temperature change indicated an endothermic reaction likely took place. We're now going to move on to identifying variables. I'm not to struggle remembering which ones are which but variables are crucial in any experiment or investigation. So try to memorise them. The independent variable is what we will change. The dependent is what we will measure because of that change. And the control variables are what must stay the same so they don't affect the results. We are going to investigate two very similar practicals. The reaction between water and ammonium nitrate and the reaction between sodium hydroxide and hydrochloric acid. The equipment we would need for these practicals would be, a stop clock to check our timings and a thermometer to measure the temperature change. Identifying variables is difficult, but I'm here to assist you if you do struggle. Let me give you some tips before we start. You will find the independent and dependent variable in the hypothesis itself. Look for comparison words, such as effects, changes, lows, increases, faster and slower. On either side of these words will be the independent and dependent variables. Your control variables will always be slightly harder to work out 'cause they will not be found in the hypothesis. You must think about what could affect the practical if it were not controlled. Factors such as temperature, concentration, volumes and masses only controlling if they're not going to be purposefully changed as the independent variable. I'll do the first one for you. My hypothesis is, the greater the mass of ammonium nitrate dissolved in water, the greater the temperature decrease. What I start by doing is identifying factors in the hypothesis. In this one, I have a mass of ammonium nitrate and temperature. I know both of these as separate factors as they have the word greater in front of them, but are most identified which one I can purposefully change easily and which will be affected by the other changing. In this experiment, I can easily change the mass of ammonium nitrate so this would be my independent variable. And this could easily change the temperature. So my dependent variable would be temperature change. And I'll measure that with a thermometer. Now to think outside of the box for my control variables. For any practical which involves measuring temperature change, we must always keep the container and the lead if it has one the same. This maintains the energy transfers occurring when repeating the experiment. Another factor which could affect the experiment would be the volume of water the ammonium nitrate is dissolved in. If this was not controlled, my data would be unreliable as more than one factor is changing. Try and give this one a go yourself. Take your time to read through the hypotheses carefully. Think about which can be changed easily and which will be affected by the change. Remember your units, pause the lesson now to attempt the task and resume when you're finished. Well done if you managed to get any of these and their units. The independent variable is the volume of sodium hydroxide in centimetres cubed. The dependent variable is the temperature change in degrees Celsius. Under control could be any of these. The material of the container and lead, the volume of hydrochloric acid and the concentration of the acid as well. Now I pass the variables, let's move on to writing a method for the practical. Here is a poorly written method. Pause the lesson now to read through it and play it when you're done. I'll then explain why it's not great and how it could be improved. I always start by making sure I use clear numbered steps to order my method. This method hasn't done that so that would be my first improvement. If I were to attempt this practical using these instructions I would have no idea how much reactants I would use. So to improve this, I would add in given volumes and masses. Adding in named equipment is very important as using incorrect equipment to measure can lead to inaccurate or misleading data being produced. There must also be information about how to record the dependent variable which we will look into after we wrote our method. And finally, if we need to repeat steps to change independent variable, we must say how we change it and be specific when different volumes or masses are used, but also mention what will be kept the same. Here is my advice at bullet point . Take a minute to read through them and make sure you're doing each one whenever writing of method. All three types of variables should be mentioned. Pause the video to read through the bullet points and play when you're finished. My improvement method achieves each one of those previous bullet points. It has a number sequence, named equipment, masses and volumes of all chemicals and all my variables are present. Pause the lesson to read through my improved method and play when you're done. Your turn now. Write a method for the other practical. Use the variables you identified before. Pause the video now to complete the task and resume when you're finished. Hopefully you managed to get a method written down. This is mine. Pause the lesson now to compare your method to mine and see if you can improve it. If not, well done. Moving onto the final bit of the lesson now. Recording and processing data. We have gone through tables earlier on in this topic. However, its always good scientific practise to advise how to correctly record data in a table. You must have the independent variable in the left column. Full headings and units, unless told otherwise, include repeating columns and means. Results written to the same decimal places as the instrument, and always check for anomalies and exclude them from the mean. Which table titles would be best and why? A, B, C or D. It will be answer D, because the independent variable is in the first column with units and the dependent variable is in the second column with the units as well. I've also used the word volume not amount. I design the table for the first practical to assist you in drawing yours. I followed my own advice for drawing my table. The independent variable is in the first column with units and my masses going up in equal intervals. Then, my dependent comes after. As I'm carrying out repeats to calculate a mean, I've included four columns under my dependent variable which also has a unit. Time for you to design one similar to mine using the hypotheses from before. Complete the task now and resume when you're finished. Here is the table design you should have drawn. It is difficult to draw the repeat test columns in, so if you didn't get it perfect don't worry. With practise you will eventually get there. Before we calculate the mean, we would check for anomalies. And I can see that in the second experiment one gramme is an anomaly, is it doesn't fit the other temperatures. So I'm not going to include that. All the others look fine. So I'm going to go ahead and calculate the mean temperature decrease for the rest. And remember to round my mean to the same number of decimal places as the original readings. In this case is whole numbers. My trend would be, the greater the mass of ammonium nitrate, the greater the temperature decrease. It does tail off at the end so the temperature decrease will eventually stop. Calculate the mean of this data, then describe the trend of the mean data. Remember to talk about the volume of sodium hydroxide added and the temperature increase. Pause the lesson now to complete the task and resume when you're done. Here are the answers. Hopefully you spotted that 15 was an anomaly. Pause the video and check your answers to the main calculation on the trend. Again, it tails off at the end. So would only follow the trail until a certain of sodium hydroxide is added. Congratulations, you finished the energetics topic. The summary points to this last lesson are, the independent and dependent variables can be identified from a hypothesis. A good method should also include named equipment, all variables and specific volumes and masses. The independent variable must be the first in the column to the left in a table. And both variables must include units in the title. Please continue your learning with other topics on our Oak Academy website.

What must a good method include?

What piece of equipment will you need every time you measure the rate of reaction?

Where does the independent variable go in a table?

What do you need to check for once you have written results in a table before calculating the mean?

In endothermic reactions

Investigation

Plan an investigation looking into exothermic vs endothermic reactions

This lesson explains how to plan an investigation looking into exothermic vs endothermic reactions.

Science

Y9 Science

Key Stage 3

Year 9

Miss

Investigation: Exo vs. Endo

Energetics and rates

Chemistry

THEME

UNIT

What is a rate?

Reaction rate graphs

Secondary data

The Effect of concentration

The Effect of surface area

Catalysts

Exothermic and endothermic reactions

Combustion

Complete and incomplete combustion

Thermal decomposition

Review (Part 1)

Mildred Cohn

Review (Part 2)

When the surface area of a solid increase...

Increasing the surface area...

What are the products of complete combustion?

What effect do catalysts have on the rate of a reaction?

What do catalysts do to activation energy?

Why are catalysts crucial in industry?

What are the products of incomplete combustion?

What is the test for carbon dioxide?

What has to happen to the reactant particles before they can react?

How could we measure the rate of reaction if the reaction changes colour?

What is the minimum amount of energy needed to start a reaction called?

Which piece of equipment can be used to measure the volume of gas given off in a reaction?

When there are no reacting particles left...

What is an anomaly?

When is sulphur dioxide produced?

What is the test for oxygen?

What is the temperature change when the start temperature is 75 degrees Celsius and the end temperature is 83 degrees Celsius?

How would I recognise a exothermic reaction?

Which store does exothermic reactions transfer energy from?

By changing a beaker for a Styrofoam cup and lid we

If my reactant has a mass of 5.5g and one of my products has a mass of 2.45g, what is the mass of my other product?

What are the products of the thermal decomposition of magnesium carbonate?

Which answer correctly describes the effect of concentration on the rate of reaction?

Lesson overview:Investigation: Exo vs. Endo

Energetics and rates: