Checkpoint Task

Topic C3: Chemical reactions

Instructions and answers for teachers

These instructions cover the student activity section which can be found on page 6. This Checkpoint Task should be used in conjunction with the KS3–4GCSE (9-1) Gateway Science Chemistry A Transition Guide: Chemical reactions, which supports OCR GCSE (9-1) Gateway Science Chemistry A.

When distributing the activity section to the learners either as a printed copy or as a Word file you will need to remove the teacher instructions section.

Introduction

This task is designed to provide challenge for learners at different levels; the questions are designed to be quick to answer so that the task can be completed quickly in a lesson but still give valuable information about a variety of skills.

Answer the following questions:

Use the Periodic Table to help you on some of the questions.

Learners should be provided with a copy of the Periodic Table and possibly a list of common ions (one such list is on the ‘Ionic compounds’ activity).

  1. What is the name for CO?

Put a circle around the correct answer.

carbon oxide carbon monoxide carbon dioxide

This question shows whether learners can identify the elements in a compound but also whether they understand the naming prefix mono/di.

  1. Look at the two equations below.

(a)Complete the word and symbol equations.

lithium + 

Li + O2

(b)In this reaction, what is the state of lithium?

Part (a) tests if learners can identify elements easily AND determine what chemicals would be formed. It is also testing if they can work out ionic compounds using their position on the Periodic Table. A difficult task.

Part (b)simply tests their understanding of the word ‘state’.

  1. Which of the following is Avogadro’s number?

Put a circle around the correct answer.

6 x103 6.02x1023 6x10-20

Recalling numbers in standard form can be difficult. The ‘distractors’ are designed to make learners think.

  1. How many moles are there in 12.15g of magnesium?

= 12.15 (mass) / 24.3 (relative mass)

Number of moles =

Mole calculations are easy when you know how so this question will show who knows about this and who does not.

  1. If 48g of magnesium reacts with 32g of oxygen, what mass of magnesium oxideis produced?

g

This question is testing learners’ understanding of the conservation of mass.

  1. Complete the energy level diagram for an endothermic reaction.

The reactants are placed centrally on the energy axis to avoid giving any clues. Many learners will draw the wrong axis, others will forget the activation energy bump.

  1. When copper sulfate undergoes electrolysis, the half equation below occurs at the negative electrode.

Cu2+ + e- Cu

(a)What word describes a reaction where electrons are gained?

(b)Complete the half equation by balancing it.

Parts (a) and (b): this is a simple recall question and balancing task. Errors here link back to ionic balancing and learners may need a revise the topic of ‘balancing charges’.

  1. Calcium carbonate will react with hydrochloric acid.

(c)Write a balanced symbol equation for this.

(d)Explain what would happen to the pH of the reaction mixture.

Part (a): this question can be quite demanding and will highlight your strongest learners. For this to be done correctly, learners will need to remember common chemical formulae, recall a common reaction and know how to balance a chemical equation.

Part (b) is testing learners’ understanding of pH and the fact that, in this experiment, the pH will increase towards 7 (i.e. neutral) as the acid is used up.

  1. Lead Bromide can be melted using a Bunsen flame.

During the electrolysis of molten lead bromide, what will be created at each electrode?

Cathode:

Anode:

Most learners should understand that the simple binary ionic compound will create lead and bromine, but they may not know how to work out which is a positive ion or which is a negative ion or may not know which electrode is which. These are all important skills to learn.

Checkpoint Task

Topic C3: Chemical reactions

Learner Activity

Answer the following questions

Use the Periodic Table to help you on some of the questions.

  1. What is the name for CO?

Put a circle around the correct answer.

carbon oxide carbon monoxide carbon dioxide

  1. Look at the two equations below.

(a)Complete the word and symbol equations.

lithium + 

Li + O2

(b)In this reaction, what is the state of lithium?

  1. Which of the following is Avogadro’s number?

Put a circle around the correct answer.

6 x103 6.02x1023 6x10-20

  1. How many moles are there in 12.15g of magnesium?

Number of moles =

  1. If 48g of magnesium reacts with 32g of oxygen, what mass of magnesium oxideis produced?

g

  1. Complete the energy level diagram for an endothermic reaction.
  1. When copper sulfate undergoes electrolysis, the half equation below occurs at the negative electrode.

Cu2+ + e- Cu

(a)What word describes a reaction where electrons are gained?

(b)Complete the half equation by balancing it.

  1. Calcium carbonate will react with hydrochloric acid.

(a)Write a balanced symbol equation for this.

(b)Explain what would happen to the pH of the reaction mixture.

  1. Lead Bromide can be melted using a Bunsen flame.

During the electrolysis of molten lead bromide, what will be created at each electrode?

Cathode:

Anode: