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We will now put our checklist into practice by looking at a reaction safe enough to try at home. Physical (the sugar grains are dispersed within the water, but the individual sugar molecules are unchanged)Ĭhemical (water vapour and carbon dioxide form)Ĭhemical (iron oxide forms - this will be discussed in more detail in Gr. Physical (air is forced into the liquid but no new substance is made) Learners only need to state physical or chemical - some explanations have been provided as background for the teacher and if you wish to explain the changes further to your learners.Ĭhemical (the egg proteins undergo a chemical change and crosslink to form a network) Interpreting, explaining chemical reactionĪctivity: Studying the fermentation reactionĪccessing and recalling information, interpretingĪctivity: Some chemical reactions from Life and LivingĪccessing and recalling information, researching, reading and writing, communicating Observing, recording information, drawing and labelling, interpretingĪctivity: Analysing the eggshell experiment

When the sludge dissolves completely, simply add more solid Ca(OH) 2.ģ.1 How do we know a chemical reaction has taken place? (1.5 hours)Īctivity: The difference between physical and chemical changesĪccessing and recalling information, sorting and classifying,Īctivity: Can we use a chemical reaction to see inside an egg? To make more, simply add more water, shake it up and let it settle again. The clear liquid above the solid Ca(OH) 2 is a saturated solution of Ca(OH) 2, also known as clear limewater.Ĭarefully decant as much of this as you need, without stirring up the solid Ca(OH) 2 sludge at the bottom. Leave the suspension to settle for a few days. Shake or stir to make a cloudy suspension. Place a few tablespoons of calcium hydroxide, Ca(OH) 2, in a clear 500 ml reagent bottle and fill with water. To make clear limewater follow the instructions below: It is also a good idea to make the limewater needed for the investigation 'Can clear limewater be used to detect carbon dioxide?'before you start this chapter. It will help to show learners that chemical change is usually observable on the macroscopic scale and that macroscopic observations provide evidence of activity on the level of particles. It is suggested that you start with it during the first lesson of this chapter. The activity 'Can we use a chemical reaction to see inside an egg?'takes a few days. Learners will also be given an opportunity to draw such diagrams themselves in the activities and review questions of this chapter. To help learners make this important conceptual connection, particle diagrams are used to represent some of the reactions in this chapter. That means that the molecules change, even though the number of each kind of atom present at the start of the reaction, stays the same throughout. The atoms do not change, but how they are arranged in relation to each other does change.

The important message of this chapter is that atoms are rearranged during a chemical reaction. 8 Matter and Materials, specifically the paragraph Pure Substances. This chapter builds on the brief introduction to chemical reactions that was covered in Chapter 1 (Atoms) of Gr.