Chemical Reactions

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Edit   Delete - Last Modified By: awo at 14/07/2014 12:21:24 PM

Activity 1

Use the following equipment to show: evaporation, condensation, melting.

Equipment: Heat source, beaker, watch glass and ice.

1.       What are the key features of a physical change? 

2.       Define the following terms: melting, evaporation, condensation, freezing and sublimation.

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Complete the following experiment and then write a prac report using the headings provided.

Be sure to include a table of results and the answer the discussion and theory questions.  

Edit   Delete - Last Modified By: awo at 22/07/2014 4:28:58 PM
 

Part A: Introduction

 The atomic theory of matter was first written down by John Dalton in 1803. It states:

 

1 All matter is made up of hard, tiny, invisible particles called _________.

2 Substances made of one type of atom are called ___________. For example, the element carbon is made of carbon atoms.

3 The atoms of different elements can be distinguished by their different masses.

4 Atoms can combine to form new substances called _____________.

5 Atoms are not­­­­­_______________ or _______________ during chemical change.

 

When a chemical change occurs, the atoms in the molecules rearrange to form a different combination of atoms. This is how new substances are produced during a chemical change.

For example, when carbon (C) is burnt in oxygen gas (O2), an atom of carbon will combine with a molecule of oxygen and rearrange to form carbon dioxide gas (CO2). This is shown below.

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Recall: Complete the following

  1. If the atoms rearrange to form a new substance with a different colour, then____________________________________________ will be observed.

     

  2.  If the atoms rearrange to form a new substance that is a gas, then you will see ______________________________________.

     

  3.  If the atoms rearrange to form a new substance that is a solid, then a ____________ might be observed.

     

A chemical reaction is when atoms rearrange to form new substances.

The starting substances of a chemical reaction are known as reactants.

The substances that are formed are called products.

Word equations

The simplest way to write a chemical equation is to use the chemical names of the reactants and products.

For example, when hydrochloric acid (HCl) is mixed with sodium hydroxide (NaOH), they combine to form a solution of sodium chloride (NaCl) and water (H2O). To describe this chemical reaction with a word equationa type of chemical equation where the chemicals are represented by the chemical names, chemists write:

hydrochloric acid + sodium hydroxide -> sodium chloride + water

Formula equations

HCl + NaOH ? NaCl + H2O

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