Atoms and Mass are conserved during a chemical reaction

SNC 2D

Balanced chemical Equation

The number of atoms as reactants must equal the number of atoms of the products.

REACTANTS PRODUCTS

2 atoms of Sodium React with 2 molecules of water

2 molecules of Sodium Hydroxide and 1 molecule of Hydrogen gas.

React to produce

Conservation of Mass

• During a chemical reaction, atoms are not created or destroyed. The atoms in the reactants are rearranged to form the new product substances.

• This fact is summarized in a scientific law called the “Conservation of Mass”.

How can this be proved?

• Experimental evidence can be measured to show that the mass of the reactants is the same as the mass of the products.

2AgNO3 + Cu Cu (NO3)2 + 2Ag

Mini Investigation

Copper(II)Chloride + Aluminum Aluminum Chloride + Copper

3Cu Cl2 + 2Al 2Al Cl3 + 3Cu

What did you observe?

• Colour change?• Change in temperature?• Bubbles of gas?• New substance(s)?

What type of reaction?

A. SynthesisB. Single displacementC. Double displacementD. Combustion

Answer: Single Displacement.

Reactivity of metals

• Metals will react/displace other metals in a certain order.

• This is called the reactivity series.

Mnemonic

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Can Metals be Active?

• Metals lose electrons to become CATIONS. Metals that lose electrons more easily will displace metals that hold on to their electrons.

• The ease with which the metal loses its electrons determines its place in the reactivity series.

• Metals that lose only one electron to achieve the stable octet tend to be more reactive.

• Potassium which loses the one electron in its valence shell to form a stable octet. Because this lone electron is further from the nucleus than the lone electron in sodium or lithium it is not held in place by the positive attractive forces of the nucleus. Remember that opposite charges attract.

• Precious metals such as gold silver and platinum cannot easily lose the required electrons to form the stable octet. Therefore they are less reactive than potassium.

Potassium Atom

Aluminum Atom

Lab Investigation

• Purpose: To prove the law of Conservation of Mass. In this lab you will carry out the following skills:1. Perform and record - carry out experiment2. Analyze and interpret – make a data table

and record observations.3. Communicate – write up a formal lab report

Formal Lab

• Must follow the correct format.• Procedure Must be written in past tense

passive tense.• NO pronouns are allowed at all in a lab report.