Year 10 Chemistry: Chemical Reactions and Equations Review

Chemical change evidence

New substance formed, colour change, energy/temperature change, gas produced, light emitted.

Reactants and products

Reactants on the left side of the arrow, products on the right.

Combustion reaction equation

Metal element + Oxygen → Metal oxide.

Hydrocarbon combustion equation

Hydrocarbon + Excess oxygen → Water + Carbon Dioxide.

Decomposition reactions

Decomposition reactions are when a substance breaks down into simpler molecules or atoms.

Combination reactions

Combination reactions is when multiple elements or compounds bond to create a more complex product.

Combination reaction example

2Mg + O2 → 2MgO.

Decomposition reaction example

2H2O → 2H2 + O2.

Testing for carbon dioxide

Hold a flame up to a test tube containing the trapped gas, if it goes out then it is carbon dioxide.

Formation of precipitates

When two aqueous solutions are dissolved in water, they break apart as each atom gets surrounded by many water molecules.

Solubility rules for precipitates

Basically anything containing Sodium or nitrate is soluble. Most compounds containing sulfur, carbonate, or hydroxide are insoluble and will form precipitates.

Balanced formula equations for precipitation

Make sure the same number of each atom is on both sides. If no precipitate is formed, write no reaction.

Conservation of mass in reactions

Balanced chemical equations demonstrate the law of conservation of mass as the number of atoms on both sides are the same as matter cannot be created or destroyed.

Writing balanced equations

Make sure same number of atoms on each side.

State of reactants and products

Most acids and bases are aqueous. Most metals are solids.

Ammonium

NH4 +

Carbonate

CO3 2-

Nitrate

NO3 -

Hydroxide

OH -

Sulfate

SO4 2-

Water

H2O

Carbon Dioxide

CO2

Methane

CH4

Oxygen

O2

Hydrogen

H2

Nitrogen

N2

Carbon Monoxide

CO

Hydrochloric Acid

HCl

Nitric Acid

HNO3

Sulfuric Acid

H2SO4

Acid + Base

Salt + Water

Acid + Metal

Hydrogen + Salt

Acid + Metal Carbonate

Salt + Water + Carbon dioxide

Hydrogen gas test

If it makes a pop sound it is Hydrogen.

Oxygen gas test

If it burns quicker, almost like a combustion then it is Oxygen.

Carbon Dioxide gas test

If the match goes out then it is Carbon Dioxide.

Activity Series of Metals

The more solutions a metal reacts with, the more reactive it is.

Metal Displacement Reactions

Whichever metal is more reactive will be part of the compound.

Aim of Experiment

State purpose of experiment, beginning with something like 'To determine if Independent Variable will cause Dependent Variable to change.'

Hypothesis

If independent variable is changed, then the dependent variable will increase/decrease because of scientific reasoning.

Table of Results

Independent variable goes on left side, keep same number of decimal places throughout measurements.

Graph of Results

Usually use line graph to show continuous data, don't go through each individual point, just to line of best fit with same number of dots above and below.

Anomalies and Errors

Anomalies are data points that don't match the general rule, errors can include: Systematic Error, Random Error, Human Error.

Precision

How similar results are each time and consistent.

Accuracy

How close the results are to the true answer.

Repeatability

Experiment can be repeated by same people with same equipment to get the same results.

Reproducibility

Different people using different equipment somewhere else do the experiment and get the same results.

Conclusion

Say if the hypothesis was supported or not and summarize key findings.