Chemical Recactions
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What are the 4 main factors that influence the rate of a chemical reaction?
Temperature Particle size Concentration of solute Catalyst
How does temperature influence the rate of a reaction?
An increase of temperature (heat) provides more energy which speeds up the rate of reaction due to the particles colliding and moving faster.
How does the particle size influence the rate of a reaction?
When the particle size of a reactant decreases the rate of reaction increases
How does concentration of solute influence the rate of a reaction?
Adding more reactants increases the number of collisions therefore increasing the rate of reactions
How does a catalyst influence the rate of a reaction?
Increases the speed of a reaction without changes.
What is a PH scale?
A number scale which describes how acidic will help basic substances. The scale is measured from 0 to 14.
What are acidic substances on a PH scale?
Acidic substances have a pH from 0 to 7. They are chemical compounds that release positively charged hydrogen ions (H+) or protons. When dissolved in water. Examples are lemon vinegar, hydrochloric acid and sulfuric acid.
What are base substances on an PH scale?
Best substances have a pH from 7 to 14 bases are chemical compounds that accept protons (H+) and react with acids to neutralise them forming salts and order examples of baking soda, borax, ammonia and sodium hydroxide
What is an example of a neural (7) on a PH scale?
Water
What is endothermic reactions?
A chemical or physical process that absorbs heat from its surroundings, causing the surroundings to feel colder and decrease temperature.
What is an exothermic reaction?
Releases energy, typically as heat and light into its surroundings, causing the surrounding temperature to rise.
What is the law of conservation of mass?
Mass cannot be created or destroyed but is only transformed from one form to another.
What is activation energy?
Energy needed to start a chemical reaction.
What is a decomposition reaction, provide an example.
Where a compound breaks down into 2 or more simple substances. Eg. calcium carbonate ➡️ calcium oxide + carbon dioxide
A balanced equation must have what on both sides?
Equal number of atoms
Define physical change
The appearance of a substance changes but the chemical makeup of it remains the same. No new substances are created and is often reversible.
Define chemical change
A process where one or more substances are transformed into one or more new and different substances involving the breaking of chemicals bonds and the rearrangement of atoms.
List some examples of physical change.
Mixing milk and flour- the 2 substances remain the same but have just been mixed together Sugar dissolving in water- no new substance is created, the sugar can be separated from water through things such as evaporation. Melting an ice cube- melts into liquid, no new substances are created
List some examples of chemical change
Burning paper- creates ashes Cooking an egg- protein changes shape Rusting of iron- iron oxide
Indicators of physical change examples
Change in shale such as breaking, bending, twisting, crushing and compressing
Indicators of chemical change examples
Colour change, formation of gas bubbles, heat, temperature, liquid droplets, and light.
What is the collision theory?
For a reaction to occur particles must collide with sufficient energy. Must be in the correct orientation.
What are spontaneous reactions?
A chemical reaction that occurs under its own conditions without the need of input of energy.
What are open chemical reaction systems?
An open chemical reaction system is when both matter and energy (products and reactants) can be exchanged with the surroundings