Reactions Flashcards
What are the two types of changes in reactions?
Chemical and physical changes
What are some factors of physical changes?
- no new compounds formed
- melting, boiling, freezing, condensing etc.
What are some factors of chemical changes?
- new compound formed
- Signs:
- temp change
- bubbles
- colour change
What is another word for bubbles?
Effervesces
What are the three types of variable?
Independent
Dependant
Controll
Which variable is the one that changes
Independent variable
What does the dependant variable do?
Feature that is measured
What does the control variable do?
A feature that is kept constant
Name two examples of reaction
- oxidation
- thermal decomposition
What happens to mass in chemical reactions?
It is never lost or gained (law of conservation of mass)
Define exothermic reaction
Gives out thermal energy to the environment
Does the temperature rise or fall in an exothermic reaction?
It rises and gets hot
Give two examples of exothermic reactions
Combustion and most catalysts
Define endothermic reaction
Takes in thermal energy from the environment
Which type of reaction ( endothermic or exothermic ) does the temp fall?
Endothermic
Name two examples of endothermic reactions
Thermal decomposition and ammonium nitrate
What are catalysts and what do they do?
Speeds up a reaction without being used up and provides an alternate easier pathway for reactions to occur (lowers energy for the reaction to occur)
What are the two types of catalysts?
Industrial catalysts (usually contain transitional metals)
Biological catalysts (enzymes)
Give two examples of industrial catalysts
- platinum speeds up combustion
- iron used in the Haber process
Give two examples of biological catalysts
- catalase (lipase) found in the liver
- amylase found in saliva
Define combustion
When a fuel reacts with oxygen (exothermic reaction)
What are some features of complete combustion? (
- ample oxygen present
- products = water and co2 (greenhouse gas)
What are some factors of incomplete combustion?
- little oxygen present
- products= water,Co (toxic gas), soot (can irritate the lungs if inhaled)
Give the equation for complete combustion
Fuel + oxygen ~> carbon dioxide + water
Give the equation for incomplete combustion
Fuel + oxygen ~> carbon monoxide OR Carbon + water
What is thermal decomposition?
The breakdown of a compound into similar substances due to heat
What are carbonates?
Compounds that contain carbon and oxygen
What atoms do carbonates usually consist of?
A metal, a carbon atom and three oxygen atoms (e.g CaCo3 calcium carbonate)
What do metal carbonates breakdown into?
Metal oxide and carbon dioxide
How do we test for carbon dioxide?
By bubbling gas through limewater if the limewater turns cloudy there is carbon dioxide present
What is the equation for thermal decomposition
Metal carbonate ~> metal oxide + carbon dioxide
What is another word for the clamp stand?
A retort stand
What type of tube should the horizontal test tube be?
A boiling tube
What are three safety precautions with the limewater testing?
- hair tied back
- goggles
- remove limewater before stopping heating
What 4 things do you need to do when planning an investigation?
- choose variables
- ensure control variable remains the same
- trial run
- set the interval - the size of the step between max and min
What does precision mean?
When the results are all really close together
What is an anomalous result?
When there is a result that is very different from the rest
What does it mean is something is bias?
When an experimenter has a theory that they believe is true and frames data so that their conclusion agrees with the theory
What’s an example of a bias experiment?
Tobacco companies setting experiments that minimise the signs of negative effects of smoking
What are the signs of each state?
Solid - S
Liquid - L
Gas - g
Aqueous - aq
