bbc bitesize Calorimetry
Which of the following must be kept the same in order to ensure a fair test when investigating the energy given off by different fuels when they burn?
If the same volume of water is used for each fuel and it is at the same starting temperature, then the results can be analysed to find out which fuel releases the most energy. It shouldn't matter who reads the thermometer.
When investigating energy changes in neutralisation reactions why is a polystyrene cup used instead of a glass beaker?
,Expanded polystyrene cups are very good thermal insulators, which prevents heat from being lost through the sides of the cup. They are less stable than beakers and care must be taken to stop them falling over.
What name is given to a small metal can used to hold water that is heated by a chemical reaction?
A calorimeter is a special type of beaker that is made from metal (usually copper). A burette is used to measure volumes of liquids precisely.
What piece of apparatus is used to burn an alcohol in an controlled way during a calorimetry experiment?
A spirit burner is used to burn liquid alcohols in a controlled way.
Which is an example of an endothermic reaction?
Chemical ice packs feel cold to the touch because they are absorbing heat energy from your skin. Respiration releases energy so it is exothermic.
Which is an example of an exothermic reaction?
Combustion reactions release large amounts of energy, so they are exothermic. Photosynthesis requires lots of sunlight, so it is endothermic.
Exothermic reactions can release energy in a number of ways. Which of these is a way that an exothermic reaction might release its energy?
Electricity can be generated by chemical reactions. For example, putting a copper and a zinc electrode into a lemon and connecting them via a voltmeter. Chemical reactions do not release gravitational potential energy.
What term is used to describe chemical reactions that absorb heat energy from the surroundings?
Endothermic reactions absorb heat from the surroundings. They are not as common as exothermic reactions.
In the laboratory how can you tell if a reaction is exothermic?,
Exothermic reactions transfer energy to the surroundings, usually as heat, so there is normally a temperature rise which can be measured using a thermometer. A temperature decrease identifies an endothermic reaction.
What is the biggest source of error in calorimetry experiments?
loss is the biggest source of error in calorimetry experiments. It is important to use the thermometer carefully, but it is rarely the source of a large amount of error.