C3a

Question 1

What is an exothermic reaction?

Answer 1

• energy is given out to the surroundings

- usually a form of heat, which is shown by a rise in temperature

Question 2

What is an endothermic reaction?

Answer 2

• energy is taken in from surroundings

- usually in the form of heat, which is shown by a fall in temperature

Question 3

How can you decide if reaction is exo or endo?

Answer 3

• temperature change
• in a chemical reaction you can tell by taking temperature of reactants, mixing them in polystyrene cup and measuring the temperature of the solution

Question 4

Give examples of endothermic reaction?

Answer 4

-adding acid to an alkali

Question 5

Give examples of exothermic reactions?

Answer 5

-dissolving ammonium nitrate in water

Question 6

What is the relation between bonds and endothermic reaction?

Answer 6

-the energy required to break bonds is greater than the energy released when new bonds are formed

Question 7

What is the relation between bonds and exothermic reactions?

Answer 7

-energy released in bond formation is greater than the energy used to break old bons

Question 8

How can you calculate energy transferred?

Answer 8

• you can calculate energy supplied per gram of fuel if you know:
• how much fuel you burnt
• temperature change of water
• water s.h.c
• mass of water
• doing the same experiment with different fuels allows you to compare the energy transferred per gram

Question 9

What is the process of the calorimetric method?

Answer 9

1-put fuel in spirit burner and weigh the burner full of fuel
2-measure 200cm3 of water into a copper calorimeter
3-take initial temperature of water
4-put burner under calorimeter and light wick
5-heat until temperature rises between 20-30C
6-blow out spirit burner and note the highest temperature water reached
7-reweigh burner and fuel
8-if comparing two fuels, repeat withe second fuel