C5 - Energy Changes

Question 1

What is ENERGY needed for?

Answer 1

Energy is needed to break CHEMICAL BONDS and is released when bonds are made.

Question 2

What is an EXOTHERMIC reaction?

Answer 2

Transfers to energy to surroundings ; temperature INCREASES.
-Products have less energy than reactants.

Question 3

Name 3 examples of an EXOTHERMIC reaction

Answer 3

Combustion, neutralisation, oxidation

Question 4

What is an ENDOTHERMIC reaction?

Answer 4

Takes in energy from surroundings ; temperature DECREASES.
-Products have more energy than reactants.

Question 5

Name an example of an ENDOTHERMIC reaction

Answer 5

Thermal decomposition

Question 6

What is ACTIVATION ENERGY?

Answer 6

Minimum amount of energy needed for particles to react.

Question 7

Describe the REQUIRED PRACTICAL - ACID AND ALKALI REACTION

Answer 7

1. Place polystyrene cup inside a glass beaker for stability.
2. Measure a suitable volume of each liquid e.g, 25cm^3
3. Place one liquid into the polystyrene cup.
4. Record temp of solution.
5. Add second liquid and record the highest and or lowest temp obtained.
6. Change the independent variable and repeat experiment.

-Independent variable may be;
-> Conc of reactant
-> Acid/alkali used
-> Metal/carbonate used.

-Wear goggles ; acids and alkalis may be irritant.

Question 8

IN A REACTION, ALL BONDS ARE

Answer 8

BROKEN, NEW ONES ARE FORMED.

Question 9

How do you calculate the NET ENERGY?

Answer 9

Sum of energy taken in - sum of energy released.