Natures Chemistry Unit 2

Question 1

What is a fuel?

Answer 1

Fuels are substances which, when burned, give out energy.

Question 2

The fire triangle

Answer 2

The fire triangle shows the 3 things a fire needs to burn.

The 3 sides to a fire triangle is HEAT, FUEL and OXYGEN.

A fire can be extinguished by removing one side of the fire triangle.

Question 3

Exothermic

Answer 3

A reaction which releases heat energy. Combustion of fuels is an example of this.

Question 4

Endothermic

Answer 4

A reaction which absorbs heat energy.

Question 5

Oil formation

Answer 5

Millions of years ago plants and sea animals died and were covered by sand and mud.

The dead plants and animals were buried deeper and deeper under the layers of sand and mud over millions of years.

Eventually the layers of sand and mud were compressed into solid rock.

The pressure from the rock above and the heat from the earth slowly changed the dead plants and animals into oil and natural gas.

Question 6

Crude oil

Answer 6

Crude oil and natural gas are made from a complex mixture of hydrocarbons.

Crude oil isn’t very useful in this form but it can be separated into groups of useful hydrocarbons or FRACTIONS.

Question 7

Renewable energy sources

Answer 7

• Solar power
• Wind turbines
• Wave and tidal
• Biomass
• Bioalcohols
• Nuclear
• Hydrogen

Question 8

Respiration

Answer 8

All living things need energy to survive. The energy producing reaction is known as respiration.

Respiration uses a type of carbohydrate called GLUCOSE as a fuel.

Carbohydrates come from plants. They make them by photosynthesis.

Glucose+O2
—————>
(Exothermic reaction)
CO2+H2O

Question 9

Photosynthesis word equation

Answer 9

CO2+H2O
——————>
(Plant needs sun’s energy and chlorophyll found in plant cells).
Glucose+O2

Question 10

Testing for fat

Answer 10

There are 2 ways to test for fat:
Filter paper
Ethanol

The ethanol turned cloudy when we added vegetable oil. The crisps and oil turned the filter paper translucent.

Question 11

Testing for Vitamin C and protein

Answer 11

DCPIP(dark blue) is used to test for Vitamin C.

Biuret is for testing protein.

Question 12

Fermentation

Answer 12

Fermentation is the process which changes sugar solutions into alcohol solutions.

The fermentation reaction produces alcohol and carbon dioxide.

Glucose
————>
(Enzymes in yeast)
Alcohol + carbon dioxide

Question 13

Growing plants

Answer 13

Fertilisers are chemicals which are used to promote crop growth.
Fertilisers assist with food production by making plants grow faster and bigger.

Essential elements:
Nitrogen
Phosphorus
Potassium

Fertilisers are often loaded with 2 or more if these elements as they are essential for healthy plant growth.

Question 14

Effects of alcohol

Answer 14

Can be addictive and be very hard to give up.

Causes drunkness, dizziness and even unconsciousness if too much is drunk.

Over time can cause permanent liver damage.

Human health
Cancer
Gut and pancreas disorders 
Brain damage
Damage to nervous tissue

Question 15

Electrical fire and frying pan fire

Answer 15

The way to extinguish an electrical fire is to take away the oxygen by using a foam or CO2 extinguisher.

The way to extinguish a fire in a frying pan is to take away the oxygen.

Question 16

Separating oil

Answer 16

We can separate oil into fractions by boiling the oil at different temperatures and different things come out.

Question 17

Fermentation experiment

Answer 17

A balloon is put on top of a conical flask that contains glucose water and yeast.

The alcohol produced by fermentation is a watery mixture of not more than 14% alcohol, probably less.

Drinks such as whisky and gin require a greater concentration of alcohol.

This is achieved by distilling the mixture.

Question 18

Distilling the mixture

Answer 18

The alcohol mix is put in a round bottomed flask on a hot plate with a thermometer in the top.

The mixture then evaporates into a condenser where it is turned back into liquid using water.

The liquid then runs into a flask where it has now been turned into purified alcohol.

Question 19

Boiling Points

Answer 19

Alcohol b.p. = 79 degrees C

Water b.p. = 100 degrees C

Question 20

Glucose and starch

Answer 20

Glucose is a simple sugar (carbohydrate) made by plants.

Starch is a complex carbohydrate formed when many glucose molecules join together.

Question 21

Test for glucose

Answer 21

There are two test tubs, one half filled with water and one with water and glucose.

Both have 3 drops of Benedict’s solution and are put in a beaker of hot water (70 dC).