Air and Photosynthesis

Question 1

Air is (1). It is made up of (2).

Answer 1

1) a mixture of gases

2) nitrogen, oxygen, carbon dioxide, noble gases, water vapour and small amounts of other gases.

Question 2

The percentages of gases in the air:

Answer 2

Nitrogen: 78%
Oxygen: 21%
Noble gases: 0.9%
Water vapour and other gases: 0.07%
Carbon dioxide: 0.03%

Question 3

Noble gases and nitrogen are (1).

Answer 3

1) unreactive gases

Question 4

Facts about oxygen:

Answer 4

Colourless
Odourless
Burning splint test: burns more brightly
Glowing splint test: relights

Question 5

Facts about carbon dioxide:

Answer 5

Colourless
Odourless
Colour change of hydrogencarbonate indicator: from red to yellow
Colour change of lime water: from colourless to milky

Question 6

Hydrogencarbonate indicator is used to measure (1) and give different (2) at different (3).

Answer 6

1) carbon dioxide levels
2) colours
3) carbon dioxide concentrations

Question 7

Colour of hydrocarbonate indicator to concentration of carbon dioxide:

Answer 7

> 0.03%: yellow
0.03% (normal level in air): red
<0.03%: purple

Question 8

(1) is used to test for water and water vapour. (1) should be stored in a (2) which contains (3) to (4).

Answer 8

1) dry cobalt chloride paper
2) desiccator
3) chemicals
4) absorb moisture

Question 9

Water and water vapour turn (1) from (2) to (3).

Answer 9

1) dry cobalt chloride paper
2) blue
3) pink

Question 10

(1) plants can make their own food by (2). This process needs (3) to make food. (4) is also produced as a (5) in the process.

Answer 10

1) Green
2) photosynthesis
3) raw materials and an energy source
4) Oxygen
5) by-product

Question 11

(1) and (2) are the raw materials for photosynthesis. (1) is (3) from the (4). (2) is (5) from the (6).

Answer 11

1) Carbon dioxide
2) water
3) obtained
4) air
5) absorbed
6) soil

Question 12

Energy needed for photosynthesis comes from (1). The (1)(2) is absorbed by (3), a (4) in the (5) or (6). During photosynthesis, (1)(2) is (7) into (8)(2) in the (9) produced.

Answer 12

1) light
2) energy
3) chlorophyll
4) green pigment
5) chloroplasts of green leaves
6) other green parts of plants
7) converted
8) chemical
9) food

Question 13

(1) is the food produced. The plants use (1) for (2). (1) that is not used immediately is (3) into (4) for (5). (4) can be (3) back into (1) for use later. Both (1) and (4) are (6).

Answer 13

1) Glucose
2) growth and respiration
3) converted
4) starch
5) temporary storage
6) carbohydrates

Question 14

The word equation of photosynthesis:

Answer 14

carbon dioxide + water (reactants) —> glucose (product) + oxygen (by-product)
\
\
light energy absorbed by chlorophyll

Question 15

Chemical equation of photosynthesis:

Answer 15

6CO2 + 6H2O —> C6H12O6 + 6O2

Question 16

From the chemical equation, we can see that:

Answer 16

• carbon dioxide reacts with water to form glucose and oxygen.
• the total number of each atom (carbon atom, oxygen atom and hydrogen atom) is the same on both sides of the equation.

Question 17

We (1) a plant carrying out photosynthesis. However, (2) can provide (3) of photosynthesis. If we can show from (2) that the plant has (4), we can confirm that photosynthesis has taken place.

Answer 17

1) cannot see
2) experiments
3) evidence
4) produced starch and oxygen

Question 18

Procedures of starch test:

Answer 18

1) Remove a leaf from a potted green plant that has been placed in bright light for several hours.
2) Put the leaf into a beaker of boiling water for about two minutes. This destroys the cell membranes of the leaf cells.
3) Turn off the Bunsen burner. Use a pair of forceps to transfer the leaf to a boiling tube containing alcohol. Then, put the boiling tube into the beaker of hot water for about 10 minutes.
4) Use a pair of forceps to remove the leaf from the alcohol. Wash the leaf in the beaker of hot water for about 30 seconds. This removes the alcohol and makes the leaf soft.
5) Use a pair of forceps to take the leaf out of the hot water and carefully spread it on a white tile. Add a few drops of iodine solution to it.

Question 19

We can use (1) to test for starch. (1) changes from (2) to (3) in the (4) of starch.

Answer 19

1) iodine solution
2) brown
3) blue-black
4) presence

Question 20

In addition to starch, (1) is also produced in photosynthesis. We can use a (2) to show that the (3) given out by the plant is (1). If the (2)(3), the (3) given out by the plant is (1), (4) that photosynthesis has taken place.

Answer 20

1) oxygen
2) glowing splint
3) gas
4) indicating

Question 21

Explanation for destarching a plant:

Answer 21

Destarching means placing a plant in the dark for at least 48 hours. During this period, all the starch stored in the plant is converted into glucose which is then used by the plant. This ensures that the plant does not contain any starch when the investigation begins. Any starch we detect later is formed during the investigation, indicating that photosynthesis has taken place.

Question 22

What is soda lime used for?

Answer 22

Absorbing carbon dioxide.

Question 23

Photosynthesis is an (1). It allows plants to (2). On the other hand, (3) cannot (2). Some (3) feed on plants and other (3) feed on (3). Therefore, photosynthesis is important in (4). Photosynthesis also helps (5) in Nature.

Answer 23

1) essential life process
2) make their own food
3) animals
4) providing food directly or indirectly for living things
5) maintain the balance of oxygen and carbon dioxide

Question 24

Plants can (1) by (2). They are called (3). Animals cannot (4). They (5). They are called (6). The (7) among (8) can be shown by a (9).

Answer 24

1) make their own food
2) photosynthesis
3) producers
4) produce food on their own
5) feed on plants or other animals
6) consumers
7) feeding relationship
8) living things
9) food chain

Question 25

Explain the following food chain:

grass —> grasshopper —> bird

Answer 25

In the above example, grass converts the light energy from the Sun into chemical energy which is stored in the food produced. This energy is then transferred to the grasshopper and then to the bird through feeding. In this way, energy can flow through the ecosystem. The arrows in the food chain show the direction of the flow of energy.

Question 26

Since plants make use of the (1) from (2) to carry out (3),(2) is the (4) for all (5).

Answer 26

1) light energy
2) the Sun
3) photosynthesis
4) ultimate source of energy
5) food chains