NATURAL SCIENCE GRADE 8 EXAM
QUESTIONS WITH CORRECT ANSWERS
What is a chemical change? - ANSWER-When 2 or more elements or compounds
interact and the properties of the molecules change. New substances are formed but
this is irreversible!
Reactants - ANSWER-Substances that combine in a chemical reaction
Products - ANSWER-Substances that are formed after a chemical reaction has taken
place
E.g. sodium + chlorine= sodium chloride
What is a physical change? - ANSWER-Particles in a compound change their
arrangement but can be reversed. No new substances are formed
Example of physical change - ANSWER-Heating ice to liquid water, substance still
WATER so no substances formed
Proton - ANSWER--positive charge
-larger/ heavier than electrons
-located in nucleus of atom
Neutron - ANSWER--neutral
- no electrical charge
- large and heavy
- located in nucleus
Electron - ANSWER--negatively charged
- tiny, light particles
-move around nucleus
What is the nucleus? - ANSWER-The central region of the atom
What is a nucleon? - ANSWER-Made up of proton and neutron
What is the atomic mass? - ANSWER-number of protons plus neutrons
How do you calculate neutrons? - ANSWER-Atomic mass - atomic number= neutrons
True or False: electrons = protons - ANSWER-True
Photosynthesis - ANSWER-Chemical process in which green plants use energy in
sunlight to convert carbon dioxide and water into glucose
, Chlorophyll - ANSWER-Green pigment found in the chloroplast
Chloroplast - ANSWER-An organelle found in plant and algae cells where
photosynthesis occurs
What are the requirements for photosynthesis? - ANSWER-1. Glucose( main product
and type of sugar)= food for animals
2. Oxygen ( by product and released into air)= breathe d by animals
How does photosynthesis work? - ANSWER-Carbon dioxide and water react to form
glucose and oxygen but chlorophyll and sunlight is needed for the reaction to occur
What happens to the make product(glucose) ? - ANSWER-Plants use it to help with
their life processes. Some is broken down to release energy and the rest is changed
into compounds
What are the three types of sugar? - ANSWER-Sucrose, Starch and Cellulose
Sucrose - ANSWER--2 sugar molecules joined
- form in which sugar is transported from one part of a plant to another
Starch - ANSWER--long chain of glucose molecules joined
- main form in which plants store energy
Cellulose - ANSWER--made up of linear chains of sugar
- provides structure and support in plants
What is cellular respiration? - ANSWER-Process in which sugars are converted into
usable energy(ATP)
Where does cellular respiration take place? - ANSWER-In the mitochondria in plants
and animals cells
What are the requirements for cellular respiration? - ANSWER-Glucose and oxygen
What happens during cellular respiration? - ANSWER-Glucose and oxygen react to
form water,carbon dioxide and energy(ATP)
What are the products of cellular respiration? - ANSWER-Energy, Carbon dioxide and
water
How do you test for a product of respiration? - ANSWER-Testing exhaled air for the
presence of carbon dioxide is a simple test for presence of respiration
What are the 7 life processes? - ANSWER-Movement
Respiration
QUESTIONS WITH CORRECT ANSWERS
What is a chemical change? - ANSWER-When 2 or more elements or compounds
interact and the properties of the molecules change. New substances are formed but
this is irreversible!
Reactants - ANSWER-Substances that combine in a chemical reaction
Products - ANSWER-Substances that are formed after a chemical reaction has taken
place
E.g. sodium + chlorine= sodium chloride
What is a physical change? - ANSWER-Particles in a compound change their
arrangement but can be reversed. No new substances are formed
Example of physical change - ANSWER-Heating ice to liquid water, substance still
WATER so no substances formed
Proton - ANSWER--positive charge
-larger/ heavier than electrons
-located in nucleus of atom
Neutron - ANSWER--neutral
- no electrical charge
- large and heavy
- located in nucleus
Electron - ANSWER--negatively charged
- tiny, light particles
-move around nucleus
What is the nucleus? - ANSWER-The central region of the atom
What is a nucleon? - ANSWER-Made up of proton and neutron
What is the atomic mass? - ANSWER-number of protons plus neutrons
How do you calculate neutrons? - ANSWER-Atomic mass - atomic number= neutrons
True or False: electrons = protons - ANSWER-True
Photosynthesis - ANSWER-Chemical process in which green plants use energy in
sunlight to convert carbon dioxide and water into glucose
, Chlorophyll - ANSWER-Green pigment found in the chloroplast
Chloroplast - ANSWER-An organelle found in plant and algae cells where
photosynthesis occurs
What are the requirements for photosynthesis? - ANSWER-1. Glucose( main product
and type of sugar)= food for animals
2. Oxygen ( by product and released into air)= breathe d by animals
How does photosynthesis work? - ANSWER-Carbon dioxide and water react to form
glucose and oxygen but chlorophyll and sunlight is needed for the reaction to occur
What happens to the make product(glucose) ? - ANSWER-Plants use it to help with
their life processes. Some is broken down to release energy and the rest is changed
into compounds
What are the three types of sugar? - ANSWER-Sucrose, Starch and Cellulose
Sucrose - ANSWER--2 sugar molecules joined
- form in which sugar is transported from one part of a plant to another
Starch - ANSWER--long chain of glucose molecules joined
- main form in which plants store energy
Cellulose - ANSWER--made up of linear chains of sugar
- provides structure and support in plants
What is cellular respiration? - ANSWER-Process in which sugars are converted into
usable energy(ATP)
Where does cellular respiration take place? - ANSWER-In the mitochondria in plants
and animals cells
What are the requirements for cellular respiration? - ANSWER-Glucose and oxygen
What happens during cellular respiration? - ANSWER-Glucose and oxygen react to
form water,carbon dioxide and energy(ATP)
What are the products of cellular respiration? - ANSWER-Energy, Carbon dioxide and
water
How do you test for a product of respiration? - ANSWER-Testing exhaled air for the
presence of carbon dioxide is a simple test for presence of respiration
What are the 7 life processes? - ANSWER-Movement
Respiration
