Science Flashcards
What is variation?
the differences that occur between different species and within the same species
What is variation caused by?
genetics and the environment
What are inherited variations?
these are inherited characteristics from parents e.g. facial features, height, hair colour, eye colour
What are environmental variations?
traits that are influenced by the environment e.g. hair length, language, strength
Do you think skin colour is an inherited or environmental characteristic?
Both - a child will have similar skin colour to its parents, but it can change with sun exposure
What are the 4 features that are truly inherited (and not affected by the environment)?
natural eye colour
natural hair colour
blood group
inherited disease
Most features are caused by both inherited and environmental factors, true or false?
True
What is continuous variation?
a feature that can take on any value in a range e.g. height can be anything from the smallest human possible to the tallest human possible
What is discontinuous variation?
a feature that can only have certain values e.g. eye colour can only be brown. blue or green. Another example is blood type
True or false - identical twins are genetically identical
True - identical twins come from a single egg and sperm
Do non-identical twins come from the same egg?
No - they come from 2 separate eggs fertilized by different sperm
What makes organisms different from each other?
DNA - DNA is unique to that organism. Except for identical twins, they have identical DNA
Where is DNA located?
at the nucleus of cells and they are tightly coiled into packages called chromosomes
What is a gene?
a particular section of DNA
How many chromosomes do humans have?
most human body cells contain 46 chromosomes - they are matched up as 23 pairs
Who do people inherit chromosomes from?
half from mother, half from father
What does a gene control?
separate characteristics e.g. eye colour
What do proteins do?
they perform many roles in the body
What type of protein forms cells and tissues?
Structural protein
What type of protein carries out reactions in the body?
functional proteins
Give 2 examples of structural proteins
collagen (found in many human tissues)
cellulose (found in plant cells)
Give an example of a functional protein
Enzymes
What do enzymes do?
they catalyze (cause) reactions
We may look similar to our parents, but our characteristics will not be exactly the same. Why?
- Because when sex cells are produced (gametes), genes are swapped between the chromosomes so that they are not the same as the parent cell
- At fertilisation, any sperm could fuse with the egg, mixing the genes from both parents
We may look similar to our parents, but our characteristics will not be exactly the same. What is this called?
genetic variation
What is another cause of genetic variation?
mutation
What is a mutation?
where there is a change in the type or amount of DNA
When do mutations occur?
- When DNA is not copied correctly during replication
- when chromosome pairs divide unequally during cell division
Give some examples of mutations that can be caused by environmental factors
- radiation, such as UV radiation
- exposure to certain chemicals
(these factors are called mutagens)
Is body mass (your weight) determined by genes or the environment?
both - it is inherited but is also affected by how much you eat and exercise
What must occur for a woman to become pregnant?
fertilisation
What is fertilisation?
The fusing of an egg and a sperm cell. The sperm’s nucleus will join the egg’s nucleus
How often do females produce an egg?
approximately every 28 days
What is ovulation?
When a female produces an egg (every 28 days)
How often do males produce sperm in the testes?
continually
What are the 5 stages of fertilisation?
1 - ovulation (egg is released from the ovary)
2 - sperm is released into the vagina and travels to the oviduct
3 - the nucleus of a sperm and egg fuse together to produce a zygote
4 - the fertilised egg travels to the uterus and embeds itself into the lining
5 - the fertilised egg is now called an embryo - the lining of the uterus develops into the placenta for nourishing the embryo into a fetus
What is the name given to a male gamete?
Sperm
Where does the female egg cell implant after fertilisation?
Uterus lining
True or false - there is no mixing of maternal and fetal blood in the placenta
True
Where does fertilisation occur?
In the Oviduct
True or False - egg cells have a tail?
False
What is the name given to a female gamete?
Egg cell
Which substance can diffuse across the placenta from mother to fetus?
Glucose
What is a zygote?
A fertilised egg cell before it has divided into an embryo
What is the placenta?
an organ that grows into the wall of the uterus and is joined to the fetus by an umbilical cord
What does the placenta do?
allows the exchange of oxygen and nutrients (such as glucose) between the fetus and mother and removes waste such as carbon dioxide and urea
How does the placenta exchange materials between the fetus and mother?
by diffusion
What are the 2 functions of the ovaries?
- contain eggs
- make female hormones which affect the way the body develops and regulates menstrual cycle
How long does it take for a fetus to develop and what is this time called?
40 weeks, gestation period
What happens during birth?
the cervix relaxes and the muscles in the wall of the uterus contract. Waves of muscle contractions push the baby out of the vagina
which part of the female reproductive system is immediately above the vagina?
the cervix
Which part of the male reproductive system holds the testes?
the scrotum
Which terms describes the time between pregnancy and birth?
Gestation
When an egg cell joins a sperm this is called..
fertilisation
A fertilised egg divides to form a ball of cells called…
An embryo
Which substances does not move through the placenta to the fetus:
- nutrients
- oxygen
- carbon dioxide
Carbon dioxide
What is the role of the testes?
they produce sperm and the hormone testosterone
Which tube carries urine out of the body in the male and female reproductive systems?
the urethra
What is photosynthesis?
Plants make their own food using photosynthesis. They do this by producing glucose and oxygen from carbon dioxide and water
What is the word equation for photosynthesis?
Carbon dioxide + Water (then chlorophyll absorbs light) = Glucose + Oxygen
What type of reaction is photosynthesis?
Endothermic
What is chlorophyll?
the green chemical inside the chloroplasts of plant cells
What does chlorophyll do and where is it located?
It is in the leaves and it absorbs light
How does carbon dioxide enter the plant for photosynthesis?
carbon dioxide comes from the air and it enters the leaves through the stomata
How does water enter the plant?
Through the roots
What happens to the oxygen and glucose made during photosynthesis?
the plant releases oxygen into the air, glucose is used to make cell walls and makes the plant grow
What does a plant need for photosynthesis to happen?
- Water
- Carbon dioxide
- light
How does light affect photosynthesis?
Without enough light, a plant cannot photosynthesise very quickly - even if there is plenty of water and carbon dioxide
What is selective breeding in plants?
An artificial process in which humans choose the characteristics to grow e.g. for crops
How does selective breeding happen?
Humans choose the best plants to breed together to produce the next crop, they repeat this process over many generations to get the desired plant (can also be done for cattle to produce the best meat)
What types of plants do humans choose for selective breeding?
- disease resistant crops
- wheat plants that produce lots of grain
- large or unusual flowers
What types of animals do humans choose for selective breeding?
- animals that produce lots of milk or meat
- chickens that lay large eggs
What are the benefits of selective breeding?
can produce more or better quality food
What are the risks of selective breeding?
- reduced genetic variation which can lead to specific problems e.g. can lead to attack by insects (for plants), or in animals it can create physical problems like deafness or bad hips in dogs
What is a pH scale?
Used to measure acidity and alkalinity
What can chemicals be classified as in a pH scale?
Acid
Neutral
Alkaline
What does an acid form when it is neutralised?
a salt
What are pH indicators?
They are substances that change colour when they are added to acidic or alkaline solutions
What type of solution has a pH scale of less than 7?
Acidic
What type of solution has a pH of 7?
Neutral
What type of solution has a pH scale greater than 7?
Alkaline
What colour does a universal indicator change to for a strong acid?
Red
What colour does a universal indicator change to for a weak acid?
Yellow or orange
What colour does a universal indicator change to for a neutral solution?
green
What colour does a universal indicator change to for a strong alkaline?
dark blue
What colour does a universal indicator change to for a weak alkaline?
light blue
When an acid is dissolved in water what does it produce?
Hydrogen ions (protons)
When alkalis are dissolved in water what do they produce?
hydroxide ions
What is a base?
chemical opposite of an acid
What happens when an acid is mixed with an alkaline
a neutralisation reaction occurs to form water
Which of the following could have a pH of 12?:
- Sodium Chloride
- Sulfuric acid
- Sodium Hydroxide
Sodium Hydroxide
What is neutralisation?
when an acid reacts with a base or alkali to form salt and water
What is rust?
when a metal object (like Iron) is exposed to open air and bad weather it corrodes
What causes rust?
Air
Moisture
Salt water
How can rust be prevented?
Can stop air and water reaching the metal by:
- painting it
- greasing it
- covering it in a more reactive metal e.g. with zinc (galvanise)
- covering it in a less reactive metal e.g. gold, silver (electroplating)
What are the indicators that a chemical reaction has taken place?
- a change of colour
- a change of temperature
- the production of a gas or solid (effervescence / precipitation)
What affects the rate (speed) of a chemical reaction?
- temperature
- concentration
- particle size
- presence of a catalyst
What is a chemical reaction?
When one or more substances change and produce one or more new chemical substances
What are the substances that are changed by a chemical reaction called?
Reactants
What are the substances that are produced by a chemical reaction called?
products
A colour change might take place when two substances react. It can also happen when a compound is broken down by heating it. What is this called?
Thermal decomposition
Effervescence is an indicator that a chemical reaction has taken place. How does this show in a liquid?
Bubbles of gas in the liquid
In an exothermic reaction the reactants hold more energy than the products, so exothermic reactions release energy in the form of heat. How do we know if an exothermic reaction has taken place?
there is an increase in temperature
Endothermic reactions take in heat. How do we know if an endothermic reaction has taken place?
decrease in temperature
Chemical reactions always form new substances. True or False?
True
Different chemical reactions occur at different rates or speeds. Some are very slow, like a car rusting, while others are very fast like a sudden explosion. What 4 factors affect the rate (speed) of a chemical reaction?
- temperature
- concentration
- particle size
- use of a catalyst
What is a catalyst?
- something that speeds up a reaction
- is not changed after the reaction has finished
When a substance burns, it reacts with oxygen in the air. What is this known as?
Combustion
All combustion reactions are exothermic. True or False?
True - they release heat
What is a displacement reaction?
When a more reactive metal displaces a less reactive metal from its compound
What is a reactivity series?
a list of metals from the most reactive at the top to the least reactive at the bottom
What can a reactivity series be used for?
to predict displacement reactions
Can a displacement reaction take place if there is no difference between the reactivity between 2 metals?
No -
Aluminium is more reactive than iron. This means the aluminium takes the oxygen from the iron oxide to produce what?
Aluminium oxide
Iron is dipped into a copper sulfate solution. The products are iron sulfate and copper. Is iron or copper the more reactive metal?
This shows that iron is the more reactive metal.
When displacement reactions occur, the temperature rises. The larger the temperature rise, the higher the metal is in the reactivity series. True or False?
True
Which metal would not be included in an experiment using copper sulfate solution to determine a reactivity series?
- Copper
- Aluminium
- Zinc
Copper - because they have to be different metals to be able to react
What is a chemical change?
When a chemical reaction occurs and a new chemical element or compound is formed
What is a physical change?
when a substance changes its physical state e.g. from a solid to a liquid
What is the difference between a chemical and physical change?
A physical change does not lead to a new chemical substance forming
Which state of matter has particles that are tightly packed in a regular arrangement?
- Gas
- Liquid
- solid
Solid
Which state of matter has particles with the highest energy?
- Gas
- Liquid
- Solid
Gas
Which term is used for the change of state from solid to liquid?
- Boiling
- Freezing
- Melting
Melting
What happens during sublimation?
- a solid turns to a liquid
- a liquid turns to a gas
- a solid turns to a gas
A solid turns to a gas
Which states of matter can be compressed?
- Gas only
- Gas and liquid
- Liquid only
Gas only
Which state of matter has particles that are furthest apart?
- Gas
- Liquid
- Solid
Gas
What happens to the energy of gas particles when they condense to a liquid?
- The particles gain energy
- The particles lose energy
- The particles have the same energy
The particles lose energy
Why are solids difficult to compress?
- The particles are very large
- The particles have high energy
- The particles are very close together
The particles are very close together
Why do some collisions between particles not lead to a reaction? - Higher
- The particles have too little energy
- The particles have too much energy
- The particles are strongly attracted to each other
The particles have too little energy
What elements are placed on the left-hand side of the periodic table?
Metals
What elements are placed on the right-hand side of the periodic table?
Non-metals
What are the typical properties of metals?
- shiny
- high melting points
- good conductors of electricity
- good conductors of heat
- high density
- malleable and ductile (can change its shape without breaking)
Metals and non-metals can react with oxygen to make compounds called what?
Oxides
Metal oxides are bases. What does this mean?
That they can neutralise an acid
Non-metal oxides dissolve in water to make acidic solutions. True or False?
True
Compounds are substances made of two or more types of atoms chemically bonded together. All oxides are compounds, and contain a single element bonded with oxygen. What compound does Magnesium and Oxygen make?
Magnesium Oxide
What does the ‘mon’ in Carbon Monoxide mean?
that it has 1 oxygen atom
What does the ‘di’ in Carbon Dioxide mean?
that is has 2 oxygen atoms
What does the ‘tri’ in Sulfur Trioxide mean?
That it has 3 oxygen atoms
Silicon has the symbol Si. What is the formula of silicon dioxide?
SiO2
When magnesium is heated with a Bunsen burner it forms magnesium oxide. Where do the oxygen atoms come from?
the air
Metal oxides are solids. One of the properties of metal oxides is that they act as bases. What does this mean?
that they are able to neutralise acids, producing a salt plus water.
Some metal oxides dissolve in water to make an alkali, a solution which has a pH higher than 7. Alkalis also neutralise acids to produce a salt plus water. True or False?
True
What is seen when magnesium burns in air?
A white flame
Acids react with most metals. What are the products when an acid reacts with a metal?
Salt and Hydrogen
What is the word equation for when a metal reacts with an acid?
Metal + Acid = Salt + Hydrogen
What would the pH of an acidic solution be?
pH below 7
What pH do acids which react with metals usually have?
pH less than 3
What is seen when a metal reacts with an acid?
- the metal getting smaller
- bubbles being produced
The name of the salt formed from the reaction of a metal and acid can be worked out using the names of the metal and the acid.
Name of metal + name of acid → salt name
What salt would be formed between Magnesium and Nitric Acid?
Magnesium nitrate
What salt would be formed between Calcium and Hydrochloric acid?
Calcium Chloride
Name 3 types of acid
Hydrochloric acid
Nitric acid
Sulfuric acid
What is the name of the salt formed when iron reacts with sulfuric acid?
Iron Sulfate
What salts would be formed from the reaction between Zinc and the following acids?:
Hydrochloric acid
Nitric acid
Sulfuric acid
1 - Zinc chloride
2 - Zinc nitrate
3 - Zinc sulfate
What type of salts are made from the reaction of sulfuric acid?
Sulfate
Nitrate salts are made from the reaction of which acid?
Nitric acid
What would we see if a sample of silver, gold or platinum is placed in acid? (think about where these metals are in the reactivity series)
No reaction
What would we see if a sample of potassium or sodium is placed in acid? (think about where these metals are in the reactivity series)
violent reaction
What are circuit diagrams used for?
to show how electrical components are connected in a circuit
What are Ammeters used for?
to measure the current flowing through components
What are Voltmeters used for?
To measure the potential difference across components
Which component provides power to a circuit?
A cell, battery or power supply
What unit is the current or flow of charge measured in?
Amps
An electrical current in a wire is a flow of what?
electrons
How are components, like motors, lamps and cells, represented in a circuit diagram?
circuit symbols represent each component
What is the difference between a battery and a cell?
A battery is made by connecting 2 or more cells together
What are the units of measurement of current?
Amperes (or Amps)
What are the units of measurement of potential difference?
Volts
What is used to measure current?
An ammeter
What is used to measure potential difference?
Voltmeter
How is an ammeter connected into a circuit?
In series, anywhere in the circuit
How is a voltmeter connected into a circuit?
in parallel with one lead on each side of the component
What is a series circuit?
when the components are all connected to the same loop
What is a parallel circuit?
when a component is on its own separate branch of the circuit e.g. a voltmeter
What is a sound wave?
a vibration that travels through a solid, liquid or gas such as the air or water
What type of sound has a large amplitude?
a loud sound
What type of sound has a high frequency?
a high pitched sound
How are sounds analysed?
Using waves traces
How are sounds made?
all sounds are made by something shaking or vibrating e.g. guitar string or drum
How does sound travel?
The air particles start vibrating and push on the air particles next to them, so the vibrations are passed on.
If you pluck a stretched rubber band hard, it makes a loud sound. If you pluck it gently, it makes a quiet sound. What does the loudness depend on?
how big the vibration of the air is
What type of wave is a sound wave?
A longitudinal wave
What is the lowest frequency a human can hear ?
20Hz
What is the highest frequency humans can hear ?
20,000 Hz
What scale are sound levels measured on?
Decibels (dB)
Too much noise can damage hearing. Exposure to 90 decibel sound levels for a long time can cause permanent hearing loss. Exposure to a brief sound level of 140 decibels will cause pain and can cause permanent damage to hearing. What is the typical decibel for background noise at home?
40dB
What is the typical decibel for whispering?
20dB
What is the typical decibel for normal talking?
60dB
Light travels as a _______ wave and can be reflected by surfaces and objects
transverse
What type of reflections do smooth shiny surfaces produce?
specular reflections
What type of reflections do rough surfaces produce?
diffuse reflections
What is a Ray diagram used for?
shows that path of a light ray being reflected from a plane mirror
What is the ray of light travelling towards the mirror called?
the incident ray
What is the ray of light travelling away from the mirror called?
the reflected ray
What is the dashed line called on a Ray diagram?
the normal - it is drawn 90 degrees to the surface of the mirror
What is the angle of incidence on a Ray diagram?
The angle between the normal, and the incident ray
What is the angle of reflection on a Ray diagram?
the angle between the normal, and the reflected ray
The angle the ray is reflected is always the same as the angle the light hits the mirror. True or False?
True
What happens to parallel light rays during specular reflection?
They are all reflected in the same direction
Which of these can produce clear images?
Specular reflection
Which type of diagram is used to show how images are formed by a mirror?
a Ray diagram
Light is refracted when it enters a material like water or glass. What does this mean?
light will reduce in speed as it travels through, causing it to change direction.
What can be used to show the path light takes when it is refracted?
a Ray diagram
The shape of a glass or plastic lens can affect the way it refracts light. True or False?
True
What does a converging lens do?
makes something look much larger
What objects use converging lenses?
Telescopes and magnifying glasses
- glasses for long sighted people
Looking through a glass block magnifies an object. True or false?
False - it stays the same like looking out of a window
What does a diverging (concave) lens do?
makes something look much smaller
What objects use diverging lenses?
Glasses (for short-sighted people)
Cameras used to take wide images like landscapes
What does a fish eye lens do?
makes something look spherical. e.g. skyscrapers in a city wouldn’t look straight but would curve into the top of the picture
Why does light refract?
Its speed changes
Which direction would light refract when travelling from air to glass?
Towards the normal
Which direction would light refract when travelling from air to glass?
Away from the normal
What is the angle of refraction?
The angle between the refracted ray and the normal
Does light travel faster in air or in glass?
Air
Which type of lens can be used to focus light to a point?
a convex lens
Why are lenses used to produce images?
To produce clear, focused images
Where would you find a convex lens?
In a camera
Why does the lens in your eye change shape?
To focus objects at different distances
What is static electricity?
It is a build-up of electrical charge on an object.
i.e. When objects become positively charged or negatively charged, usually because of friction between insulators.
What happens when you rub one neutral , electrically insulating object against another?
Some of the electrons are transferred across, leaving a negative charge on one of the objects, and a deficit on the other
What can static electricity cause?
- an electric shock
- it can cause objects to levitate, like making your hair stand on end
- it can cause attraction, like making a balloon stick to a wall
What are the 2 types of electrical charge?
positive and negative
What type of material allows electrical current to flow through it easily?
Conductor
Which type of material does not allow electrical current to flow through it easily?
Insulator
Which materials can be charged by friction?
Insulators
What is the term for an object which contains equal numbers of positive and negative charges?
Neutral
What type of charge does an electron have?
Negative
What happens when objects with the same static charge are near to each other?
They repel each other (push away from each other)
What happens when objects with the opposite static charge are near to each other?
They attract
Which type of charge can be easily transferred between insulators?
Negative
What might cause a neutral object to be attracted to a charged object?
Polarisation
When an atom loses an electron, which type of charge will the remaining ion have?
Positive
True or false? When current flows through a wire, it generates a magnetic field.
True
Which of these is NOT an advantage of an electromagnet?
- The strength can be changed
- It is always magnetic
- It can be switched off
- It can be reversed
It is always magnetic
Which of the following happens to an electromagnet when a soft iron core is added?
- the electromagnet doesn’t change
- The electromagnet reverses
- the electromagnet gets stronger
- the electromagnet gets weaker
the electromagnet gets stronger
What is the name of the coil of wire with many turns?
Solenoid
True or false? Motors and loudspeakers use the same effect to work.
True
In an electrical motor, what will happen if the current direction is reversed?
The direction of rotation will reverse
In an electrical motor, what will happen if both the flow of current is reversed and the permanent magnet is reversed?
Nothing will change
Which of these wouldn’t increase the strength of an electromagnet?
- coiling the wire
- adding a plastic core
- adding a soft iron core
- increasing the current
adding a plastic core
Which part of a loudspeaker causes the air to vibrate?
The cone
True or false? A microphone works in the same way as a loudspeaker.
False
How does an electromagnet work?
It uses a current to generate a magnetic field
What 3 things can strengthen an electromagnet?
- increasing the current
- increasing the number of turns in the coil
- adding an iron core
What can an electromagnet with a permanent magnet be used to make?
motors and loudspeakers
Any wire with a current running through it has a magnetic field. True or False?
True
The magnetic field around a wire with a current running through it are drawn as circles around the wire. What does it mean if the lines of these circles are closer together?
the magnetic field is stronger
What is a coil of wire with many turns called?
A Solenoid
What does a typical electromagnet consist of?
a wire coiled around an iron core
The iron core in an electromagnet is often called a soft iron core. Why?
because iron is magnetically soft - this means the iron is easy to magnetise and demagnetise
Where are electromagnets used?
- automatic door locks
- headphones
- scrap yard cranes
Electromagnets can be switched on and off. Why?
because they are only magnetic while a current is running through the coil
How can you increase the strength of an electromagnet?
- using a longer piece of wire so it has more turns on the coil
- using a bigger current
- adding a soft iron core - because iron is a magnetic material
In the motor effect, if two magnets of the same pole (e.g. north and north) are brought near to each other what happens?
they repel
In the motor effect, if two magnets of the opposite pole are brought near to each other (e.g. north and south), what happens?
they attract
What is the motor effect?
if you put a wire coil with a current going through it near a magnet it causes the wire to turn
