Units, measurements and working safely Flashcards
What must you always do when something is measured
State the units
Variable = Length
Measuring device used = Ruler, Tape measure, trundle wheel Units = meter (m), kilometer (km), mentimetre (cm), millimetre (mm)
Variable = Volume of liquid
Measuring device used = Measuring cylinder Units = Milliliters (ml), Liters (L)
Variable = Mass
Measuring device used = Balance Units = gram (g), kilogram (kg)
Variable = Temperature
Measuring device used = Thermometer Units = Degree Celsius (C)
Variable = Force
Measuring device used = Force meter (newton spring balance) Units = Newton (N)
Give examples of safety rules when doing an experiment
- Wear goggles or safety glasses, especially when handling or heating chemicals. - Wash your hands after handling chemicals, animals, plants, soils, etc. - Wipe up any spills immediately. - Never leave a flame, such as a candle or a Bunsen burner, unattended.
What units would be most appropriate to use to measure the following items? Mass of an Apple?
grams
Volume of a solution or liquid?
ml
Force taken to lift a pencil case ?
N
Width of the classroom
m
Length of a ladybird
mm
Peter is given two force meters. One measures from 0 – 10 N and one measures from 0 – 100 N. Which should he choose to measure as accurately as possible the force taken to pull a block (roughly 9 N)? explain
1 ) 0 - 10N 2) This scale will give a more accurate measurement because it is a smaller and more accurate scale size
Read the values
4.7
Read the value
52
What is a fair test
In a fair test you need to :
a) change one variable,
b) measure one variable and
c) keep all of the other variables the same.
What is a control?
In some investigations we have one part of the experiment that will be used as a comparison with the results of other parts.
e.g seed germination
where a control set of seeds is grown with water, oxygen,warmth and light
It is a good idea to repeat readings when doing an investigation?
Yes -
This allows you to check your results to see if they are reliable (repeatable). And so this is better than one single reading.
What key things do you need to think about when planning an investigation?
- what would be changed (independent variable) • what would be measured (dependent variable) • any key variables to be controlled
- what apparatus you would use and how (but keep it brief).
Rebecca wants to find out whether the floor surface affects the distance travelled by a toy car after it has run down a ramp.
What is the independent variable in her investigation (= what will she change)?
Independent variable is = Floor surface
Rebecca wants to find out whether the floor surface affects the distance travelled by a toy car after it has run down a ramp.
What is the dependent variable in her investigation (= what will she measure)?
Dependent variable = Distance travelled by the car
Rebecca wants to find out whether the floor surface affects the distance travelled by a toy car after it has run down a ramp.
Suggest two things she would need to keep the same to make it a fair test. (Remember to focus on things that would affect the result.)
1) Same toy car
2) Same ramp
Tamal wants to find out if the size of sugar crystals affects how quickly they dissolve. He puts the sugar into a beaker of water. He stirs the mixture and uses a timer to find out how long the sugar takes to dissolve.
What would Tamal need to do to make this a fair test? 4 marks
1) Same amout of water
2) same sugar
3) same temperature
4) stir at same speed
Describe how you could carry out an investigation to find out whether the length of people’s legs affects how quickly they can run? 4 marks
talk about same surface, distance, shoes, stopwatch
Some children want to make a catapult. They have some different widths of elastic and they want to find out which is best for the catapult.
(a) What might they choose as their dependent variable?
Dependent variable = distance of the stone thrown
Some children want to make a catapult. They have some different widths of elastic and they want to find out which is best for the catapult.
(a) If they choose this variable, what question are they investigating?
If the width of the elastic affects how far a stone can be flung.
Independent variable = width of elastic
