Science

• Spring


  A device that stores energy and can be used to measure force
• Balance


  An instrument used to measure mass
• The symbol for the standard SI unit of mass is kg
• Table 11.3 shows units of time
• The standard SI unit of time is the second, and its symbol is s
• Counting the first 50 words under the heading 'Accuracy of measurements'

  1. Count the first 50 words

  2. ii) Say those 50 words

  3. iii) Write down those 50 words
• Write down your estimate of the thickness of a page of this book and compare it with the estimates made by others. Are all the estimates the same? Explain what you discover.
• Accuracy and precision are important in collecting data in scientific enquiries
• A stop-watch that only measures time by seconds cannot be used to time events to a tenth of a second
• Care is needed in setting up the measuring device, such as placing a ruler accurately, resetting a stop-watch, and ensuring a balance is set at zero
• When using a balance with a scale read by a pointer, your eye should be positioned directly in front of the pointer
• At the beginning of an investigation, it may be useful to estimate quantities and time, as accuracy is not essential at this stage
• Quantities to estimate


  • Length of index finger
  • Length of thumb
  • Height of chair
  • Distance to a door
  • Mass of book
  • Mass of school bag and contents
  • Time to count 50 words
• The standard SI unit of mass is the kilogram, with symbol kg
• SI units of mass

  • tonne
  • megatonne
  • kilogram
  • gram
  • milligram
• Mass, length and time feature in describing a crime scene
• The standard SI unit of time is the second, with symbol s
• Physics is the scientific study of how matter and energy interact
• Every event in the universe is an interaction of matter and energy
• Physics can be described as the science of phenomena
• Launching a rocket


  1. Light from rocket engines seen

  2. Roar of engines heard

  3. Rocket speed increases

  4. Stages separate and fall back to Earth
• Length, mass and time are three things measured in many investigations
• SI units of length

  • kilometre
  • metre
  • centimetre
  • millimetre
  • micrometre
  • nanometre
• Precision means taking measurements a few times to check they stay the same
• Measurements must be taken until they are the same to become precise and reliable
• There are many tests made on materials, including measuring the strength by pulling until it tears and measuring the force
• Precision


  When a measurement stays the same, it is precise and can be used as a reliable source of data
• If the measurement varies then it is not precise and cannot be used as a reliable source of data
• Measuring precisely


  1. Take measurements until they are the same

  2. Measurements become precise and reliable
• Enquiry


  Test your ability to make precise measurements
• Can the speed of a liquid be measured precisely?
• Equipment needed


  • A slope made from a long, smooth piece of plastic or polished wood
  • A measuring cylinder
  • A bottle
• Material-testing laboratories test materials for many different properties using equipment to measure properties such as strength and electrical conductivity
• The data provided by these measurements help the manufacturers select materials which are particularly suitable for making their product
• Temperature


  The hotness or coldness of a substance
• Celsius scale


  The most widely used temperature scale, with fixed points at 0°C (melting point of ice) and 100°C (boiling point of water)
• The Celsius scale may be extended below 0°C and above 100°C, with laboratory thermometers usually having a scale reading from -10°C to 110°C
• As temperature increases


  The level of liquid in the thermometer tube rises
• As temperature decreases


  The level of liquid in the thermometer tube falls
• Absolute zero


  The lowest possible temperature, -273°C