الأسبوع 10 · المحور الثاني «المادة والطاقة»، الوحدة الثانية «حركة الجسيمات»، المفهوم 2.2 «وصف المادة وطرق قياسها» (أ): خصائص المادة · 3 دروس
2
Grams, millilitres and degrees
Discovery Education Science P5: Term 1, Unit 2, pp. 152–157
GoalMeasure mass, volume and temperature with the right units.
New words
mass · the amount of matter in something, measured in g or kgvolume · the amount of space something takes up, measured in mL or Ltemperature · how hot or cold something is, measured in °C
Explanation
We measure matter in three ways. Mass is how much matter there is, and we measure it with a balance or a kitchen scale in grams (g) or kilograms (kg): 1 kg is 1000 g. Mass is not the same as weight. Volume is how much space something takes up. For a liquid we measure it in millilitres (mL) or litres (L): 1 L is 1000 mL. A solid with a regular shape has its volume in cubic centimetres, and 1 mL is the same as 1 cm³. Temperature tells how hot something is and is measured in degrees Celsius (°C) with a thermometer. A grown-up reads the thermometer when the water is hot. Always choose a sensible unit: a feather in grams, a bag of flour in kilograms, a spoon in millilitres.
We measure
Tool
Unit
mass
balance or scale
g, kg
volume
measuring jug
mL, L
temperature
thermometer
°C
Worked examples
kg
g
1
1000
2
2000
3
3000
Nada’s bag of rice has a mass of 2 kg. How many grams is that? 1 kg is 1000 g, so 2 × 1000 = 2000 g.
Liquid
Volume
juice
250 mL
water
500 mL
total
750 mL
A jug holds 1 L. Amir pours in 250 mL of juice and then 500 mL of water. The total is 250 + 500 = 750 mL, so there is room for 1000 − 750 = 250 mL more.
A grown-up reads the thermometer in a cup of warm water. The pointer is at 40 °C. Cold tap water is about 20 °C, so the warm water is 20 degrees warmer.
Class activity
Measuring station (a grown-up helps). Use a kitchen scale in grams to find the mass of three small things, such as a pencil, a coin and an apple. Use a measuring jug to measure 300 mL of water. Pour it into a taller, thinner cup and measure it again. A grown-up reads any hot thermometer. Record every result with its unit.
Practice
1
Which unit would you use for the mass of a pencil: g or kg?
Grams (g), because a pencil is very light.
2
A bag of flour is 3 kg. How many grams is that?
3 × 1000 = 3000 g.
3
You pour 400 mL of milk and 350 mL of water into one jug. What is the total volume?
